CAP Profiles

Bio

Bio

A pioneer in the use of lasers to study chemical reactions at the molecular level, Marguerite Blake Wilbur Professor Richard N. Zare pursues diverse theoretical and experimental interests in physical chemistry and nanoscale chemical analysis. The Zarelab has made a broad impact in analytic chemistry with development of laser-induced fluorescence to study reaction dynamics, and seminal contributions to understanding of molecular collision processes. The group continues to invent tools and measurement techniques to study phenomena from reaction in microdroplets to drug delivery.

Born in 1939 in Cleveland, Ohio, Professor Zare trained in physical and analytical chemistry at Harvard University (B.A. 1961, Ph.D. 1964). His doctoral study under Professor Dudley Herschbach explored photodissociation dynamics. After faculty positions spanning chemistry at the Massachusetts Institute of Technology, chemistry, physics and astrophysics at the University of Colorado, and chemistry at Columbia University, he joined the Stanford chemistry faculty in 1977. He has taught an introductory chemistry class every year since. As a Howard Hughes Medical Institute Professor since 2006, Professor Zare has also developed a course introducing undergraduates to hands-on interdisciplinary research, combining physics, and biology to explore how living systems use molecular interactions with light for vision, photosynthesis and more. Professor Zare served as chair of the Department of Chemistry from 2005 to 2011, and has helped to guide scientific policy as chairman of several national and international science boards. His dedication to research and teaching has been recognized in many awards, including the National Medal of Science, the Wolf Prize in Chemistry, and the Presidential Award for Excellence in Science, Mathematics, and Engineering Mentoring. Among other honors, Professor Zare is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the American Philosophical Society. He has also received 11 honorary doctorates.

Current research in the Zarelab explores wide-ranging questions in physical and analytical chemistry, from the study of elementary chemical reactions to chemical analysis of extraterrestrial materials. The major focus of these efforts is chemical analysis on the nanoscale. The team has devised tools and techniques to examine molecules in extremely tiny volumes – the volumes characteristic of what is found in heterogeneous structures in mineral samples or in the contents of cells and subcellular compartments. Group members have also made contributions to the chemical analysis of liquid samples separated using a capillary format by electrophoresis or electrochromatography. Some “firsts” include the use of cavity ring-down spectroscopy to analyze trace species in solution, development of detectors for capillary electrophoresis based on the techniques of laser-induced fluorescence, and CCD imaging, and the use of mass spectrometric imaging of tissue samples by means of desorption electrospray ionization.

Please visit the Zarelab website to learn more: http://web.stanford.edu/group/Zarelab/

Academic Appointments

Administrative Appointments

  • Chair, Department of Chemistry, Stanford University (2006 - 2011)
  • Howard Hughes Medical Institute Professor, Stanford University (2006 - 2010)
  • Professor of Physics, Stanford University (1992 - Present)
  • Marguerite Blake Wilbur Professor in Natural Science, Stanford University (1987 - Present)
  • Fellow Adjoint, Joint Institute for Laboratory Astrophysics, University of Colorado (1985 - Present)
  • Stanford University Fellow, Stanford University (1984 - 1986)
  • Christensen Fellow, St. Catherine's College, Oxford University (1982 - 1982)
  • Shell Distinguished Professor of Chemistry, Stanford University (1980 - 1985)
  • Professor, Department of Chemistry, Stanford University (1977 - Present)
  • Higgins Professor of Natural Science, Columbia University (1975 - 1977)
  • Professor, Department of Chemistry, Columbia University (1969 - 1977)
  • Associate Professor, Department of Physics and Astrophysics and Department of Chemistry, University of Colorado (1968 - 1969)
  • Assistant Professor, Department of Physics and Astrophysics, University of Colorado (1966 - 1968)
  • Assistant Professor, Department of Chemistry, Massachusetts Institute of Technology (1965 - 1966)
  • Postdoctoral Research Associate, Joint Institute for Laboratory Astrophysics (JILA), University of Colorado (1964 - 1965)

Honors & Awards

  • National Medal of Science, National Science Foundation (1983)
  • Wolf Prize in Chemistry, Wolf Foundation, Israel (2005)
  • BBVA Foundation Frontiers of Knowledge Award in the Basic Sciences category, BBVA Foundation (2010)
  • King Faisal International Prize in Science, King Faisal Foundation (2011)
  • Presidential Award for Excellence in Science, Mathematics, and Engineering Mentoring (PAESMEM), U.S. Office of Science and Technology Policy (2009)
  • The Welch Award in Chemistry, The Welch Foundation (1999)
  • National Academy of Sciences Award in Chemical Sciences, National Academy of Sciences (1991)
  • American Chemical Society Award in Analytical Chemistry, American Chemical Society (1998)
  • Irving Langmuir Prize, American Physical Society (1985)
  • Peter Debye Award in Physical Chemistry, American Chemical Society (1991)
  • George C. Pimentel Award in Chemical Education, American Chemical Society (2008)
  • Priestley Medal, American Chemical Society (2010)
  • Honorary Doctorate, University of South Florida (2013)
  • The International Science and Technology Cooperation Award, The People's Republic of China (2012)
  • The World Academy of Sciences Lecture Medal, World Academy of Arts and Sciences (2012)
  • The Torbern Bergman Medal, The Swedish Chemical Society, The Analytical Division (2012)
  • Honorary Membership, Japan Society for Analytical Chemistry (JSAC) (2011)
  • Einstein Professorship, Chinese Academy of Sciences (2011)
  • R. B. Bernstein Award in Stereodynamics, International Symposium on Stereodynamics of Chemical Reactions (2010)
  • Honorary Fellow, Chinese Chemical Society (2010)
  • Theodore William Richards Medal, Northeastern Section of the American Chemical Society (2010)
  • F. A. Cotton Medal for Excellence in Chemical Research, Texas A&M University, Department of Chemistry, and Texas A&M Section, American Chemical Society (2009)
  • H. Julian Allen Award, NASA Ames Research Center (2007)
  • Dudley R. Herschbach Award, Dynamics of Molecular Collisions Meeting, Santa Fe, New Mexico (2007)
  • Honorary Doctorate, Chalmers Institute of Technology (2007)
  • Oesper Award, University of Cincinnati and Cincinnati Section of the American Chemical Society (2006)
  • Chandler Medal, Department of Chemistry, Columbia University (2005)
  • Pupin Medal "for service to the nation", Columbia University School of Engineering (2005)
  • Nichols Medal, New York Section of the American Chemical Society (2005)
  • James Flack Norris Award for Outstanding Achievement in the Teaching of Chemistry, Northeastern Section of the American Chemical Society (2004)
  • Laurance and Naomi Carpenter Hoagland Prize for Excellence in Undergraduate Education, Stanford University (2003)
  • Honorary Doctorate, Université Paul Sabatier, Toulouse, France (2003)
  • Distinguished Chemist Award, American Chemical Society Sierra Nevada Section (2002)
  • Honorary Doctorate, Hunan University (2002)
  • Scientific Achievement Award, California Separation Science Society (CaSSS) (2000 - 2001)
  • Madison Marshall Award, American Chemical Society, North Alabama (2000)
  • Honorary Doctorate, D Univ, The University of York (2001)
  • Honorary Doctorate, State University of West Georgia (2001)
  • Faraday Medal & Lectureship, Royal Society of Chemistry (2001)
  • Charles Lathrop Parsons Award, American Chemical Society (2001)
  • Nobel Laureate Signature Award for Graduate Education, American Chemical Society (2000)
  • Arthur L. Schawlow Prize in Laser Science, American Physical Society (2000)
  • Doctor of Philosophy, honoris causa, Uppsala University (2000)
  • Doctor of Science, honoris causa, Columbia University (1999)
  • E. Bright Wilson Award in Spectroscopy, The American Chemical Society (1999)
  • Distinguished Service Award, National Science Board (1998)
  • Centennial Medal, Graduate School of Arts and Sciences, Harvard University (1998)
  • G. M. Kosalapoff Award, Auburn Section, American Chemical Society (1998)
  • Eastern Analytical Symposium Award for Outstanding Achievements in the Field of Analytical Chemistry, Eastern Analytical Symposium (1997)
  • Allan V. Cox Medal for Faculty Excellence Fostering Undergraduate Research, Stanford University (1997)
  • NASA Exceptional Scientific Achievement Award, NASA (1997)
  • Phi Beta Delta (Honorary Member), Phi Beta Delta (1997)
  • California Scientist of the Year, California Science Center (1997)
  • The Bing Fellowship Award, Stanford University (1996)
  • ACS Division of Analytical Chemistry Award in Chemical Instrumentation, ACS Division of Analytical Chemistry (1995)
  • Dannie-Heineman Preis, Akademie der Wissenschaften zu Göttingen (1993)
  • Doctor of Science, Honorary Degree, Eidgenössische Technische Hochschule Zürich (1993)
  • The Pauling Award, Puget Sound, Oregon and Portland Sections of the American Chemical Society (1993)
  • The Harvey Prize, Technion, Israel Institute of Technology (1993)
  • Doctor of Science, Honorary Degree, Northwestern University (1993)
  • Willard Gibbs Medal, Chicago Section, American Chemical Society (1990)
  • Doctor of Science, Honorary Degree, University of Arizona (1990)
  • ISCO Award for Significant Contributions to Instrumentation for Biochemical Separations, International Stem Cell Corporation (ISCO) (1990)
  • Dean's Award for Excellence in Teaching, Stanford University (1987)
  • Kirkwood Award Medal, Yale University, New Haven Section of the American Chemical Society (1986)
  • Michelson-Morley Award, Case Institute of Technology, Case Western Reserve University (1986)
  • Harrison Howe Award, Rochester Section, American Chemical Society (1985)
  • Remsen Award, Maryland Section, American Chemical Society (1985)
  • Evans Award, The Ohio State University (1984)
  • Spectroscopy Society of Pittsburgh Award, Spectroscopy Society of Pittsburgh (1983)
  • Earle K. Plyler Prize, American Physical Society (1981)
  • Michael Polanyi Medal, The Royal Society of Chemistry (1979)
  • Fresenius Award, Phi Lambda Upsilon Honorary Chemical Society (1974)
  • Alfred P. Sloan Fellowship, Alfred P. Sloan Foundation (1967 - 1969)
  • Phi Beta Kappa award, Phi Beta Kappa Society (1961)
  • Honorary Professor, Nanjing University
  • Honorary Professor, Xiamen University
  • Honorary Professor, Tsinghua University
  • Honorary Professor, Dalian Institute of Chemical Physics
  • Honorary Professor, University of Science and Technology of China
  • Honorary Professor, Beijing Institute of Technology
  • Honorary Professor, Institute of Chemistry Chinese Academy of Sciences
  • Honorary Professor, Zeijiang University
  • Honorary Professor, China Central Normal University
  • Honorary Professor, Hunan University
  • Honorary Professor, Changchun Institute of Applied Chemistry
  • Honorary Professor, Shanghai Jiao Tong University
  • Phillip W. West Lecture, Louisiana State University (2014)
  • Pegram Lectures, Brookhaven National Laboratory, Upton, New York (2014)
  • Fred M. Weissman Lecture in Analytical Chemistry, University of South Carolina, Columbia, South Carolina (2014)
  • Wilhelm Jost Memorial Lectures, Freie Universität; Gottfried Wilhelm Leibniz Universität; Georg-August-Universität, Germany (2014)
  • Centenary Lecture, Indian Institute of Science (IISc), Bangalore, India (2014)
  • CV Raman Lecture, Indian Association for the Cultivation of Science (IACS), Kolkata, India (2014)
  • Homi Bhabha Lecture, Tata Institute for Fundamental Research (TIFR), Mumbai, India (2014)
  • Heaven and Earth Distinguished Lectures, Nanjing University, China (2013)
  • James S. Plant Distinguished Lecture, Hamilton College, Clinton, New York (2013)
  • Plenary Lecture, Wu Chien-Shiung Science Summer Camp, Xitou, Taiwan (2013)
  • New Biology Distinguished Lecture, DGIST, Daegu, South Korea (2013)
  • Jackson Lecture, University of Florida, Gainesville, Florida (2013)
  • Martin Lecture, University of South Florida, Tampa, Florida (2013)
  • Svedberg Lecture, Uppsala University, Uppsala, Sweden (2013)
  • Linnett Visiting Professor Lectureship, Department of Chemistry, University of Cambridge, Cambridge, UK (2013)
  • Lady Margaret Lecture, Christ's College, University of Cambridge, Cambridge, UK (2013)
  • Department of Chemical Engineering, Tsinghua University, Beijing, China (2013)
  • Department of Chemistry, Beijing Institute of Technology, Beijing, China (2013)
  • Shipley Lecture, Department of Chemistry, Clarkson University (2013)
  • Teickmann Lecture, SUNY Buffalo (2013)
  • Bangalore Science Forum, Bangalore, India (2014)
  • Visva-Bhrati University, Santiniketan, India (2014)
  • King Abdullah University of Science and Technology (KAUST), Saudi Arabia  (2014)
  • ISIC Seminar, Ecole Polytechnique Fédérale de Lausaunne, Switzerland (2012)
  • Jean Dreyfus Boissevain Lecture,, Bucknell University, Lewisburg, PA  (2012)
  • Izatt-Christensen Lecturer, Bringham Young University (2012)
  • Plenary Lecture, Celebration of Chemistry, IITK, Indian Institute of Technology Kanpur (2011)
  • Plenary Lecture, The Third Asian Spectroscopy Conference, Science and Art Center, Xiamen Uninversity (2011)
  • Wynne-Jones Memorial Lecture, University of Newcastle (2011)
  • Plenary Lecture, IUPAC International Congress on Chemical Sciences, Kyoto, Japan (2011)
  • Salomon Bochner Lecture, Scientia,, Rice University (2011)
  • The Thirtieth Annual Barnett Lectureship, Northeastern, The Barnett Institute of Chemical and Biological Analysis (2011)
  • Distinguished Lecture Series in Mathematical and Physical Sciences, National Science Foundation (2011)
  • 22nd Annual Frontiers in Chemistry Symposium, The Scripps Research Institute (2011)
  • Plenary Lecture, Year of Chemistry, Uppsala University (2011)
  • Wolf Prize Foundation Laureate Lecture, International Symposium "Frontiers in Photon Science", University of Manchester (2010)
  • Plenary Lecture, 45º Congreso Mexicano de Química y 29º Congreso Nacional de Educación, Química, Riviera Maya, Quintana Roo, Mexico (2010)
  • Vail Lectures, Wake Forest University (2010)
  • Plenary Lecture, International Conference on Chemical Education, Taipei, Taiwan (2010)
  • Global Vision Lecture, Tsinghua University, Beijing, China (2010)
  • Plenary Lecture, Chemistry Division,, Chinese Academy of Sciences, Beijing, China (2010)
  • Plenary Lecture, 4th International Symposium on Bioanalysis, Changsha, China (2010)
  • C. R. Mueller Memorial Lecture,, Purdue University (2010)
  • Plenary Lecture, Academia Sinica, Taipei, Taiwan (2010)
  • Plenary Lecture, Isranalytica, Tel Aviv, Israel (2010)
  • MTSU Distinguished Lecture, Middle Tennessee State University (2009)
  • NanQiang Lecture, Xiamen University, Xiamen, China (2009)
  • Rajiv Gandhi Science and Technology Lecture, Bangalore, India (2009)
  • Dr. Emily Davis and Dr. Homer C. Weed Lecture, Department of Chemistry and Biochemistry, University of Arizona (2009)
  • A. R. Gordon Distinguished Lectures Series, University of Toronto, Toronto, Canada (2009)
  • Abbott Chemistry Lectures, University of North Dakota (2009)
  • Phyllis Johnson Patrick Lecture,, Kansas State University (2009)
  • Platinum Jubilee Lecture, Indian Academy of Sciences, Bangalore University, Bangalore, India (2009)
  • Robert S. Mulliken Lecture, University of Georgia (2008)
  • Leland Wilson Endowed Lecture, University of Northern Iowa (2008)
  • Frank Whitmore Lecture, The Pennsylvania State University (2008)
  • Helen Murray Free Endowed Lecture, University of Wooster (2008)
  • Plenary Lecture, 10th National Symposium, Chemical Research Society of India, Bangalore, India (2008)
  • William A. Chupka Lectureship in Physical and Theoretical Chemistry, Yale University (2007)
  • The Arnold C. Ott Lectureship in Chemistry, Grand Valley State University (2007)
  • 3M/Ronald A. Mitsch Lecture in Chemistry, Hamline University (2007)
  • 18th Leopold Marcus Lecture, Department of Chemistry, Washington University in St. Louis (2007)
  • Nobel Laureates 2007 Beijing Forum on Energy and the Environment, Beijing, China (2007)
  • Plenary Lecture, Ninth Annual Beckman Scholars Symposium, Irvine, California (2007)
  • Roberts Lecturer, University College, London, UK (2007)
  • Distinguished Frontiers Speaker, University of Toledo (2007)
  • Ritter Memorial Lectures, Miami University of Ohio (2007)
  • Keynote Speaker, Honors Week Celebration, Kent State University (2007)
  • Morino Lectures, University of Tokyo and Kyoto University, Japan (2007)
  • Plenary Speaker, New Zealand Institute of Chemistry Conference, Rotorua, New Zealand (2006)
  • Sir Neil Waters Distinguished Lectureship, Massey University, Palmerston North, New Zealand (2006)
  • Michael Faraday Lecture, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India (2006)
  • Mission Bay Seminar, University of California at San Francisco (2006)
  • Cal Giddings Lecture, University of Utah (2006)
  • Keynote Lecture, Biennial Conference on Chemical Education (BCCE), Purdue University (2006)
  • Plenary Lecture, International Workshop on Bioanalytical Chemistry and Biomedical Engineering, Hunan University, Changsa, China (2010)
  • Distinguished Zhang Dayu Lecture, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China (2006)
  • Lectures in Modern Chemistry, Department of Chemistry,, University of British Columbia, Vancouver, BC, Canada (2006)
  • Spring Colloquium Speaker, Department of Chemistry & Biochemistry, University of Washington (2006)
  • Frontiers in Chemical Research Lecturer, Texas A & M University (2006)
  • G. Wilse Robinson Lecturer, Texas Tech University (2006)
  • Vessman Lecture, Chalmers University, Göteborg, Sweden (2006)
  • Plenary Speaker, Photon Science Institute Launch, University of Manchester, Manchester, UK (2006)
  • Purves Lecturer, McGill University, Montreal, Canada (2005)
  • Plenary Speaker, Federation of Analytical Chemistry and Spectroscopy Societies (FACCS), Quebec City, Canada (2005)
  • Plenary Speaker, ScotCHEM Launch, Edinburgh, Scotland (2005)
  • Plenary Speaker, CONNECT 2005, 12th Royal Australian Chemical Institute (RACI) National Convention, Sydney, Australia (2005)
  • PECRUM Lecturer (Perspective on Chemistry Research), University of Michigan) (2005)
  • Keynote Speaker, Atlanta Undergraduate Research Alliance (AURA) (2005)
  • Arthur D. Little Lecturer, Massachusetts Institute of Technology (2004)
  • William E. Mahoney Lecturer, University of Massachusetts Amherst (2004)
  • Mitchum E. Warren, Jr. Lecturer, Department of Chemistry, Vanderbilt University (2004)
  • Robert A. Jenkins Memorial Lecturer, Department of Chemistry, University of Wyoming (2004)
  • Charles Herron Lecturer, Department of Chemistry and Biochemistry, Florida State University (2004)
  • Noyes Lecturer, Department of Chemistry, University of Oregon (2004)
  • Plenary Lecturer, Singapore International Chemistry Conference 3, Singapore (2003)
  • S. Dexter Squibb Distinguished Lecturer, Department of Chemistry, University of North Carolina (2003)
  • Haberman Lecturer, Department of Chemistry, Marquette University (2002)
  • Samuel M. McElvain Seminar, Department of Chemistry, University of Wisconsin-Madison (2002)
  • George Gamow Memorial Lecture, University of Colorado at Boulder (2002)
  • L. Carroll King Memorial Lectures, Department of Chemistry, Northwestern University (2001)
  • R. T. Majors Lecturer, Department of Chemistry, University of Connecticut (2001)
  • Flygare Memorial Lecturer, Department of Chemistry, University of Illinois at Urbana-Champaign (2001)
  • Hirschmann Lecturer, Oberlin College (2000)
  • Carr Lecturer, Department of Chemistry, Coe College (2000)
  • Manuel G. Menendez Memorial Lecturer, Department of Physics and Astronomy, University of Georgia (2000)
  • Anderson Lecture, Department of Physics and Astronomy, Denison University (2000)
  • The Timothy J. O’Leary, S. J. Distinguished Scientist Lecturer, Science Departments of Gonzaga University (2000)
  • Lyle Ramsay Dawson Lecturer, Department of Chemistry, University of Kentucky (1999)
  • S. C. Lind Lecture, East Tennessee Section of the American Chemical Society (1999)
  • Charles M. Knight Lecturer, Department of Chemistry, The University of Akron (1999)
  • The O. K. Rice Lecturer, Department of Chemistry, The University of North Carolina at Chapel Hill (1999)
  • The Lloyd B. Thomas Chemistry Scholars Lecturer, Department of Chemistry, University of Missouri (1999)
  • The Joe L. Franklin Memorial Lecture, Department of Chemistry, Rice University (1999)
  • Harry Emmett Gunning Lecturer, Department of Chemistry, University of Alberta (1998)
  • Clifford C. Hach Lecturer, Department of Chemistry, University of Wyoming (1998)
  • Barre Lecturer, University of Montreal, Canada (1998)
  • Kosalopoff Lecturer, Auburn University (1998)
  • Centenary Lecturer, Royal Society of Chemistry (1998)
  • Anson L. Clark Memorial Lecturer, University of Texas at Dallas (1998)
  • Billings Distinguished Lecturer, Montana State University (1998)
  • Claude Worthington Benedum Foundation Lecturer, West Virginia University (1997)
  • Robert Maurer Lecture, Department of Physics, University of Arkansas (1997)
  • Frank G. and Jean M. Chesley Lectureship, Carleton College (1997)
  • Jacob Bigeleisen Endowed Lecture, State University of New York Stony Brook (1996)
  • Gooch-Stephens Lectureship, Baylor University (1996)
  • DuPont Distinguished Speaker, Indiana University (1996)
  • G.B. Kistiakowsky Lecturer, Harvard University (1996)
  • Alexander M. Cruickshank Lecturer, Gordon Research Conference (1996)
  • Leroy Eyring Lecturer, Arizona State University (1995)
  • Velmer Fassel Lecturer, Iowa State University (1995)
  • Richard C. Lord Lecturer, Massachusetts Institute of Technology (1995)
  • Fred J. Robbins Lecturer, Pomona College (1995)
  • Moses Gomberg Lecturer, University of Michigan (1995)
  • Lemieux Lecturer, University of Ottawa (1995)
  • Frederic LeRoy Conover Memorial Lecturer, Vanderbilt University (1994)
  • Raymond Lemieux Lecturer, University of Ottawa (1994)
  • Peter Smith Lecturer, Duke University (1994)
  • Paul C. Cross Lecturer, University of Washington (1993)
  • Linus Pauling Distinguished Lecturer, Oregon State University (1993)
  • R.B. Bernstein Memorial Lecturer, UCLA (1993)
  • Nalbandov Lecturer, University of Illinois (1993)
  • George C. Pimental Lecturer, UC Berkeley (1992)
  • Robert S. Mulliken Lecturer, University of Chicago (1992)
  • Arthur D. Little Lecturer, Northeastern University (1991)
  • J. T. Donald Lecturer, McGill University (1991)
  • Frederick Kaufman Lecturer, University of Pittsburgh (1991)
  • Peter A. Leermakers Symposium Lecturer, Wesleyan University (1991)
  • Russell Marker Lecturer in the Chemical Sciences, Pennsylvania State University (1991)
  • Ernest H. Swift Lecturer, California Institute of Technology (1991)
  • Amy/Mellon Lecturer, Purdue University (1990)
  • Distinguished Scientists Lecturer, Trinity University (1990)
  • E. K. C. Lee Lecturer, University of California at Irvine (1989)
  • Geoffrey Frew Fellow, Australian Academy of Sciences (1989)
  • Max T. Rogers Lecturer, Michigan State University (1989)
  • Joel Broberg Lecturer in Chemistry, North Dakota State University (1989)
  • Gustavson Lecturer, University of Denver (1989)
  • Kennedy Lecturer, Washington University, St. Louis (1989)
  • John Albert Southern Lecturer, Furman University (1989)
  • Distinguished Visiting Lecturer, University of Texas at Austin (1989)
  • Procter and Gamble Lecturer, University of Illinois at Champaign- Urbana (1988)
  • Xerox Lecturer, Simon Fraser University (1988)
  • Marvel-Monsanto Lecturer, University of Arizona (1988)
  • Appleton Lecturer, Brown University (1988)
  • Walter J. Chute Distinguished Lecturer, Dalhousie University (1987)
  • Edgar Fahs Smith Lecturer, University of Pennsylvania (1987)
  • Charles A. McDowell Lecturer in Chemical Physics, University of British Columbia (1987)
  • Weizmann Memorial Lecturer, Weizmann Institute, Rehovot, Israel (1986)
  • Friend E. Clark Lecturer, West Virginia University (1986)
  • Fritz London Memorial Lecturer, Duke University (1986)
  • Merck Distinguished Lecturer, Rutgers University (1986)
  • "Frontiers of Science" Distinguished Visiting Professor, University of Florida (1986)
  • Camille and Henry Dreyfus Lecturer, Dartmouth College (1985)
  • Davis Lecturer, University of New Orleans (1985)
  • Priestley Lecturer, Pennsylvania State University (1985)
  • Coover Lecturer, Iowa State University (1985)
  • Francis E. Blacet Lecturer, University of California at Los Angeles (1985)
  •   Plenary Lecturer, Lasers '84 (1984)
  • John E. Willard Lecturer, University of Wisconsin (1984)
  • Evans Lecturer, Ohio State University (1984)
  • "Frontiers in Chemical Research" Distinguished Lecturer, Texas A&M University (1984)
  • Distinguished Scientist Lecturer, University of Arizona (19983)
  • ICPEAC Plenary Lecturer, XIII International Conference on the Physics of Electronic and Atomic Collisions, Berlin, Germany (1983)
  • William Draper Harkins Lecturer, University of Chicago (1983)
  • Falk-Plaut Lecturer, Columbia University (1983)
  • Dreyfus Scholar in Residence, Hope College (1982)
  • Venable Lecturer, University of North Carolina (1982)
  • Albert W. Noyes Lecturer, University of Texas at Austin (1982)
  • Jeremy Musher Memorial Lecturer, Hebrew University (1982)
  • Guggenheim Lecturer, Reading University (1982)
  • Hinschelwood Lecture, Oxford University (1982     )
  • Research Scholar, Drew University (1981)
  • University Professor, University of Arkansas (1981)
  • Honor Lecturer in Chemistry, Arizona State University (1981)
  • McGregor Lecturer, Colgate College (1980)
  • Baker Lecturer, Cornell College (1980)
  • Kolthoff Lecturer, University of Minnesota (1980)
  • William Pyle Philips Lecturer in Chemistry, Haverford College (1980)
  • Frank T. Gucker Lecturer in Chemistry, Indiana University (1979)
  • Peter C. Reilly Lecturer, University of Notre Dame (1979)
  • Francis Clifford Phillips Lecturer, University of Pittsburgh (1979)
  • Distinguished Visiting Professor, Michigan State University (1978)
  • Edward U. Condon Lecturer in Chemical Physics, University of Colorado (1977)
  • Distinguished University Lecturer, University of Utah (1977)
  • Sherwin Williams Lecturer, University of Illinois (1977)
  • Frontiers in Chemistry Lecturer, Wayne State University (1977)
  • Westinghouse Invited Lecturer in Chemistry, Pittsburgh, Pennsylvania (1976)
  • Arthur D. Little Visiting Professor, Massachusetts Institute of Technology (1972)
  • Harold Herborg Nielsen Lecturer, Ohio State University (1975)
  • FMC Lecturer, Princeton University (1976)

Boards, Advisory Committees, Professional Organizations

  • Member, Board of Trustees Committee, Stanford University (2014 - Present)
  • Chair, COSEPUP (Committee on Science, Engineering, and Public Policy) of the three Academies (2012 - Present)
  • Member, Advisory Board, School of New Sciences, DGIST, Daegu, South Korea (2012 - Present)
  • Director of International Advisory Board, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University (2012 - Present)
  • Fellow, TWAS, Academy of Sciences for the Developing World (2009 - Present)
  • Fellow, American Chemical Society (2009 - Present)
  • Member of the Board of Directors, Camille and Henry Dreyfus Foundation (2009 - Present)
  • Honorary Fellow, Indian Academy of Sciences (2008 - Present)
  • Fellow, Association for Women in Science (2008 - Present)
  • Chairman, Board of Directors, Annual Reviews Inc. (1995 - Present)
  • Honorary Fellow, Chemical Research Society of India (CRSI) (2007 - Present)
  • Senior Presidential Advisor, Hunan University (2006 - Present)
  • President, Molecular Frontiers Foundation (2006 - 2011)
  • Chair, Academic Advisory Committee, Biomedical Engineering Center, Hunan University (2006 - Present)
  • Member, European Academy of Sciences (2004 - Present)
  • Foreign Member, Swedish Royal Academy of Engineering Sciences (IVA) (2004 - Present)
  • Foreign Member, Chinese Academy of Sciences (CAS) (2004 - Present)
  • Honorary Member, The World Jewish Academy of Sciences (2004 - Present)
  • Honorary Fellow, Royal Society of Chemistry (2001 - Present)
  • Foreign Member, Royal Society (London) (1999 - Present)
  • Fellow, California Council on Science and Technology (1997 - Present)
  • Honorary Fellow, California Academy of Sciences (1991 - Present)
  • Fellow, Optical Society of America (1991 - Present)
  • Member, American Philosophical Society (1991 - Present)
  • Fellow, American Association for the Advancement of Science (1985 - Present)
  • Member, National Academy of Sciences (1976 - Present)
  • Member, American Academy of Arts and Sciences (1976 - Present)
  • Fellow, The American Physical Society (1969 - Present)
  • Non-Resident Fellow, Joint Institute of Laboratory Astrophysics (1969 - Present)
  • Member, The Chemical Society (London) (1969 - Present)
  • Member, Editorial Advisory Board, Angewandte Chemie
  • Member, Advisory Board, DGIST (2015 - Present)
  • Member, Executive Committee, Board of Directors, Wonderfest, Inc. (2011 - 2014)
  • Chair, International Evaluation Committee, National Science Foundation of China (2010 - 2012)
  • Fellow, Michelle R. Clayman Institute for Gender Research (2008 - 2008)
  • Advisor, Camille and Henry Dreyfus Foundation (2007 - 2009)
  • Faculty Affiliate, Michelle R. Clayman Institute for Gender Research (2006 - 2008)
  • Foreign Council Member, Institute for Molecular Science (Japan) (1999 - 2001)
  • Chairman, President’s National Medal of Science Selection Committee (1997 - 2000)
  • Council Member, National Academy of Sciences (1995 - 1998)
  • Member, National Science Board (1992 - 1998)
  • Chairman, National Science Board (1996 - 1998)
  • Chair, Commission on Physical Sciences, Mathematics, and Applications, National Research Council (1992 - 1995)
  • Vice-Chair, Board of Directors, Annual Reviews, Inc. (1992 - 1995)
  • Member, Government-University-Industry Research Roundtable of the National Academy of Sciences (1989 - 1992)
  • Chairman, Panel on Basic Science and Technology Centers, National Academy of Sciences (1987 - 1987)
  • Member, Directed Energy Weapons study panel, American Physical Society (1985 - 1987)
  • Chairman, Division of Chemical Physics (DCP) American Physical Society (1985 - 1986)
  • Vice-Chairman, Division of Chemical Physics (DCP), American Physical Society (1984 - 1985)
  • Member, Committee on Atomic and Molecular Science (CAMS), National Research Council (1983 - 1985)
  • Editor, Chemical Physics Letters (1982 - 1985)
  • Chairman, National Science Foundation Advisory Panel (Chemistry Division) (1980 - 1982)
  • Member, Editorial Advisory Board, Current Science (2014 - Present)
  • Member, Editorial Advisory Board, Chemistry World
  • Honorary Board Member, Editorial Advisory Board, Physical Chemistry and Chemical Physics (PCCP)
  • Member, Editorial Advisory Board, Analytical Sciences
  • Member, Editorial Advisory Board, Central European Journal of Chemistry
  • Member, Editorial Advisory Board, ChemPhysChem
  • Member, Editorial Advisory Board, Chemical Physics
  • Member, Editorial Advisory Board, Chemical Physics Letter
  • Member, Editorial Advisory Board, Molecular Physics
  • Member, Editorial Advisory Board, Journal of Separation Sciences
  • Member, Editorial Advisory Board, Chinese Journal of Chromatography
  • Member, Editorial Advisory Board, Brainwave
  • Member, Editorial Advisory Board, Chromatography
  • Member, Board of Editors, The Journal of Molecular Spectroscopy
  • Member, Board of Editors, Science
  • Member, Board of Editors, Cambridge University Press
  • Member, Board of Editors, Applied Physics
  • Member, Board of Editors, Accounts of Chemical Research
  • Member, Board of Editors, Analytical Chemistry
  • Member, Board of Editors, Chemical & Engineering News
  • Member, Board of Editors, The Journal of Chemical Physics
  • Member, Board of Editors, The Journal of Physical Chemistry
  • Member, Board of Editors, Optics Letters
  • Member, Scientific Advisory Board, Pufendorf Institute, Lund University
  • Member, International Advisory Board, State Key Laboratory of Physical Chemistry of Solid Surfaces (PCOSS)
  • Member, Scientific Advisory Board, Hybrid Vigor Institute
  • Member, Scientific Advisory Board, Fluidigm
  • Member, Scientific Advisory Board, Eksigent, Inc.
  • Member, Scientific Advisory Board, Pharmacyclics, Inc.
  • Member, Scientific Advisory Board, Prolinx, Inc.
  • Member, Scientific Advisory Board, Cepheid, Inc.
  • Member, Scientific Advisory Board, Picarro
  • Member, Scientific Advisory Board, Wonderfest
  • Member, Scientific Advisory Board, Advisory Council for Chemistry at Oxford
  • Member, Scientific Advisory Board, Electronic Nobel Museum/Young Scholars Program
  • Member, Scientific Advisory Board, Faraday Transactions
  • Member, Scientific Advisory Board, Quanta-Ray
  • Member, Scientific Advisory Board, Affymax, Inc.
  • Member, Scientific Advisory Board, Miller Institute
  • Member, Scientific Advisory Board, IBM

Professional Education

  • PhD, Harvard University (NSF Predoctoral Fellow), Chemical Physics (1964)
  • Postgraduate work, University of California at Berkeley (1963)
  • BA, Harvard University, Chemistry and Physics (1961)

Contact

Links

Research & Scholarship

Current Research and Scholarly Interests

My research group is exploring a variety of topics that range from the basic understanding of chemical reaction dynamics to the nature of the chemical contents of single cells.

Under thermal conditions nature seems to hide the details of how elementary reactions occur through a series of averages over reagent velocity, internal energy, impact parameter, and orientation. To discover the effects of these variables on reactivity, it is necessary to carry out studies of chemical reactions far from equilibrium in which the states of the reactants are more sharply restricted and can be varied in a controlled manner. My research group is attempting to meet this tough experimental challenge through a number of laser techniques that prepare reactants in specific quantum states and probe the quantum state distributions of the resulting products. It is our belief that such state-to-state information gives the deepest insight into the forces that operate in the breaking of old bonds and the making of new ones.

Space does not permit a full description of these projects, and I earnestly invite correspondence. The following examples are representative:

The simplest of all neutral bimolecular reactions is the exchange reaction H H2 -> H2 H. We are studying this system and various isotopic cousins using a tunable UV laser pulse to photodissociate HBr (DBr) and hence create fast H (D) atoms of known translational energy in the presence of H2 and/or D2 and using a laser multiphoton ionization time-of-flight mass spectrometer to detect the nascent molecular products in a quantum-state-specific manner by means of an imaging technique. It is expected that these product state distributions will provide a key test of the adequacy of various advanced theoretical schemes for modeling this reaction.

Analytical efforts involve the use of capillary zone electrophoresis, two-step laser desorption laser multiphoton ionization mass spectrometry, cavity ring-down spectroscopy, and Hadamard transform time-of-flight mass spectrometry. We believe these methods can revolutionize trace analysis, particularly of biomolecules in cells.

Teaching

2019-20 Courses

Stanford Advisees

Publications

All Publications

  • Spontaneous generation of hydrogen peroxide from aqueous microdroplets. Proceedings of the National Academy of Sciences of the United States of America Lee, J. K., Walker, K. L., Han, H. S., Kang, J., Prinz, F. B., Waymouth, R. M., Nam, H. G., Zare, R. N. 2019

    Abstract

    We show H2O2 is spontaneously produced from pure water by atomizing bulk water into microdroplets (1 mum to 20 m in diameter). Production of H2O2, as assayed by H2O2-sensitve fluorescence dye peroxyfluor-1, increased with decreasing microdroplet size. Cleavage of 4-carboxyphenylboronic acid and conversion of phenylboronic acid to phenols in microdroplets further confirmed the generation of H2O2 The generated H2O2 concentration was 30 M (1 part per million) as determined by titration with potassium titanium oxalate. Changing the spray gas to O2 or bubbling O2 decreased the yield of H2O2 in microdroplets, indicating that pure water microdroplets directly generate H2O2 without help from O2 either in air surrounding the droplet or dissolved in water. We consider various possible mechanisms for H2O2 formation and report a number of different experiments exploring this issue. We suggest that hydroxyl radical (OH) recombination is the most likely source, in which OH is generated by loss of an electron from OH- at or near the surface of the water microdroplet. This catalyst-free and voltage-free H2O2 production method provides innovative opportunities for green production of hydrogen peroxide.

    View details for DOI 10.1073/pnas.1911883116

    View details for PubMedID 31451646

  • The MYC Oncogene Cooperates with Sterol-Regulated Element-Binding Protein to Regulate Lipogenesis Essential for Neoplastic Growth. Cell metabolism Gouw, A. M., Margulis, K., Liu, N. S., Raman, S. J., Mancuso, A., Toal, G. G., Tong, L., Mosley, A., Hsieh, A. L., Sullivan, D. K., Stine, Z. E., Altman, B. J., Schulze, A., Dang, C. V., Zare, R. N., Felsher, D. W. 2019

    Abstract

    Lipid metabolism is frequently perturbed in cancers, but the underlying mechanism is unclear. We present comprehensive evidence that oncogene MYC, in collaboration with transcription factor sterol-regulated element-binding protein (SREBP1), regulates lipogenesis to promote tumorigenesis. We used human and mouse tumor-derived cell lines, tumor xenografts, and four conditional transgenic mouse models of MYC-induced tumors to show that MYC regulates lipogenesis genes, enzymes, and metabolites. We found that MYC induces SREBP1, and they collaborate to activate fatty acid (FA) synthesis and drive FA chain elongation from glucose and glutamine. Further, by employing desorption electrospray ionization mass spectrometry imaging (DESI-MSI), we observed invivo lipidomic changes upon MYC induction across different cancers, for example, aglobal increase in glycerophosphoglycerols. After inhibition of FA synthesis, tumorigenesis was blocked, and tumors regressed in both xenograft and primary transgenic mouse models, revealing the vulnerability of MYC-induced tumors to the inhibition of lipogenesis.

    View details for DOI 10.1016/j.cmet.2019.07.012

    View details for PubMedID 31447321

  • Early detection of unilateral ureteral obstruction by desorption electrospray ionization mass spectrometry. Scientific reports Banerjee, S., Wong, A. C., Yan, X., Wu, B., Zhao, H., Tibshirani, R. J., Zare, R. N., Brooks, J. D. 2019; 9 (1): 11007

    Abstract

    Desorption electrospray ionization mass spectrometry (DESI-MS) is an emerging analytical tool for rapid in situ assessment of metabolomic profiles on tissue sections without tissue pretreatment or labeling. We applied DESI-MS to identify candidate metabolic biomarkers associated with kidney injury at the early stage. DESI-MS was performed on sections of kidneys from 80 mice over a time course following unilateral ureteral obstruction (UUO) and compared to sham controls. A predictive model of renal damage was constructed using the LASSO (least absolute shrinkage and selection operator) method. Levels of lipid and small metabolites were significantly altered and glycerophospholipids comprised a significant fraction of altered species. These changes correlate with altered expression of lipid metabolic genes, with most genes showing decreased expression. However, rapid upregulation of PG(22:6/22:6) level appeared to be a hitherto unknown feature of the metabolic shift observed in UUO. Using LASSO and SAM (significance analysis of microarrays), we identified a set of well-measured metabolites that accurately predicted UUO-induced renal damage that was detectable by 12h after UUO, prior to apparent histological changes. Thus, DESI-MS could serve as a useful adjunct to histology in identifying renal damage and demonstrates early and broad changes in membrane associated lipids.

    View details for DOI 10.1038/s41598-019-47396-x

    View details for PubMedID 31358807

  • Optimization of Molecules via Deep Reinforcement Learning. Scientific reports Zhou, Z., Kearnes, S., Li, L., Zare, R. N., Riley, P. 2019; 9 (1): 10752

    Abstract

    We present a framework, which we call Molecule Deep Q-Networks (MolDQN), for molecule optimization by combining domain knowledge of chemistry and state-of-the-art reinforcement learning techniques (double Q-learning and randomized value functions). We directly define modifications on molecules, thereby ensuring 100% chemical validity. Further, we operate without pre-training on any dataset to avoid possible bias from the choice of that set. MolDQN achieves comparable or better performance against several other recently published algorithms for benchmark molecular optimization tasks. However, we also argue that many of these tasks are not representative of real optimization problems in drug discovery. Inspired by problems faced during medicinal chemistry lead optimization, we extend our model with multi-objective reinforcement learning, which maximizes drug-likeness while maintaining similarity to the original molecule. We further show the path through chemical space to achieve optimization for a molecule to understand how the model works.

    View details for DOI 10.1038/s41598-019-47148-x

    View details for PubMedID 31341196

  • Photon catalysis of deuterium iodide photodissociation PHYSICAL CHEMISTRY CHEMICAL PHYSICS Hilsabeck, K., Meiser, J. L., Sneha, M., Balakrishnan, N., Zare, R. N. 2019; 21 (26): 14195–204

    View details for DOI 10.1039/c8cp06107f

    View details for Web of Science ID 000474136100030

  • The CM carbonaceous chondrite regolith Diepenveen METEORITICS & PLANETARY SCIENCE Langbroek, M., Jenniskens, P., Kriegsman, L. M., Nieuwenhuis, H., De Kort, N., Kuiper, J., Van Westrenen, W., Zolensky, M. E., Ziegler, K., Yin, Q., Sanborn, M. E., Wimpenny, J., Yamakawa, A., De Vet, S. J., Meier, M. M., Welten, K. C., Nishiizumi, K., Caffee, M. W., Burton, A. S., Dworkin, J. P., Glavin, D. P., Wu, Q., Zare, R. N., Ruf, A., Harir, M., Schmitt-Kopplin, P., Diepenveen Meteorite Consortium 2019; 54 (7): 1431–61

    View details for DOI 10.1111/maps.13297

    View details for Web of Science ID 000478847500003

  • Micrometer-Sized Water Droplets Induce Spontaneous Reduction. Journal of the American Chemical Society Lee, J. K., Samanta, D., Nam, H. G., Zare, R. N. 2019

    Abstract

    Bulk water serves as an inert solvent for many chemical and biological reactions. Here, we report a striking exception. We observe that in micrometer-sized water droplets (microdroplets), spontaneous reduction of several organic molecules occurs, pyruvate to lactate, lipoic acid to dihydrolipoic acid, fumarate to succinate, and oxaloacetate to malate. This reduction proceeds in microdroplets without any added electron donors or acceptors and without any applied voltage. In three of the four cases, the reduction efficiency is 90% or greater when the concentration of the dissolved organic species is less than 0.1 muM. None of these reactions occurs spontaneously in bulk water. One example demonstrating the possible broad application of reduction in water microdroplets to organic molecules is the reduction of acetophenone to form 1-phenylethanol. Taken together, these results show that microdroplets provide a new foundation for green chemistry by rendering water molecules to be highly electrochemically active without any added reducing agent or applied potential. In this manner, aqueous microdroplets might have provided a route for abiotic reduction reactions in the prebiotic era, thereby providing organic molecules with a reducing power before the advent of biotic reducing machineries.

    View details for DOI 10.1021/jacs.9b03227

    View details for PubMedID 31244167

  • HD (v=1, j=2, m) orientation controls HD-He rotationally inelastic scattering near 1 K JOURNAL OF CHEMICAL PHYSICS Perreault, W. E., Mukherjee, N., Zare, R. N. 2019; 150 (17)

    View details for DOI 10.1063/1.5096531

    View details for Web of Science ID 000467255500025

  • Mechanistic Study of Ruthenium-Catalyzed C-H Hydroxylation Reveals an Unexpected Pathway for Catalyst Arrest. Journal of the American Chemical Society Mack, J. B., Walker, K. L., Robinson, S. G., Zare, R. N., Sigman, M. S., Waymouth, R. M., Du Bois, J. 2019

    Abstract

    We have recently disclosed [(dtbpy)2RuCl2] as an effective precatalyst for chemoselective C-H hydroxylation of C(sp3)-H bonds and have noted a marked disparity in reaction performance between 4,4'-di- tert-butyl-2,2'-bipyridine (dtbpy)- and 2,2'-bipyridine (bpy)-derived complexes. A desire to understand the origin of this difference and to further advance this catalytic method has motivated the comprehensive mechanistic investigation described herein. Details of this reaction have been unveiled through evaluation of ligand structure-activity relationships, electrochemical and kinetic studies, and pressurized sample infusion high-resolution mass spectrometry (PSI-MS). Salient findings from this investigation include the identification of more than one active oxidant and three disparate mechanisms for catalyst decomposition/arrest. Catalyst efficiency, as measured by turnover number, has a strong inverse correlation with the rate and extent of ligand dissociation, which is dependent on the identity of bipyridyl 4,4'-substituent groups. Dissociated bipyridyl ligand is oxidized to mono- and bis- N-oxide species under the reaction conditions, the former of which is found to act as a potent catalyst poison, yielding a catalytically inactive tris-ligated [Ru(dtbpy)2(dtbpy N-oxide)]2+ complex. Insights gained through this work highlight the power of PSI-MS for studies of complex reaction processes and are guiding ongoing efforts to develop high-performance, next-generation catalyst systems for C-H hydroxylation.

    View details for PubMedID 30601662

  • HD (v = 1, j = 2, m) orientation controls HD-He rotationally inelastic scattering near 1 K. The Journal of chemical physics Perreault, W. E., Mukherjee, N., Zare, R. N. 2019; 150 (17): 174301

    Abstract

    To investigate how molecular orientations affect low energy scattering, we have studied the rotational relaxation of HD (v = 1, j = 2, m) → (v' = 1, j' = 0) by collision with ground-state He, where v, j, and m designate the vibrational, rotational, and magnetic quantum numbers, respectively. We experimentally probed different collision geometries by preparing three specific m sublevels, including an m entangled sublevel, belonging to a single rovibrational (v = 1, j = 2) energy level within the ground electronic state of HD using Stark-induced adiabatic Raman passage. Low collision energies (0-5 K) were achieved by coexpanding a 1:19 HD:He mixture in a highly collimated supersonic beam, which has defined the direction of the collision velocity and restricted the incoming orbital angular momentum states, defined by the quantum number l, to l ≤ 2. Partial wave analysis of experimental data shows that a single l = 2 input orbital dominates the scattered angular distribution, implying the presence of a collisional resonance. The differential scattering angular distribution exhibits a greater than fourfold stereodynamic preference for the m = 0 input state vs m = ±2, when the quantization axis is oriented parallel to the collision velocity.

    View details for PubMedID 31067864

  • Absolute Quantitation of Oxidizable Peptides by Coulometric Mass Spectrometry. Journal of the American Society for Mass Spectrometry Zhao, P., Zare, R. N., Chen, H. 2019

    Abstract

    Quantitation methods for peptides using mass spectrometry have advanced rapidly. These methods rely on using standard and/or isotope-labeled peptides, which might be difficult or expensive to synthesize. To tackle this challenge, we present a new approach for absolute quantitation without the use of standards or calibration curves based on coulometry combined with mass spectrometry (MS). In this approach, which we call coulometric mass spectrometry (CMS), the mass spectrum of a target peptide containing one or more tyrosine residues is recorded before and after undergoing electrochemical oxidation. We record the total integrated oxidation current from the electrochemical measurement, which according to the Faraday's Law of coulometry, provides the number of moles of oxidized peptide. The ion intensity ratio of the target peptide before and after oxidation provides an excellent estimate of the fraction of the peptide that has been oxidized, from which the total amount of peptide is calculated. The striking strength of CMS is that it needs no standard peptide, but CMS does require the peptide to contain a known number of oxidizable groups. To illustrate the power of this method, we analyzed various tyrosine-containing peptides such as GGYR, DRVY, oxytocin, [Arg8]-vasotocin and angiotensinogen 1-14 with a quantification error ranging from - 7.5 to + 2.4%. This approach is also applicable to quantifying phosphopeptides and could be useful in proteomics research.

    View details for DOI 10.1007/s13361-019-02299-z

    View details for PubMedID 31429055

  • Stark-induced adiabatic Raman passage examined through the preparation of D2 (v = 2, j = 0) and D2 (v = 2, j = 2, m = 0). The Journal of chemical physics Perreault, W. E., Mukherjee, N., Zare, R. N. 2019; 150 (23): 234201

    Abstract

    We study the conditions that must be met for successful preparation of a large ensemble in a specific target quantum state using Stark-induced adiabatic Raman passage (SARP). In particular, we show that the threshold condition depends on the relative magnitudes of the Raman polarizability (r0v) and the difference of the optical polarizabilities (Δα00→vj) of the initial (v = 0, j = 0) and the target (v, j) rovibrational levels. Here, v and j are the vibrational and rotational quantum numbers, respectively. To illustrate how the operation of SARP is controlled by these two parameters, we experimentally prepared D2 (v = 2, j = 0) and D2 (v = 2, j = 2, m = 0) in a beam of D2 (v = 0, j = 0) molecules using a sequence of partially overlapping pump and Stokes laser pulses. By comparing theory and experiment, we were able to determine the Raman polarizability r02 ≈ 0.3 × 10-41 Cm/(V/m) and the difference polarizabilities Δα00→20 ≈ 1.4 × 10-41 Cm/(V/m) and Δα00→22 ≈ 3.4 × 10-41 Cm/(V/m) for the two Raman transitions. Our experimental data and theoretical calculations show that because the ratio r/Δα is larger for the (0,0) → (2,0) transition than the (0,0) → (2,2) transition, much less optical power is required to transfer a large population to the (v = 2, j = 0) level. Nonetheless, our experiment demonstrates that substantial population transfer to both the D2 (v = 2, j = 0) and D2 (v = 2, j = 2, m = 0) is achieved using appropriate laser fluences. Our derived threshold condition demonstrates that with increasing vibrational quantum number, it becomes more difficult to achieve large amounts of population transfer.

    View details for DOI 10.1063/1.5109261

    View details for PubMedID 31228886

  • 1,4-Benzoquinone antimicrobial agents against Staphylococcus aureus and Mycobacterium tuberculosis derived from scorpion venom. Proceedings of the National Academy of Sciences of the United States of America Carcamo-Noriega, E. N., Sathyamoorthi, S., Banerjee, S., Gnanamani, E., Mendoza-Trujillo, M., Mata-Espinosa, D., Hernández-Pando, R., Veytia-Bucheli, J. I., Possani, L. D., Zare, R. N. 2019

    Abstract

    Two 1,4-benzoquinone derivatives, found in the venom of the scorpion Diplocentrus melici following exposure to air, have been isolated, characterized, synthesized, and assessed for antimicrobial activities. Initially a white, viscous liquid, the extracted venom colors within minutes under ambient conditions. From this colored mixture, two compounds, one red, the other blue, were isolated and purified using chromatography. After a variety of NMR and mass spectrometry experiments, the red compound was determined to be 3,5- dimethoxy-2-(methylthio)cyclohexa-2,5-diene-1,4-dione, and the blue compound was determined to be 5-methoxy-2,3- bis(methylthio)cyclohexa-2,5-diene-1,4-dione. Because extremely small amounts of these compounds were isolated from the scorpion venom, we developed laboratory syntheses from commercially available precursors, allowing us to produce sufficient quantities for crystallization and biological assays. The red benzoquinone is effective against Staphylococcus aureus [minimum inhibitory concentration (MIC) = 4 µg/mL], while the blue benzoquinone is active against Mycobacterium tuberculosis (MIC = 4 µg/mL) and even against a multidrug-resistant (MDR) strain with nearly equal effectiveness. The bactericidal effects of both benzoquinones show comparable activity to commercially available antibiotics used against these pathogens and were cytotoxic to neoplastic cell lines, suggesting their potential as lead compounds for the development of novel antimicrobial and anticancer drugs. Importantly, the blue benzoquinone was also effective in vivo with mouse models of MDR tuberculosis infection. After treatment for 2 mo, four mice with late-stage active MDR tuberculosis had a significant decrease in pulmonary bacillary loads and tissue damage. Healthy mice served as negative controls and tolerated treatment well, without adverse side effects.

    View details for DOI 10.1073/pnas.1812334116

    View details for PubMedID 31182590

  • Photon catalysis of deuterium iodide photodissociation. Physical chemistry chemical physics : PCCP Hilsabeck, K. I., Meiser, J. L., Sneha, M., Balakrishnan, N., Zare, R. N. 2018

    Abstract

    A catalyst enhances a reaction pathway without itself being consumed or changed. Recently, there has been growing interest in the concept of "photon catalysis" in which nonresonant photons, which are neither absorbed nor scattered, promote reactions. The driving force behind this effect is the interaction between the strong electric field associated with a pulsed, focused laser and the polarizability of the reacting system. In this study, the effect of near-infrared, nonresonant radiation on the photodissociation of deuterium iodide is demonstrated. We use nanosecond pulses rather than time-resolved spectroscopy to investigate the average effect of the electric field on the branching ratio for forming D + I(2P3/2) and D + I(2P1/2). Changes in the measured D-atom speeds between field-free and strong-field conditions confirm substantial differences in dissociation dynamics. Both the magnitude and direction of change in the branching ratios are dependent upon the photodissociation wavelength. Experiments and theoretical calculations confirm that the mechanism for photon catalysis under these conditions is dynamic Stark shifting of potential energy surfaces rather than electric-field-induced alignment of reagent molecules.

    View details for PubMedID 30516765

  • Selective synthesis in microdroplets of 2-phenyl-2,3-dihydrophthalazine-1,4-dione from phenyl hydrazine with phthalic anhydride or phthalic acid. Chemistry (Weinheim an der Bergstrasse, Germany) Zare, R. N., Gao, D., Jin, F., Yan, X. 2018

    Abstract

    Pyridazine derivatives are privileged structures because of their potential biological and optical properties. Traditional synthesis methods usually require acid or base as a catalyst under reflux conditions with reaction times ranging from hours to a few days or require microwave assistance to induce the reaction. Herein, we present the accelerated synthesis of a pyridazine derivative, 2-phenyl-2,3-dihydrophthalazine-1,4-dione, PDHP, in electrosprayed microdroplets containing 1:1 v/v mixture of phenyl hydrazine and phthalic anhydride or phthalic acid. This reaction occurred on the submillisecond timescale with good yield (over 90% with the choice of solvent) without using an external catalyst at room temperature. In sharp contrast to the bulk reaction of obtaining a mixture of two products, the reaction in confined microdroplets yield only the important six-membered heterocyclic product PDHP. Results indicated that surface reactions in microdroplets with low pH values cause selectivity, acceleration, and high yield.

    View details for PubMedID 30417449

  • Supersonic beams of mixed gases: A method for studying cold collisions CHEMICAL PHYSICS Perreault, W. E., Mukherjee, N., Zare, R. N. 2018; 514: 150–53

    View details for DOI 10.1016/j.chemphys.2018.02.017

    View details for Web of Science ID 000448668600017

  • Combining Desorption Electrospray Ionization Mass Spectrometry Imaging and Machine Learning for Molecular Recognition of Myocardial Infarction. Analytical chemistry Margulis, K., Zhou, Z., Fang, Q., Sievers, R. E., Lee, R. J., Zare, R. N. 2018

    Abstract

    Lipid profile changes in heart muscle have been previously linked to cardiac ischemia and myocardial infarction, but the spatial distribution of lipids and metabolites in ischemic heart remains to be fully investigated. We performed desorption electrospray ionization mass spectrometry imaging of hearts from in vivo myocardial infarction mouse models. In these mice, myocardial ischemia was induced by blood supply restriction via a permanent ligation of left anterior descending coronary artery. We showed that applying the machine learning algorithm of gradient boosting tree ensemble to the ambient mass spectrometry imaging data allows us to distinguish segments of infarcted myocardium from normally perfused hearts on a pixel by pixel basis. The machine learning algorithm selected 62 molecular ion peaks important for classification of each 200 mum-diameter pixel of the cardiac tissue map as normally perfused or ischemic. This approach achieved very high average accuracy (97.4%), recall (95.8%), and precision (96.8%) at a spatial resolution of 200 mum. In addition, we determined the chemical identity of 27 species, mostly small metabolites and lipids, selected by the algorithm as the most significant for cardiac pathology classification. This molecular signature of myocardial infarction may provide new mechanistic insights into cardiac ischemia, assist with infarct size assessment, and point toward novel therapeutic interventions.

    View details for PubMedID 30188683

  • Real-time mass-spectrometric screening of droplet-scale electrochemical reactions ANALYST Zhang, H., Yu, K., Li, N., He, J., Qiao, L., Li, M., Wang, Y., Zhang, D., Jiang, J., Zare, R. N. 2018; 143 (18): 4247–50

    Abstract

    A droplet-scale, real-time electrochemical reaction screening platform based on droplet spray ionization mass spectrometry (DSI-MS) has been developed. The N,N-dimethylaniline (DMA) radical cation with a half-life of microseconds was readily detected by MS during the electrooxidation of DMA, and the subsequent reactions were followed in real time for minutes.

    View details for DOI 10.1039/c8an00957k

    View details for Web of Science ID 000444553400003

    View details for PubMedID 30027961

  • Water microdroplets catalyze chemical reactions Lee, J., Nam, H., Zare, R. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000447600002433

  • Adventures in cold chemistry Zare, R., Mukherjee, N., Perreault, W. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000447609103482

  • Reducing-agent-free and template-free synthesis of metal nanostructures in aqueous microdroplets Lee, J., Samanta, D., Nam, H., Zare, R. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000447609101400

  • An Alkaloid from Scorpion Venom: Chemical Structure and Synthesis. Journal of natural products Banerjee, S., Gnanamani, E., Lynch, S. R., Zuniga, F. Z., Jimenez-Vargas, J. M., Possani, L. D., Zare, R. N. 2018

    Abstract

    While most scorpion venom components identified in the past are peptidic or proteinic in nature, we report here a new alkaloid isolated from the venom of the Mexican scorpion Megacormus gertschi. Nuclear magnetic resonance and mass spectrometric investigations elucidate the structure of the alkaloid as ( Z)- N-(2-(1 H-imidazol-4-yl)ethyl)-3-(4-hydroxy-3-methoxyphenyl)-2-methoxyacrylamide (1). A chemical method of synthesizing this alkaloid is also described. Although abundant in venom, the above alkaloid was not found to have insecticidal activity. Structural analysis suggests that this venom alkaloid might be of potential interest for evaluating its medicinal effect.

    View details for PubMedID 30028606

  • Enhancement of reaction rate in small-sized droplets: A combined analytical and simulation study. The Journal of chemical physics Mondal, S., Acharya, S., Biswas, R., Bagchi, B., Zare, R. N. 2018; 148 (24): 244704

    Abstract

    Several recent mass spectrometry experiments reveal a marked enhancement of the reaction rate of organic reactions in microdroplets. This enhancement has been tentatively attributed to the accumulation of excess charge on a surface, which in turn can give rise to a lowering of activation energy of the reaction. Here we model the reactions in droplets as a three-step process: (i) diffusion of a reactant from the core of the droplet to the surface, (ii) search by diffusion of the reactant on the surface to find a reactive partner, and finally (iii) the intrinsic reaction leading to bond breaking and product formation. We obtain analytic expressions for the mean search time (MST) to find a target located on the surface by a reactant in both two- and three-dimensional droplets. Analytical results show quantitative agreement with Brownian dynamics simulations. We find, as also reported earlier, that the MST varies as R2/D, where R is the radius of the droplet and D is the diffusion constant of the molecules in the droplet medium. We also find that a hydronium ion in the vicinity can substantially weaken the bond and hence lowers the activation barrier. We observe a similar facilitation of bond breaking in the presence of a static dipolar electric field along any of the three Cartesian axes. If the intrinsic reaction is faster compared to the mean search time involved, it becomes primarily a diffusion-controlled process; otherwise the reaction cannot be accelerated in the droplet medium. The air-droplet interface provides a different environment compared to the interior of the droplet. Hence, we might also expect a completely different mechanism and products in the case of droplet reactions.

    View details for PubMedID 29960367

  • Preparative microdroplet synthesis of carboxylic acids from aerobic oxidation of aldehydes CHEMICAL SCIENCE Yan, X., Lai, Y., Zare, R. N. 2018; 9 (23): 5207–11

    View details for DOI 10.1039/c8sc01580e

    View details for Web of Science ID 000435350200011

  • In Situ Mass Spectrometric Screening and Studying of the Fleeting Chain Propagation of Aniline ANALYTICAL CHEMISTRY Yu, K., Zhang, H., He, J., Zare, R. N., Wang, Y., Li, L., Li, N., Zhang, D., Jiang, J. 2018; 90 (12): 7154–57

    Abstract

    A simple and effective approach to studying the mechanism of electrooxidation of aniline (ANI) is reported in this paper. It was accomplished by an innovative electrochemistry (EC)-mass spectrometry (MS) coupling, which can sample directly from a droplet-scale reacting electrolyte for mass spectrometric analysis. With this setup, the polymer chain growth of ANI could be monitored in situ and in real-time. The short-lived radical cations (ANI•+, m/ z 93.06) as well as the soluble dimer ( m/ z 183.09) and oligomers ( m/ z 274.13, 365.18, ...) were successfully captured. Using the EC-MS and tandem mass spectrometry, the dimers produced by head-to-tail (4-aminodiphenylamine), head-to-head (hydrazobenzene), and tail-to-tail (benzidine) coupling of radical cations were found in the same polymerization process. Moreover, the EC-MS method was also applicable for determining the propagation speed of ANI when applying different electrolyte salts and oxidizing potentials.

    View details for PubMedID 29873225

  • Surface characterization and free thyroid hormones response of chemically modified poly(ethylene terephthalate) blood collection tubes APPLIED SURFACE SCIENCE Dil, E., Kim, S. C., Saffar, A., Ajji, A., Zare, R. N., Sattayapiwat, A., Esguerra, V., Bowen, R. R. 2018; 442: 602–12

    View details for DOI 10.1016/j.apsusc.2018.02.177

    View details for Web of Science ID 000428294500070

  • Electrically controlled drug release using pH-sensitive polymer films. Nanoscale Neumann, S. E., Chamberlayne, C. F., Zare, R. N. 2018; 10 (21): 10087–93

    Abstract

    Drug delivery systems (DDS) that allow spatially and temporally controlled release of drugs are of particular interest in the field of drug delivery. These systems create opportunities for individually tailored doses of drugs to be administered as well as reduce side effects by localizing the initial drug dose to the organ of interest. We present an electroresponsive DDS in the form of a bioresorbable nanocomposite film which operates at low voltages (<-2 V). The method is based on electrochemically generating local pH changes at an electrode surface to induce dissolution of a pH-sensitive polymer, which is used as the carrier material. We previously demonstrated this proof-of-concept using a poly(methyl methacrylate-co-methacrylic acid) (co-PMMA) copolymer commercially marketed as Eudragit S100 (EGT). However, as EGT is soluble at a pH above 7, experiments were performed in isotonic saline solutions (pH 6.4). In this work, we have synthesized co-PMMA with a variety of monomer ratios to shift the solubility of the copolymer to higher pH values, and developed a polymer that can be used under physiologically relevant conditions. The generalizability of this system was demonstrated by showing controlled release of different drug molecules with varying parameters like size, hydrophobicity, and pKa. Fluorescein, a hydrophilic model compound, meloxicam, a hydrophobic anti-arthritic medication, curcumin, a small molecule with anti-cancer therapeutic potential, and insulin, a polypeptide hormone used in the treatment of hypoglycemia, could all be released on demand with minimal leakage. The drug loading achieved was 32 wt% by weight of the co-polymer.

    View details for PubMedID 29781009

  • Ultra-low voltage triggered release of an anticancer drug from polypyrrole nanoparticles NANOSCALE Samanta, D., Hosseini-Nassab, N., McCarty, A. D., Zare, R. N. 2018; 10 (20): 9773–79

    Abstract

    We have synthesized polypyrrole nanoparticles using three different oxidizing agents (hydrogen peroxide, chloroauric acid and ferric chloride) and shown that films assembled from these nanoparticles have significantly different drug release profiles. When ferric chloride is used as the oxidizing agent, it is possible to release drugs at voltages as low as -0.05 V, almost an order of magnitude lower than typically used voltages. These ultra-low voltage responsive nanoparticles widen the window of operation of conducting polymers and enable delivery of redox active drugs. As an example, we have shown pulsed release of the chemotherapeutic methotrexate at voltages as low as -0.075 V, demonstrating the potential application of these nanoparticles in cancer treatment. We have also verified the anti-tumor efficacy of the released drug using PC12 cell cultures.

    View details for PubMedID 29767192

  • Fluorescence Polarization Anisotropy in Microdroplets. The journal of physical chemistry letters Zhou, Z., Yan, X., Lai, Y., Zare, R. N. 2018: 2928–32

    Abstract

    Chemical reactions can be greatly accelerated in microdroplets, but the factors that lead to acceleration are still being elucidated. Using rhodamine 6G (R6G) as a model compound, we studied the density distribution and fluorescence polarization anisotropy of this dye in water-in-oil microdroplets. We found the density of R6G is higher on the surface of the microdroplets, and the ratio of the surface density to that of the center grows with increasing microdroplet radius or with decreasing R6G concentration. The measured fluorescence polarization anisotropy at the surface is almost the same for droplets of different sizes but becomes larger when the concentration is lowered. We also performed three-dimensional simulations by treating R6G+ and its associated anion as a dipole of fixed length and magnitude. The simulation results match quite well the experimental measurements, showing that the density distribution and fluorescence polarization anisotropy can be largely explained by a simple electrostatic model.

    View details for PubMedID 29763551

  • Mechanistic Analysis of the C-H Amination Reaction of Menthol by CuBr2 and Selectfluor JOURNAL OF ORGANIC CHEMISTRY Sathyamoorthi, S., Lai, Y., Bain, R. M., Zare, R. N. 2018; 83 (10): 5681–87

    Abstract

    The mechanism of the Ritter-type C-H amination reaction of menthol with acetonitrile using CuBr2, Selectfluor, and Zn(OTf)2, first disclosed by Baran and coworkers in 2012, was studied using a combination of online electrospray ionization mass spectrometry, continuous UV/vis spectrometric monitoring, and density functional theory calculations. In addition to corroborating Baran's original mechanistic proposal, these studies uncovered a second pathway to product formation, which likely only occurs in microdroplets. DFT calculations show that neither pathway has a barrier that is greater than 6.8 kcal/mol, suggesting that both mechanisms are potentially operative under ambient conditions.

    View details for PubMedID 29683651

  • Nanomaterial Preparation by Extrusion through Nanoporous Membranes SMALL Guo, P., Huang, J., Zhao, Y., Martin, C. R., Zare, R. N., Moses, M. A. 2018; 14 (18): e1703493

    Abstract

    Template synthesis represents an important class of nanofabrication methods. Herein, recent advances in nanomaterial preparation by extrusion through nanoporous membranes that preserve the template membrane without sacrificing it, which is termed as "non-sacrificing template synthesis," are reviewed. First, the types of nanoporous membranes used in nanoporous membrane extrusion applications are introduced. Next, four common nanoporous membrane extrusion strategies: vesicle extrusion, membrane emulsification, precipitation extrusion, and biological membrane extrusion, are examined. These methods have been utilized to prepare a wide range of nanomaterials, including liposomes, emulsions, nanoparticles, nanofibers, and nanotubes. The principle and historical context of each specific technology are discussed, presenting prominent examples and evaluating their positive and negative features. Finally, the current challenges and future opportunities of nanoporous membrane extrusion methods are discussed.

    View details for PubMedID 29468837

  • Cold quantum-controlled rotationally inelastic scattering of HD with H-2 and D-2 reveals collisional partner reorientation NATURE CHEMISTRY Perreault, W. E., Mukherjee, N., Zare, R. N. 2018; 10 (5): 561–67

    Abstract

    Molecular interactions are best probed by scattering experiments. Interpretation of these studies has been limited by lack of control over the quantum states of the incoming collision partners. We report here the rotationally inelastic collisions of quantum-state prepared deuterium hydride (HD) with H2 and D2 using a method that provides an improved control over the input states. HD was coexpanded with its partner in a single supersonic beam, which reduced the collision temperature to 0-5 K, and thereby restricted the involved incoming partial waves to s and p. By preparing HD with its bond axis preferentially aligned parallel and perpendicular to the relative velocity of the colliding partners, we observed that the rotational relaxation of HD depends strongly on the initial bond-axis orientation. We developed a partial-wave analysis that conclusively demonstrates that the scattering mechanism involves the exchange of internal angular momentum between the colliding partners. The striking differences between H2/HD and D2/HD scattering suggest the presence of anisotropically sensitive resonances.

    View details for PubMedID 29662208

  • Microdroplets Accelerate Ring Opening of Epoxides JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Lai, Y., Sathyamoorthi, S., Bain, R. M., Zare, R. N. 2018; 29 (5): 1036–43

    Abstract

    The nucleophilic opening of an epoxide is a classic organic reaction that has widespread utility in both academic and industrial applications. We have studied the reaction of limonene oxide with morpholine to form 1-methyl-2-morpholino-4-(prop-1-en-2-yl) cyclohexan-1-ol in bulk solution and in electrosprayed microdroplets with a 1:1 v/v water/methanol solvent system. We find that even after 90 min at room temperature, there is no product detected by nuclear magnetic resonance spectroscopy in bulk solution whereas in room-temperature microdroplets (2-3 μm in diameter), the yield is already 0.5% in a flight time of 1 ms as observed by mass spectrometry. This constitutes a rate acceleration of ~ 105 in the microdroplet environment, if we assume that as much as 5% of product is formed in bulk after 90 min of reaction time. We examine how the reaction rate depends on droplet size, solvent composition, sheath gas pressure, and applied voltage. These factors profoundly influence the extent of reaction. This dramatic acceleration is not limited to just one system. We have also found that the nucleophilic opening of cis-stilbene oxide by morpholine is similarly accelerated. Such large acceleration factors in reaction rates suggest the use of microdroplets for ring opening of epoxides in other systems, which may have practical significance if such a procedure could be scaled. Graphical Abstract This graphical image is distorted.  It is too extended in the vertical direction.  Please fix.ᅟ.

    View details for PubMedID 29569167

  • Autonomy and accountability in institutions of higher education CURRENT SCIENCE Zare, R. N. 2018; 114 (8): 1603–4

    View details for Web of Science ID 000430655100008

  • Spontaneous formation of gold nanostructures in aqueous microdroplets NATURE COMMUNICATIONS Lee, J., Samanta, D., Nam, H., Zare, R. N. 2018; 9: 1562

    Abstract

    The synthesis of gold nanostructures has received widespread attention owing to many important applications. We report the accelerated synthesis of gold nanoparticles (AuNPs), as well as the reducing-agent-free and template-free synthesis of gold nanoparticles and nanowires in aerosol microdroplets. At first, the AuNP synthesis are carried out by fusing two aqueous microdroplet streams containing chloroauric acid and sodium borohydride. The AuNPs (~7 nm in diameter) are produced within 60 µs at the rate of 0.24 nm µs-1. Compared to bulk solution, microdroplets enhance the size and the growth rate of AuNPs by factors of about 2.1 and 1.2 × 105, respectively. Later, we find that gold nanoparticles and nanowires (~7 nm wide and >2000 nm long) are also formed in microdroplets in the absence of any added reducing agent, template, or externally applied charge. Thus, water microdroplets not only accelerate the synthesis of AuNPs by orders of magnitude, but they also cause spontaneous formation of gold nanostructures.

    View details for PubMedID 29674623

  • Rotationally inelastic scattering of HD (v=1, j=2) with H2 or D2 near 1 Kelvin Perreault, W., Mukherjee, N., Zare, R. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000435539905444

  • Upgrading asphaltenes by oil droplets striking a charged TiO2-immobilized paper surface Lai, Y., Zhou, Z., Basheer, C., Zare, R. AMER CHEMICAL SOC. 2018

    View details for Web of Science ID 000435539900411

  • Spontaneous Reduction of Biomolecules on the Surface of Water Droplets Lee, J., Samanta, D., Nam, I., Nam, H., Zare, R. N. CELL PRESS. 2018: 542A

    View details for Web of Science ID 000430563200462

  • Abiotic Fabrication of Sugar Phosphates and Ribonucleosides in Water Microdroplets Nam, I., Lee, J., Name, H., Zare, R. N. CELL PRESS. 2018: 438A

    View details for Web of Science ID 000430450000685

  • Quantum interference in chemical reactions PHYSICS TODAY Javier Aoiz, F., Zare, R. N. 2018; 71 (2): 70–71

    View details for Web of Science ID 000424052800019

  • Abiotic synthesis of purine and pyrimidine ribonucleosides in aqueous microdroplets PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Nam, I., Nam, H., Zare, R. N. 2018; 115 (1): 36–40

    Abstract

    Aqueous microdroplets (<1.3 µm in diameter on average) containing 15 mM d-ribose, 15 mM phosphoric acid, and 5 mM of a nucleobase (uracil, adenine, cytosine, or hypoxanthine) are electrosprayed from a capillary at +5 kV into a mass spectrometer at room temperature and 1 atm pressure with 3 mM divalent magnesium ion (Mg2+) as a catalyst. Mass spectra show the formation of ribonucleosides that comprise a four-letter alphabet of RNA with a yield of 2.5% of uridine (U), 2.5% of adenosine (A), 0.7% of cytidine (C), and 1.7% of inosine (I) during the flight time of ∼50 µs. In the case of uridine, no catalyst is required. An aqueous solution containing guanine cannot be generated under the same conditions given the extreme insolubility of guanine in water. However, inosine can base pair with cytidine and thus substitute for guanosine. Thus, a full set of ribonucleosides to generate the purine-pyrimidine base pairs A-U and I-C are spontaneously generated in aqueous microdroplets under similar mild conditions.

    View details for PubMedID 29255025

  • Distinguishing malignant from benign microscopic skin lesions using desorption electrospray ionization mass spectrometry imaging. Proceedings of the National Academy of Sciences of the United States of America Margulis, K., Chiou, A. S., Aasi, S. Z., Tibshirani, R. J., Tang, J. Y., Zare, R. N. 2018

    Abstract

    Detection of microscopic skin lesions presents a considerable challenge in diagnosing early-stage malignancies as well as in residual tumor interrogation after surgical intervention. In this study, we established the capability of desorption electrospray ionization mass spectrometry imaging (DESI-MSI) to distinguish between micrometer-sized tumor aggregates of basal cell carcinoma (BCC), a common skin cancer, and normal human skin. We analyzed 86 human specimens collected during Mohs micrographic surgery for BCC to cross-examine spatial distributions of numerous lipids and metabolites in BCC aggregates versus adjacent skin. Statistical analysis using the least absolute shrinkage and selection operation (Lasso) was employed to categorize each 200-µm-diameter picture element (pixel) of investigated skin tissue map as BCC or normal. Lasso identified 24 molecular ion signals, which are significant for pixel classification. These ion signals included lipids observed at m/z 200-1,200 and Krebs cycle metabolites observed at m/z < 200. Based on these features, Lasso yielded an overall 94.1% diagnostic accuracy pixel by pixel of the skin map compared with histopathological evaluation. We suggest that DESI-MSI/Lasso analysis can be employed as a complementary technique for delineation of microscopic skin tumors.

    View details for PubMedID 29866838

  • Site-selective bromination of sp3 C-H bonds. Chemical science Sathyamoorthi, S., Banerjee, S., Du Bois, J., Burns, N. Z., Zare, R. N. 2018; 9 (1): 100–104

    Abstract

    A method for converting sp3 C-H to C-Br bonds using an N-methyl sulfamate directing group is described. The reaction employs Rh2(oct)4 and a mixture of NaBr and NaOCl and is performed in aqueous solution open to air. For all sulfamates examined, oxidation occurs with high selectivity at the γ-carbon, affording a uniquely predictable method for C-H bond halogenation. Results from a series of mechanistic experiments suggest that substrate oxidation likely proceeds by a radical chain process. Initial formation of an N-halogenated sulfamate followed by Rh-mediated homolysis generates an N-centered radical, which serves as the active oxidant.

    View details for PubMedID 29629078

  • Preparative microdroplet synthesis of carboxylic acids from aerobic oxidation of aldehydes. Chemical science Yan, X., Lai, Y. H., Zare, R. N. 2018; 9 (23): 5207–11

    Abstract

    Single liquid-phase and liquid-liquid phase reactions in microdroplets have shown much faster kinetics than that in the bulk phase. This work extends the scope of microdroplet reactions to gas-liquid reactions and achieves preparative synthesis. We report highly efficient aerobic oxidation of aldehydes to carboxylic acids in microdroplets. Molecular oxygen plays two roles: (1) as the sheath gas to shear the aldehyde solution into microdroplets, and (2) as the sole oxidant. The dramatic increase of the surface-area-to-volume ratio of microdroplets compared to bulk solution, and the efficient mixing of gas and liquid phases using spray nozzles allow effective mass transfer between aldehydes and molecular oxygen. The addition of catalytic nickel(ii) acetate is shown to accelerate further microdroplet reactions of this kind. We show that aliphatic, aromatic, and heterocyclic aldehydes can be oxidized to the corresponding carboxylic acids in a mixture of water and ethanol using the nickel(ii) acetate catalyst, in moderate to excellent yields (62-91%). The microdroplet synthesis is scaled up to make it preparative. For example, aerobic oxidation of 4-tert-butylbenzaldehyde to 4-tert-butylbenzoic acid was achieved at a rate of 10.5 mg min-1 with an isolated product yield of 66%.

    View details for PubMedID 29997875

  • Nonresonant photons catalyze photodissociation of phenol. Journal of the American Chemical Society Hilsabeck, K. I., Meiser, J. L., Sneha, M., Harrison, J. A., Zare, R. N. 2018

    Abstract

    Phenol represents an ideal polyatomic system for demonstrating photon catalysis because of its large polarizability, well-characterized excited-state potential energy surfaces, and nonadiabatic dissociation dynamics. A nonresonant IR pulse (1064 nm) supplies a strong electric field (εo = 4 x 107 V/cm) during the photolysis of isolated phenol (C6H5OH) molecules to yield C6H5O + H near two known energetic thresholds: the S1/S2 conical intersection and the S1 - S0 origin. H-atom speed distributions show marked changes in the relative contributions of dissociative pathways in both cases, compared to the absence of the nonresonant IR pulse. Results indicate that nonresonant photons lower the activation barrier for some pathways relative to others by dynamically Stark shifting the excited-state potential energy surfaces rather than aligning molecules in the strong electric field. Theoretical calculations offer support for the experimental interpretation.

    View details for PubMedID 30571915

  • Site-selective bromination of sp3 C–H bonds Chem.Sci Sathyamoorthi, S., Banerjee, S., Du Bois, J., Burns, N. Z., Zare, R. N. 2018; 9: 100-104

    Abstract

    A method for converting sp3 C-H to C-Br bonds using an N-methyl sulfamate directing group is described. The reaction employs Rh2(oct)4 and a mixture of NaBr and NaOCl and is performed in aqueous solution open to air. For all sulfamates examined, oxidation occurs with high selectivity at the γ-carbon, affording a uniquely predictable method for C-H bond halogenation. Results from a series of mechanistic experiments suggest that substrate oxidation likely proceeds by a radical chain process. Initial formation of an N-halogenated sulfamate followed by Rh-mediated homolysis generates an N-centered radical, which serves as the active oxidant.

    View details for DOI 10.1039/C7SC04611A

    View details for PubMedCentralID PMC5873043

  • Optimizing Chemical Reactions with Deep Reinforcement Learning ACS CENTRAL SCIENCE Zhou, Z., Li, X., Zare, R. N. 2017; 3 (12): 1337–44

    Abstract

    Deep reinforcement learning was employed to optimize chemical reactions. Our model iteratively records the results of a chemical reaction and chooses new experimental conditions to improve the reaction outcome. This model outperformed a state-of-the-art blackbox optimization algorithm by using 71% fewer steps on both simulations and real reactions. Furthermore, we introduced an efficient exploration strategy by drawing the reaction conditions from certain probability distributions, which resulted in an improvement on regret from 0.062 to 0.039 compared with a deterministic policy. Combining the efficient exploration policy with accelerated microdroplet reactions, optimal reaction conditions were determined in 30 min for the four reactions considered, and a better understanding of the factors that control microdroplet reactions was reached. Moreover, our model showed a better performance after training on reactions with similar or even dissimilar underlying mechanisms, which demonstrates its learning ability.

    View details for PubMedID 29296675

    View details for PubMedCentralID PMC5746857

  • "On-Droplet" Chemistry: The Cycloaddition of Diethyl Azodicarboxylate and Quadricyclane ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Bain, R. M., Sathyamoorthi, S., Zare, R. N. 2017; 56 (47): 15083–87

    Abstract

    Sharpless and co-workers previously studied the [2σ+2σ+2π] cycloaddition of diethyl azodicarboxylate (DEAD) and quadricyclane and reported that the addition of water to the neat reagents caused an acceleration in the reaction rate, giving birth to what has been called "on-water" chemistry. We have examined the same reaction in aqueous microdroplets (ca. 5 μm diameter) and find that the cycloaddition reaction is accelerated even further (by a factor of 102 ) compared to that of the "on-water" reaction reported previously. The trends of acceleration in solvents other than water demonstrated by Sharpless and colleagues were replicated in the corresponding microdroplet experiments. We also find that DEAD reacts with itself to form a variety of hydrazine carboxylates and intercept intermediates of this reaction in microdroplets to validate a mechanism proposed herein. We suggest that "on-droplet" chemistry, similar to "on-water" chemistry, may be a general process of synthetic interest.

    View details for PubMedID 28992393

  • On-demand electrically controlled drug release from resorbable nanocomposite films NANOSCALE Samanta, D., Mehrotra, R., Margulis, K., Zare, R. N. 2017; 9 (42): 16429–36

    Abstract

    Electroresponsive materials are promising carriers for developing drug delivery systems (DDSs) with excellent spatial, temporal, and dosage control over drug release. Current electroresponsive systems use high voltages (2-25 V), are not bioresorbable, or use materials with unknown long-term biocompatibility. We report here a nanocomposite film that is resorbable, electroresponsive at low voltages (<-2 V), and composed of entirely FDA-approved materials. Our DDS is based on poly(methyl methacrylate-co-methacrylic acid), commercially marketed as Eudragit S100 (EGT), which has pH-dependent aqueous solubility. Nanometric films of drug-loaded EGT were designed, synthesized, and coated with a protective layer of chitosan. We hypothesized that electric stimuli would cause local pH changes on the working electrode, leading to pH-responsive dissolution of EGT with concomitant drug release. Our results confirm that local pH changes impart electroresponsive release behavior to the films. Furthermore, drug release scales linearly with voltage, current, and time. The generalizability of the system is shown through the release of several molecules of varying hydrophobicity, pKa, and size, including fluorescein (free acid and sodium salt), curcumin, meloxicam, and glucagon. The ability to modulate drug release with the applied stimulus can be utilized to design minimally invasive drug delivery devices based on bioresorbable electronics. Such devices would allow for personalized medicine in the treatment of chronic diseases.

    View details for PubMedID 29058737

  • Formation of Polymeric Nanocubes by Self-Assembly and Crystallization of Dithiolane-Containing Triblock Copolymers. Angewandte Chemie (International ed. in English) Margulis, K., Zhang, X., Joubert, L., Bruening, K., Tassone, C. J., Zare, R. N., Waymouth, R. M. 2017

    Abstract

    Template-free fabrication of non-spherical polymeric nanoparticles is desirable for various applications, but has had limited success owing to thermodynamic favorability of sphere formation. Herein we present a simple way to prepare cubic nanoparticles of block copolymers by self-assembly from aqueous solutions at room temperature. Nanocubes with edges of 40-200 nm are formed spontaneously on different surfaces upon water evaporation from micellar solutions of triblock copolymers containing a central poly(ethylene oxide) block and terminal trimethylene carbonate/dithiolane blocks. These polymers self-assemble into 28±5 nm micelles in water. Upon drying, micelle aggregation and a kinetically controlled crystallization of central blocks evidently induce solid cubic particle formation. An approach for preserving the structures of these cubes in water by thiol- or photo-induced crosslinking was developed. The ability to solubilize a model hydrophobic drug, curcumin, was also explored.

    View details for PubMedID 29080292

  • Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Walker, K. L., Dornan, L. M., Zare, R. N., Waymouth, R. M., Mudoon, M. J. 2017; 139 (36): 12495–503

    Abstract

    Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.

    View details for PubMedID 28849921

  • Ionic and Neutral Mechanisms for C-H Bond Silylation of Aromatic Heterocycles Catalyzed by Potassium tert-Butoxide. Journal of the American Chemical Society Banerjee, S., Yang, Y., Jenkins, I. D., Liang, Y., Toutov, A. A., Liu, W., Schuman, D. P., Grubbs, R. H., Stoltz, B. M., Krenske, E. H., Houk, K. N., Zare, R. N. 2017; 139 (20): 6880-6887

    Abstract

    Exploiting C-H bond activation is difficult, although some success has been achieved using precious metal catalysts. Recently, it was reported that C-H bonds in aromatic heterocycles were converted to C-Si bonds by reaction with hydrosilanes under the catalytic action of potassium tert-butoxide alone. The use of Earth-abundant potassium cation as a catalyst for C-H bond functionalization seems to be without precedent, and no mechanism for the process was established. Using ambient ionization mass spectrometry, we are able to identify crucial ionic intermediates present during the C-H silylation reaction. We propose a plausible catalytic cycle, which involves a pentacoordinate silicon intermediate consisting of silane reagent, substrate, and the tert-butoxide catalyst. Heterolysis of the Si-H bond, deprotonation of the heteroarene, addition of the heteroarene carbanion to the silyl ether, and dissociation of tert-butoxide from silicon lead to the silylated heteroarene product. The steps of the silylation mechanism may follow either an ionic route involving K(+) and (t)BuO(-) ions or a neutral heterolytic route involving the [KO(t)Bu]4 tetramer. Both mechanisms are consistent with the ionic intermediates detected experimentally. We also present reasons why KO(t)Bu is an active catalyst whereas sodium tert-butoxide and lithium tert-butoxide are not, and we explain the relative reactivities of different (hetero)arenes in the silylation reaction. The unique role of KO(t)Bu is traced, in part, to the stabilization of crucial intermediates through cation-π interactions.

    View details for DOI 10.1021/jacs.6b13032

    View details for PubMedID 28462580

  • Rapid Hydrogen-Deuterium Exchange in Liquid Droplets. Journal of the American Chemical Society Jansson, E. T., Lai, Y., Santiago, J. G., Zare, R. N. 2017; 139 (20): 6851-6854

    Abstract

    The rate of hydrogen-deuterium exchange (HDX) in aqueous droplets of phenethylamine has been determined with submillisecond temporal resolution by mass spectrometry using nanoelectrospray ionization with a theta-capillary. The average speed of the microdroplets is measured using microparticle image velocimetry. The droplet travel time is varied from 20 to 320 μs by changing the distance between the emitter and the heated inlet to the mass spectrometer and the voltage applied to the emitter source. The droplets were found to accelerate by ∼30% during their observable travel time. Our droplet imaging shows that the theta-capillary produces two Taylor cone-jets (one per channel), causing mixing to take place from droplet fusion in the Taylor spray zone. Phenethylamine (ϕCH2CH2NH2) was chosen to study because it has only one functional group (-NH2) that undergoes rapid HDX. We model the HDX with a system of ordinary differential equations. The rate constant for the formation of -NH2D(+) from -NH3(+) is 3660 ± 290 s(-1), and the rate constant for the formation of -NHD2(+) from -NH2D(+) is 3330 ± 270 s(-1). The observed rates are about 3 times faster than what has been reported for rapidly exchangeable peptide side-chain groups in bulk measurements using stopped-flow kinetics and NMR spectroscopy. We also applied this technique to determine the HDX rates for a small 10-residue peptide, angiotensin I, in aqueous droplets, from which we found a 7-fold acceleration of HDX in the droplet compared to that in bulk solution.

    View details for DOI 10.1021/jacs.7b03541

    View details for PubMedID 28481522

  • Potassium tert-Butoxide-Catalyzed Dehydrogenative C-H Silylation of Heteroaromatics: A Combined Experimental and Computational Mechanistic Study. Journal of the American Chemical Society Liu, W., Schuman, D. P., Yang, Y., Toutov, A. A., Liang, Y., Klare, H. F., Nesnas, N., Oestreich, M., Blackmond, D. G., Virgil, S. C., Banerjee, S., Zare, R. N., Grubbs, R. H., Houk, K. N., Stoltz, B. M. 2017; 139 (20): 6867-6879

    Abstract

    We recently reported a new method for the direct dehydrogenative C-H silylation of heteroaromatics utilizing Earth-abundant potassium tert-butoxide. Herein we report a systematic experimental and computational mechanistic investigation of this transformation. Our experimental results are consistent with a radical chain mechanism. A trialkylsilyl radical may be initially generated by homolytic cleavage of a weakened Si-H bond of a hypercoordinated silicon species as detected by IR, or by traces of oxygen which can generate a reactive peroxide by reaction with [KOt-Bu]4 as indicated by density functional theory (DFT) calculations. Radical clock and kinetic isotope experiments support a mechanism in which the C-Si bond is formed through silyl radical addition to the heterocycle followed by subsequent β-hydrogen scission. DFT calculations reveal a reasonable energy profile for a radical mechanism and support the experimentally observed regioselectivity. The silylation reaction is shown to be reversible, with an equilibrium favoring products due to the generation of H2 gas. In situ NMR experiments with deuterated substrates show that H2 is formed by a cross-dehydrogenative mechanism. The stereochemical course at the silicon center was investigated utilizing a (2)H-labeled silolane probe; complete scrambling at the silicon center was observed, consistent with a number of possible radical intermediates or hypercoordinate silicates.

    View details for DOI 10.1021/jacs.6b13031

    View details for PubMedID 28403611

  • Can all bulk-phase reactions be accelerated in microdroplets? ANALYST Banerjee, S., Gnanamani, E., Yan, X., Zare, R. N. 2017; 142 (9): 1399-1402

    Abstract

    Recent studies have shown that microdroplet reactions are markedly accelerated compared to the corresponding bulk-phase reactions. This raises the question whether all reactions can be sped up by this means. We present a counter example, and we show that the reaction mechanism in microdroplets can differ sharply from that in bulk, especially because of the distinct microdroplet surface environment. This analysis helps to guide us how to choose and control reactions in microdroplets and provides a possible perspective on utilizing microdroplet chemistry to scale up synthesis.

    View details for DOI 10.1039/c6an02225a

    View details for PubMedID 28332662

  • Oncogene KRAS activates fatty acid synthase, resulting in specific ERK and lipid signatures associated with lung adenocarcinoma PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Gouw, A. M., Eberlin, L. S., Margulis, K., Sullivan, D. K., Toal, G. G., Tong, L., Zare, R. N., Felsher, D. W. 2017; 114 (17): 4300-4305

    Abstract

    KRAS gene mutation causes lung adenocarcinoma. KRAS activation has been associated with altered glucose and glutamine metabolism. Here, we show that KRAS activates lipogenesis, and this activation results in distinct proteomic and lipid signatures. By gene expression analysis, KRAS is shown to be associated with a lipogenesis gene signature and specific induction of fatty acid synthase (FASN). Through desorption electrospray ionization MS imaging (DESI-MSI), specific changes in lipogenesis and specific lipids are identified. By the nanoimmunoassay (NIA), KRAS is found to activate the protein ERK2, whereas ERK1 activation is found in non-KRAS-associated human lung tumors. The inhibition of FASN by cerulenin, a small molecule antibiotic, blocked cellular proliferation of KRAS-associated lung cancer cells. Hence, KRAS is associated with activation of ERK2, induction of FASN, and promotion of lipogenesis. FASN may be a unique target for KRAS-associated lung adenocarcinoma remediation.

    View details for DOI 10.1073/pnas.1617709114

    View details for PubMedID 28400509

  • Diagnosis of prostate cancer by desorption electrospray ionization mass spectrometric imaging of small metabolites and lipids PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Banerjee, S., Zare, R. N., Tibshirani, R. J., Kunder, C. A., Nolley, R., Fan, R., Brooks, J. D., Sonn, G. A. 2017; 114 (13): 3334-3339

    Abstract

    Accurate identification of prostate cancer in frozen sections at the time of surgery can be challenging, limiting the surgeon's ability to best determine resection margins during prostatectomy. We performed desorption electrospray ionization mass spectrometry imaging (DESI-MSI) on 54 banked human cancerous and normal prostate tissue specimens to investigate the spatial distribution of a wide variety of small metabolites, carbohydrates, and lipids. In contrast to several previous studies, our method included Krebs cycle intermediates (m/z <200), which we found to be highly informative in distinguishing cancer from benign tissue. Malignant prostate cells showed marked metabolic derangements compared with their benign counterparts. Using the "Least absolute shrinkage and selection operator" (Lasso), we analyzed all metabolites from the DESI-MS data and identified parsimonious sets of metabolic profiles for distinguishing between cancer and normal tissue. In an independent set of samples, we could use these models to classify prostate cancer from benign specimens with nearly 90% accuracy per patient. Based on previous work in prostate cancer showing that glucose levels are high while citrate is low, we found that measurement of the glucose/citrate ion signal ratio accurately predicted cancer when this ratio exceeds 1.0 and normal prostate when the ratio is less than 0.5. After brief tissue preparation, the glucose/citrate ratio can be recorded on a tissue sample in 1 min or less, which is in sharp contrast to the 20 min or more required by histopathological examination of frozen tissue specimens.

    View details for DOI 10.1073/pnas.1700677114

    View details for Web of Science ID 000397607300049

    View details for PubMedID 28292895

    View details for PubMedCentralID PMC5380053

  • Two New Devices for Identifying Electrochemical Reaction Intermediates with Desorption Electrospray Ionization Mass Spectrometry. Analytical chemistry Cheng, H., Yan, X., Zare, R. N. 2017; 89 (5): 3191-3198

    Abstract

    Desorption electrospray ionization mass spectrometry (DESI-MS) previously has been used to capture and identify transient intermediates in electrochemical redox reactions on a platinum-covered rotating waterwheel. We present here two different setups that use a flat surface with porous carbon tape as the working electrode, where analyte-containing microdroplets from the DESI probe contacted with electrolyte supplied onto the surface. One setup had the conducting carbon tape in the form of a grooved inclined plane; the other one was in the form of a flat plane that had the conducting carbon tape as its front surface. Both these setups, which were relatively robust and easy to operate, overcame interference from the electrospray sheath gas that disturbs and dries the flowing electrolyte. By using the inclined-plane device, we observed radical cations and dimer species generated in the electrochemical oxidation of triphenylamine, diimine and imine alcohol in the electrochemical oxidation of uric acid, and the reductive cleavage of disulfide bonds in glutathione disulfide. By using the device with the flat carbon tape, we detected nitrenium ions generated in the electrochemical oxidation of N,N'-dimethyoxydiphenylamine and di-p-tolylamine. Our experience suggests that the flat porous carbon tape surface might be preferable over the inclined plane because of its ease of setup.

    View details for DOI 10.1021/acs.analchem.6b05124

    View details for PubMedID 28193008

  • Two-Phase Reactions in Microdroplets without the Use of Phase-Transfer Catalysts. Angewandte Chemie (International ed. in English) Yan, X., Cheng, H., Zare, R. N. 2017

    Abstract

    Many important chemical transformations occur in two-phase reactions, which are widely used in chemical, pharmaceutical, and polymer manufacturing. We present an efficient method for performing two-phase reactions in microdroplets sheared by sheath gas without using a phase-transfer catalyst. This avoids disadvantages such as thermal instability, high cost, and, especially, the need to separate and recycle the catalysts. We show that various alcohols can be oxidized to the corresponding aldehydes and ketones within milliseconds in moderate to good yields (50-75 %). The scale-up of the present method was achieved at an isolated rate of 1.2 mg min(-1) for the synthesis of 4-nitrobenzylaldehyde from 4-nitrobenzyl alcohol in the presence of sodium hypochlorite. The biphasic nature of this process, which avoids use of a phase-transfer catalyst, greatly enhances synthetic effectiveness.

    View details for DOI 10.1002/anie.201612308

    View details for PubMedID 28225181

  • Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation QUARTERLY REVIEWS OF BIOPHYSICS Lee, J. K., Nam, H. G., Zare, R. N. 2017; 50: 1-7

    Abstract

    Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 µM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 µm diameter; 84 ± 18 m s-1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets.

    View details for DOI 10.1017/S0033583517000014

    View details for Web of Science ID 000396422700001

    View details for PubMedCentralID PMC5729759

  • Personal Information from Latent Fingerprints Using Desorption Electrospray Ionization Mass Spectrometry and Machine Learning ANALYTICAL CHEMISTRY Zhou, Z., Zare, R. N. 2017; 89 (2): 1369-1372

    Abstract

    Desorption electrospray ionization-mass spectrometry imaging (DESI-MSI) was applied to latent fingerprints to obtain not only spatial patterns but also chemical maps. Samples with similar lipid compositions as those of the fingerprints were collected by swiping a glass slide across the forehead of consenting adults. A machine learning model called gradient boosting tree ensemble (GDBT) was applied to the samples that allowed us to distinguish between different genders, ethnicities, and ages (within 10 years). The results from 194 samples showed accuracies of 89.2%, 82.4%, and 84.3%, respectively. Specific chemical species that were determined by the feature selection of GDBT were identified by tandem mass spectrometry. As a proof-of-concept, the machine learning model trained on the sample data was applied to overlaid latent fingerprints from different individuals, giving accurate gender and ethnicity information from those fingerprints. The results suggest that DESI-MSI imaging of fingerprints with GDBT analysis might offer a significant advance in forensic science.

    View details for DOI 10.1021/acs.analchem.6b04498

    View details for Web of Science ID 000392458100047

    View details for PubMedID 28194988

  • Electrically controlled release of insulin using polypyrrole nanoparticles NANOSCALE Hosseini-Nassab, N., Samanta, D., Abdolazimi, Y., Annes, J. P., Zare, R. N. 2017; 9 (1): 143-149

    Abstract

    Conducting polymers present an opportunity for developing programmable, adjustable, spatially, and temporally controllable drug delivery systems. While several small molecule drugs have been released from thin conductive polymeric films successfully, delivering large molecule therapeutics, such as polypeptides and nucleic acids, has remained a significant challenge. Poor drug loading (∼ng cm(-2)) of thin films coupled with film instability has, in many cases, made conducting polymer films refractory to clinical development. To address these limitations, we have utilized conductive polymer nanoparticulate backbones to controllably release insulin, a high molecular weight, clinically relevant polypeptide. We find that the interaction between insulin and the polymer scaffold can be described by a simple Langmuir-type adsorption model. By modifying the ratio of the amount of nanoparticles to the amount of insulin, we have obtained drug loading percentages estimated to be as high as 51 wt% percent. In vivo experiments in mice confirmed retained bioactivity of the released insulin after electrical stimulation.

    View details for DOI 10.1039/c6nr08288b

    View details for Web of Science ID 000391739300020

    View details for PubMedID 27929180

    View details for PubMedCentralID PMC5215613

  • Polymer-spray mass spectrometric detection and quantitation of hydrophilic compounds and some narcotics. Rapid communications in mass spectrometry : RCM Dulay, M. T., Zare, R. N. 2017; 31 (19): 1651–58

    Abstract

    High-throughput screening of biofluids is essential in monitoring concentration of a variety of drugs to determine their efficacy and toxicity. Organosiloxane polymers prepared by sol-gel chemistry as sample supports, and electrospray ionization emitters in a single material and as an alternative to paper substrates, is described in this study.Hydrophobic drugs and hydrophilic streptomycin were analyzed by polymer-spray mass spectrometry with an LTQ-Orbitrap mass spectrometer. Drug samples in urine (1-2 μL) were deposited on an OSX polymer, allowed to dry, then electrosprayed from the polymer tip into the mass spectrometer without sample pretreatment. The OSX polymers, whose polarity and porosity can be controlled, were prepared by sol-gel chemistry where methyl-substituted alkoxysilanes were hydrolyzed in the presence of a pore template and an acid catalyst.Five nanograms each of seven narcotic drugs were detected in <1 min (relative standard deviation (RSD) of response <1% for each drug). Calibration curves of cocaine and streptomycin in urine were used to establish the performance of the polymer. For sample 1 (n = 2), the mean recovery for cocaine was 81% with paper and 90% with polymer. Streptomycin is detected with polymer, not with paper; for samples 1 and 2 (n = 3), mean recovery was 97% and 95%, respectively.Organosiloxane polymers achieve more sensitive analysis than paper, allowing for more accurate quantitation of both hydrophobic and hydrophilic drug compounds. The ability to tailor the polymer polarity and porosity allows for the synthesis of a wide range of polymers, and thus opens many possibilities for further development and applications.

    View details for PubMedID 28792093

  • Quantum control of molecular collisions at 1 kelvin. Science (New York, N.Y.) Perreault, W. E., Mukherjee, N., Zare, R. N. 2017; 358 (6361): 356–59

    Abstract

    Measurement of vector correlations in molecular scattering is an indispensable tool for mapping out interaction potentials. In a coexpanded supersonic beam, we have studied the rotationally inelastic process wherein deuterium hydride (HD) (v = 1, j = 2) collides with molecular deuterium (D2) to form HD (v = 1, j = 1), where v and j are the vibrational and rotational quantum numbers, respectively. HD (v = 1, j = 2) was prepared by Stark-induced adiabatic Raman passage, with its bond axis aligned preferentially parallel or perpendicular to the lab-fixed relative velocity. The coexpansion brought the collision temperature down to 1 kelvin, restricting scattering to s and p partial waves. Scattering angular distributions showed a dramatic stereodynamic preference (~3:1) for perpendicular versus parallel alignment. The four-vector correlation measured between the initial and final velocities and the initial and final rotational angular momentum vectors of HD provides insight into the strong anisotropic forces present in the collision process.

    View details for PubMedID 29051378

  • Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation. Quarterly reviews of biophysics Lee, J. K., Nam, H. G., Zare, R. N. 2017; 50: e2

    Abstract

    Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 µM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 µm diameter; 84 ± 18 m s-1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets.

    View details for PubMedID 29233214

  • Mechanistic analysis of a copper-catalyzed C-H oxidative cyclization of carboxylic acids. Chemical science Banerjee, S., Sathyamoorthi, S., Du Bois, J., Zare, R. N. 2017; 8 (10): 7003–8

    Abstract

    We recently reported that carboxylic acids can be oxidized to lactone products by potassium persulfate and catalytic copper acetate. Here, we unravel the mechanism for this C-H functionalization reaction using desorption electrospray ionization, online electrospray ionization, and tandem mass spectrometry. Our findings suggest that electron transfer from a transient benzylic radical intermediate reduces Cu(ii) to Cu(i), which is then re-oxidized to Cu(ii) in the catalytic cycle. The resulting benzylic carbocation is trapped by the pendant carboxylate group to give the lactone product. Formation of the putative benzylic carbocation is supported by Hammett analysis. The proposed mechanism for this copper-catalyzed oxidative cyclization process differs from earlier reports of analogous reactions, which posit a substrate carboxylate radical as the reactive oxidant.

    View details for PubMedID 29147527

    View details for PubMedCentralID PMC5642147

  • Abiotic production of sugar phosphates and uridine ribonucleoside in aqueous microdroplets. Proceedings of the National Academy of Sciences of the United States of America Nam, I., Lee, J. K., Nam, H. G., Zare, R. N. 2017; 114 (47): 12396–400

    Abstract

    Phosphorylation is an essential chemical reaction for life. This reaction generates fundamental cell components, including building blocks for RNA and DNA, phospholipids for cell walls, and adenosine triphosphate (ATP) for energy storage. However, phosphorylation reactions are thermodynamically unfavorable in solution. Consequently, a long-standing question in prebiotic chemistry is how abiotic phosphorylation occurs in biological compounds. We find that the phosphorylation of various sugars to form sugar-1-phosphates can proceed spontaneously in aqueous microdroplets containing a simple mixture of sugars and phosphoric acid. The yield for d-ribose-1-phosphate reached over 6% at room temperature, giving a ΔGvalue of -1.1 kcal/mol, much lower than the +5.4 kcal/mol for the reaction in bulk solution. The temperature dependence of the product yield for the phosphorylation in microdroplets revealed a negative enthalpy change (ΔH= -0.9 kcal/mol) and a negligible change of entropy (ΔS= 0.0007 kcal/mol·K). Thus, the spontaneous phosphorylation reaction in microdroplets occurred by overcoming the entropic hurdle of the reaction encountered in bulk solution. Moreover, uridine, a pyrimidine ribonucleoside, is generated in aqueous microdroplets containing d-ribose, phosphoric acid, and uracil, which suggests the possibility that microdroplets could serve as a prebiotic synthetic pathway for ribonucleosides.

    View details for PubMedID 29078402

    View details for PubMedCentralID PMC5703324

  • Preparation of a selected high vibrational energy level of isolated molecules. journal of chemical physics Perreault, W. E., Mukherjee, N., Zare, R. N. 2016; 145 (15): 154203-?

    Abstract

    Stark induced adiabatic Raman passage (SARP) allows us to prepare an appreciable concentration of isolated molecules in a specific, high-lying vibrational level. The process has general applicability, and, as a demonstration, we transfer nearly 100 percent of the HD (v = 0, J = 0) in a supersonically expanded molecular beam of HD molecules to HD (v = 4, J = 0). This is achieved with a sequence of partially overlapping nanosecond pump (355 nm) and Stokes (680 nm) single-mode laser pulses of unequal intensities. By comparing our experimental data with our theoretical calculations, we are able to draw two important conclusions: (1) using SARP a large population (>10(10) molecules per laser pulse) is prepared in the (v = 4, J = 0) level of HD and (2) the polarizability α00,40 (≅0.6 × 10(-41) C m(2) V(-1)) for the (v = 0, J = 0) to (v = 4, J = 0) Raman overtone transition is only about five times smaller than α00,10 for the (v = 0, J = 0) to (v = 1, J = 0) fundamental Raman transition. Moreover, the SARP process selects a specific rotational level in the vibrational manifold and can prepare one or a phased linear combination of magnetic sublevels (M states) within the selected vibrational-rotational level. This capability of preparing selected, highly excited vibrational levels of molecules under collision-free conditions opens new opportunities for fundamental scattering experiments.

    View details for PubMedID 27782486

  • A Study of Heterogeneous Catalysis by Nanoparticle-Embedded Paper-Spray Ionization Mass Spectrometry. Angewandte Chemie (International ed. in English) Banerjee, S., Basheer, C., Zare, R. N. 2016; 55 (41): 12807-12811

    Abstract

    We have developed nanoparticle-embedded paper-spray mass spectrometry for studying three types of heterogeneously catalyzed reactions: 1) Palladium-nanoparticle-catalyzed Suzuki cross-coupling reactions, 2) palladium- or silver-nanoparticle-catalyzed 4-nitrophenol reduction, and 3) gold-nanoparticle-catalyzed glucose oxidation. These reactions were almost instantaneous on the nanocatalyst-embedded paper, which subsequently transferred the transient intermediates and products to a mass spectrometer for their detection. This in situ method of capturing transient intermediates and products from heterogeneous catalysis is highly promising for investigating the mechanism of catalysis and rapidly screening catalytic activity under ambient conditions.

    View details for DOI 10.1002/anie.201607204

    View details for PubMedID 27633445

  • Impact of Laboratory-Induced Thermal Maturity on Asphaltene Molecular Structure ENERGY & FUELS Pomerantz, A. E., Doan, T. V., Craddock, P. R., Bake, K. D., Kleinberg, R. L., Burnham, A. K., Wu, Q., Zare, R. N., Brodnik, G., Lo, W. C., Grayson, M., Mitra-Kirtley, S., Bolin, T. B., Wu, T. 2016; 30 (9): 7025-7036

    View details for DOI 10.1021/acs.energyfuels.6b01238

    View details for Web of Science ID 000383641000017

  • Catalytic Carbonylative Spirolactonization of Hydroxycyclopropanols. Journal of the American Chemical Society Davis, D. C., Walker, K. L., Hu, C., Zare, R. N., Waymouth, R. M., Dai, M. 2016; 138 (33): 10693-10699

    Abstract

    A palladium-catalyzed cascade carbonylative spirolactonization of hydroxycyclopropanols has been developed to efficiently synthesize oxaspirolactones common to many complex natural products of important therapeutic value. The mild reaction conditions, high atom economy, broad substrate scope, and scalability of this new method were highlighted in expedient total syntheses of the Turkish tobacco natural products α-levantanolide and α-levantenolide in two and four steps, respectively. The hydroxycyclopropanol substrates are readily available in one step via a Kulinkovich reaction of the corresponding lactones. Mechanistic studies utilizing high-resolution electrospray ionization mass spectrometry (ESI-MS) identified several key intermediates in the catalytic cycle, as well as those related to catalyst decomposition and competitive pathways.

    View details for DOI 10.1021/jacs.6b06573

    View details for PubMedID 27459274

  • Direct Copper(III) Formation from O2 and Copper(I) with Histamine Ligation. Journal of the American Chemical Society Gary, J. B., Citek, C., Brown, T. A., Zare, R. N., Wasinger, E. C., Stack, T. D. 2016; 138 (31): 9986-9995

    Abstract

    Histamine chelation of copper(I) by a terminal histidine residue in copper hydroxylating enzymes activates dioxygen to form unknown oxidants, generally assumed as copper(II) species. The direct formation of copper(III)-containing products from the oxygenation of histamine-ligated copper(I) complexes is demonstrated here, indicating that copper(III) is a viable oxidation state in such products from both kinetic and thermodynamic perspectives. At low temperatures, both trinuclear Cu(II)2Cu(III)O2 and dinuclear Cu(III)2O2 predominate, with the distribution dependent on the histamine ligand structure and oxygenation conditions. Kinetics studies suggest the bifurcation point to these two products is an unobserved peroxide-level dimer intermediate. The hydrogen atom reactivity difference between the trinuclear and binuclear complexes at parity of histamine ligand is striking. This behavior is best attributed to the accessibility of the bridging oxide ligands to exogenous substrates rather than a difference in oxidizing abilities of the clusters.

    View details for DOI 10.1021/jacs.6b05538

    View details for PubMedID 27467215

  • Miniaturized Linear Wire Ion Trap Mass Analyzer ANALYTICAL CHEMISTRY Wu, Q., Li, A., Tian, Y., Zare, R. N., Austin, D. E. 2016; 88 (15): 7800-7806

    Abstract

    We report a linear ion trap (LIT) in which the electric field is formed by fine wires held under tension and accurately positioned using holes drilled in two end plates made of plastic. The coordinates of the hole positions were optimized in simulation. The stability diagram and mass spectra using boundary ejection were compared between simulation and experiment and good agreement was found. The mass spectra from experiments show peak widths (fwhm) in units of mass-to-charge of around 0.38 Th using a scan rate of 3830 Th/s. The limits of detection are 137 ppbv and 401 ppbv for benzene and toluene, respectively. Different sizes of the wire ion trap can be easily fabricated by drilling holes in scaled positions. Other distinguishing features, such as high ion and photon transmission, low capacitance, high tolerance to mechanical and assembly error, and low weight, are discussed.

    View details for DOI 10.1021/acs.analchem.6b01830

    View details for PubMedID 27373557

  • Scaffold-mediated BMP-2 minicircle DNA delivery accelerated bone repair in a mouse critical-size calvarial defect model JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A Keeney, M., Chung, M. T., Zielins, E. R., Paik, K. J., McArdle, A., Morrison, S. D., Ransom, R. C., Barbhaiya, N., Atashroo, D., Jacobson, G., Zare, R. N., Longaker, M. T., Wan, D. C., Yang, F. 2016; 104 (8): 2099-2107

    Abstract

    Scaffold-mediated gene delivery holds great promise for tissue regeneration. However, previous attempts to induce bone regeneration using scaffold-mediated non-viral gene delivery rarely resulted in satisfactory healing. We report a novel platform with sustained release of minicircle DNA (MC) from PLGA scaffolds to accelerate bone repair. MC was encapsulated inside PLGA scaffolds using supercritical CO2 , which showed prolonged release of MC. Skull-derived osteoblasts transfected with BMP-2 MC in vitro result in higher osteocalcin gene expression and mineralized bone formation. When implanted in a critical-size mouse calvarial defect, scaffolds containing luciferase MC lead to robust in situ protein production up to at least 60 days. Scaffold-mediated BMP-2 MC delivery leads to substantially accelerated bone repair as early as two weeks, which continues to progress over 12 weeks. This platform represents an efficient, long-term nonviral gene delivery system, and may be applicable for enhancing repair of a broad range of tissues types. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2099-2107, 2016.

    View details for DOI 10.1002/jbm.a.35735

    View details for Web of Science ID 000379736500025

    View details for PubMedID 27059085

  • Pancreatic Cancer Surgical Resection Margins: Molecular Assessment by Mass Spectrometry Imaging. PLoS medicine Eberlin, L. S., Margulis, K., Planell-Mendez, I., Zare, R. N., Tibshirani, R., Longacre, T. A., Jalali, M., Norton, J. A., Poultsides, G. A. 2016; 13 (8)

    Abstract

    Surgical resection with microscopically negative margins remains the main curative option for pancreatic cancer; however, in practice intraoperative delineation of resection margins is challenging. Ambient mass spectrometry imaging has emerged as a powerful technique for chemical imaging and real-time diagnosis of tissue samples. We applied an approach combining desorption electrospray ionization mass spectrometry imaging (DESI-MSI) with the least absolute shrinkage and selection operator (Lasso) statistical method to diagnose pancreatic tissue sections and prospectively evaluate surgical resection margins from pancreatic cancer surgery.Our methodology was developed and tested using 63 banked pancreatic cancer samples and 65 samples (tumor and specimen margins) collected prospectively during 32 pancreatectomies from February 27, 2013, to January 16, 2015. In total, mass spectra for 254,235 individual pixels were evaluated. When cross-validation was employed in the training set of samples, 98.1% agreement with histopathology was obtained. Using an independent set of samples, 98.6% agreement was achieved. We used a statistical approach to evaluate 177,727 mass spectra from samples with complex, mixed histology, achieving an agreement of 81%. The developed method showed agreement with frozen section evaluation of specimen margins in 24 of 32 surgical cases prospectively evaluated. In the remaining eight patients, margins were found to be positive by DESI-MSI/Lasso, but negative by frozen section analysis. The median overall survival after resection was only 10 mo for these eight patients as opposed to 26 mo for patients with negative margins by both techniques. This observation suggests that our method (as opposed to the standard method to date) was able to detect tumor involvement at the margin in patients who developed early recurrence. Nonetheless, a larger cohort of samples is needed to validate the findings described in this study. Careful evaluation of the long-term benefits to patients of the use of DESI-MSI for surgical margin evaluation is also needed to determine its value in clinical practice.Our findings provide evidence that the molecular information obtained by DESI-MSI/Lasso from pancreatic tissue samples has the potential to transform the evaluation of surgical specimens. With further development, we believe the described methodology could be routinely used for intraoperative surgical margin assessment of pancreatic cancer.

    View details for DOI 10.1371/journal.pmed.1002108

    View details for PubMedID 27575375

  • Multiple scattering mechanisms causing interference effects in the differential cross sections of H + D2 ? HD(v' = 4, ?j') + D at 3.26 eV collision energy. journal of chemical physics Sneha, M., Gao, H., Zare, R. N., Jambrina, P. G., Menéndez, M., Aoiz, F. J. 2016; 145 (2): 024308-?

    Abstract

    Differential cross sections (DCSs) for the H + D2 → HD(v' = 4,  j') + D reaction at 3.26 eV collision energy have been measured using the photoloc technique, and the results have been compared with those from quantum and quasiclassical scattering calculations. The quantum mechanical DCSs are in good overall agreement with the experimental measurements. In common with previous results at 1.97 eV, clear interference patterns which appear as fingerlike structures have been found at 3.26 eV but in this case for vibrational states as high as v' = 4. The oscillatory structure is prominent for low rotational states and progressively disappears as j' increases. A detailed analysis, similar to that carried out at 1.97 eV, shows that the origin of these structures could be traced to interferences between well defined classical mechanisms. In addition, at this energy, we do not observe the anomalous positive j'-θ trend found for the v' = 4 manifold at lower collision energies, thus reinforcing our explanation that the anomalous distribution for HD(v' = 4,  j') at 1.97 eV only takes place for those states associated with low product recoil energies.

    View details for DOI 10.1063/1.4955294

    View details for PubMedID 27421406

  • Monitoring Enzymatic Reactions in Real Time Using Venturi Easy Ambient Sonic-Spray Ionization Mass Spectrometry ANALYTICAL CHEMISTRY Jansson, E. T., Dulay, M. T., Zare, R. N. 2016; 88 (12): 6195-6198

    Abstract

    We developed a technique to monitor spatially confined surface reactions with mass spectrometry under ambient conditions, without the need for voltage or organic solvents. Fused-silica capillaries immersed in an aqueous solution, positioned in close proximity to each other and the functionalized surface, created a laminar flow junction with a resulting reaction volume of ∼5 pL. The setup was operated with a syringe pump, delivering reagents to the surface through a fused-silica capillary. The other fused-silica capillary was connected to a Venturi easy ambient sonic-spray ionization source, sampling the resulting analytes at a slightly higher flow rate compared to the feeding capillary. The combined effects of the inflow and outflow maintains a chemical microenvironment, where the rate of advective transport overcomes diffusion. We show proof-of-concept where acetylcholinesterase was immobilized on an organosiloxane polymer through electrostatic interactions. The hydrolysis of acetylcholine by acetylcholinesterase into choline was monitored in real-time for a range of acetylcholine concentrations, fused-silica capillary geometries, and operating flow rates. Higher reaction rates and conversion yields were observed with increasing acetylcholine concentrations, as would be expected.

    View details for DOI 10.1021/acs.analchem.6b01246

    View details for Web of Science ID 000378470200019

    View details for PubMedID 27249533

    View details for PubMedCentralID PMC4917919

  • Angular and internal state distributions of H-2(+) generated by (2+1) resonance enhanced multiphoton ionization of H-2 using time-of-flight mass spectrometry JOURNAL OF CHEMICAL PHYSICS Perreault, W. E., Mukherjee, N., Zare, R. N. 2016; 144 (21)

    Abstract

    We report direct measurement of the anisotropy parameter β for the angular distribution of the photoelectron and photoion in (2 + 1) resonance enhanced multiphoton ionization process of H2 X (1)Σg (+) (v = 0, J = 0) molecules through the intermediate H2 E,F (1)Σg (+) (v' = 0, J' = 0) level (λ = 201.684 nm) using a time-of-flight mass spectrometer. The time-of-flight spectra were recorded as the direction of polarization of the ionizing laser was varied with respect to the flight axis of the H2 molecular beam and were fitted to an angular distribution in an appropriately rotated coordinate system with the z-axis oriented along the time-of-flight axis. The anisotropy parameter β was found to be 1.72 ± 0.13 by fitting the time-of-flight spectra and agreed with previous measurements. Using secondary ionization with a delayed laser pulse of different wavelength, we also determined the vibrational energy distribution of the ions, showing that 98% ± 4% of the ions are generated in their ground vibrational state, in agreement with the calculated Franck-Condon factors between the H2 E,F (1)Σg (+) (v' = 0) and H2 (+) X (1)Σg (+) (v″) vibrational levels.

    View details for DOI 10.1063/1.4952759

    View details for Web of Science ID 000378923500013

    View details for PubMedID 27276949

  • High-Resolution Live-Cell Imaging and Analysis by Laser Desorption/Ionization Droplet Delivery Mass Spectrometry ANALYTICAL CHEMISTRY Lee, J. K., Jansson, E. T., Nam, H. G., Zare, R. N. 2016; 88 (10): 5453-5461

    Abstract

    We have developed a new ambient-ionization mass spectrometric technique named laser desorption/ionization droplet delivery mass spectrometry (LDIDD-MS). LDIDD-MS permitted high-resolution, high-sensitivity imaging of tissue samples as well as measurement of both single-cell apoptosis and live-cell exocytosis. A pulsed (15 Hz) UV laser beam (266 nm) was focused on a surface covered with target analytes to trigger their desorption and ionization. A spray of liquid droplets was simultaneously directed onto the laser-focused surface region to capture the ionized analytes and deliver them to a mass spectrometer. The approach of rapid and effective capturing molecules after laser desorption/ionization allowed the limit of detection for the amino acid lysine to be as low as 2 amol under ambient ionization conditions. Two-dimensional maps of the desorbed/ionized species were recorded by moving the sample on an XY translational stage. The spatial resolution for imaging with LDIDD-MS was determined to be 2.4 µm for an ink-printed pattern and 3 µm for mouse brain tissue. We applied LDIDD-MS to single-cell analysis of apoptotic HEK cells. Differences were observed in the profiles of fatty acids and lipids between healthy HEK cells and those undergoing apoptosis: We observed the upregulation of phosphatidylcholine (PC) with a relatively shorter carbon chain length and downregulation of PC with a relatively longer carbon chain length. We also applied LDIDD-MS for a real-time direct measurement of live-cell exocytosis. The catecholamine dopamine and trace amines (phenethylamine and tyramine) were detected from live PC12 cells without damaging them.

    View details for DOI 10.1021/acs.analchem.6b00881

    View details for Web of Science ID 000376223500059

    View details for PubMedID 27110027

  • Nanotip Ambient Ionization Mass Spectrometry ANALYTICAL CHEMISTRY Zhou, Z., Lee, J. K., Kim, S. C., Zare, R. N. 2016; 88 (10): 5542-5548

    Abstract

    A method called nanotip ambient ionization mass spectrometry (NAIMS) is described, which applies high voltage between a tungsten nanotip and a metal plate to generate a plasma in which ionized analytes on the surface of the metal plate are directed to the inlet and analyzed by a mass spectrometer. The dependence of signal intensity is investigated as a function of the tip-to-plate distance, the tip size, the voltage applied at the tip, and the current. These parameters are separately optimized to achieve sensitivity or high spatial resolution. A partially observable Markov decision process is used to achieve a stabilized plasma as well as high ionization efficiency. As a proof of concept, the NAIMS technique has been applied to phenanthrene and caffeine samples for which the limits of detection were determined to be 0.14 fmol for phenanthrene and 4 amol for caffeine and to a printed caffeine pattern for which a spatial resolution of 8 ± 2 μm, and the best resolution of 5 μm, was demonstrated. The limitations of NAIMS are also discussed.

    View details for DOI 10.1021/acs.analchem.6b01212

    View details for Web of Science ID 000376223500071

    View details for PubMedID 27087600

  • Molecular Dynamics Simulation of beta-Lactoglobulin at Different Oil/Water Interfaces BIOMACROMOLECULES Zare, D., Allison, J. R., McGrath, K. M. 2016; 17 (5): 1572-1581

    Abstract

    Controlling and manipulating protein behavior at an interface is of immense relevance to a broad range of physicochemical and biological phenomena and technological processes. Although many experimental studies have contributed to rapid progress in the fundamental knowledge of protein behavior at interfaces, detailed molecular-level understanding of the mechanism of protein adsorption at an interface is still remarkably lacking. In this study, atomistic molecular dynamics simulations were used to characterize the adsorption of β-lactoglobulin at two different oil/water (O/W) interfaces, where the oil was either the marginally hydrophilic octanol or the more hydrophilic triolein, and the results were compared to those of a previous study utilizing the hydrophobic oil decane. Both the approach to the surface and the mechanism of adsorption depend upon the hydrophilicity of the oil and the interfacial tension of the O/W interface, with the nature of the adsorption, the accompanying structural changes, and the energetic driving force differing markedly between the different oils. Intriguingly, the behavior of the protein resembles that predicted for a soft spherical particle at an O/W interface. The results are also in agreement with key experimental findings, particularly the observation that proteins undergo more conformational change upon adsorption to hydrophobic surfaces, flattening out to expose hydrophobic interior residues to the surface, and that a thicker layer of native-like adsorbed protein forms at hydrophilic surfaces, and reveal structural and mechanistic detail behind each mechanism of adsorption.

    View details for DOI 10.1021/acs.biomac.5b01709

    View details for Web of Science ID 000375886500003

    View details for PubMedID 27075297

  • Better Practices in Scientific Publishing. Angewandte Chemie (International ed. in English) Zare, R. N. 2016; 55 (8): 2606–7

    View details for PubMedID 26799244

  • Performance of chemically modified plastic blood collection tubes CLINICAL BIOCHEMISTRY Bowen, R. A., Kim, S. C., Sattayapiwat, A., Austria-Esguerra, V., Zare, R. N. 2016; 49 (1-2): 90-99

    Abstract

    The objective of this study was to compare newly-modified and aged chemoPET tubes, which contain no problematic surfactants, with commercially available serum blood collection tubes (BCTs) for use in analysis of cortisol, total triiodothyronine (TT3), total thyroxine (TT4), and routine clinical chemistry analytes in serum from apparently healthy volunteers and pooled quality control (QC) specimens.Blood specimens collected from 60 apparently healthy volunteers (18 males, 42 females) and pooled QC specimens poured into seven different BCTs were analyzed by a trained phlebotomist. Cortisol, TT3, and TT4 levels were measured on an Immulite 1000 instrument and routine chemistry tests were analyzed on a Siemens RxL instrument. The significance of differences between chemoPET and other BCT types compared to glass tubes were assessed by Student's paired t-test or repeated measures ANOVA or their non-parametric equivalents. The BCT-related biases (deviation from glass tubes) in analyte concentrations were compared with the current desirable allowable bias, derived from biological variation. Serum analyte concentrations in the different BCTs that exceeded their respective significant change limits were considered clinically significant.No statistically and/or clinically significant differences were noted in the analyte concentrations from serum specimens and pooled QC material when our newly modified and aged chemoPET tubes were compared to glass and other BCTs.The chemoPET tubes described here may be a suitable alternative to serum BCTs that contain problematic surfactants known to interfere with some clinical assays on the Immulite 1000 and RxL instruments.

    View details for DOI 10.1016/j.clinbiochem.2015.09.003

    View details for Web of Science ID 000368752700017

  • Observation of electrochemically generated nitrenium ions by desorption electrospray ionization mass spectrometry. Chemical science Brown, T. A., Hosseini-Nassab, N., Chen, H., Zare, R. N. 2016; 7 (1): 329–32

    Abstract

    We report the observation of the electrochemically generated nitrenium ions of 4,4'-dimethyoxydiphenylamine and di-p-tolylamine in solution by mass spectrometry. This setup takes inspiration from desorption electrospray ionization mass spectrometry to sample directly from the surface of a rotating waterwheel working electrode for mass spectrometric analysis. Detection of the 4,4'-dimethyoxydiphenylamine nitrenium ion was expected based upon para-methoxy resonance stabilization, whereas observation of the di-p-tolylamine nitrenium ion might be unexpected because resonance stabilization from the para-substituted position is unavailable. However, the short timescale analysis of the setup allows for the isolation of the di-p-tolylamine nitrenium ion, which is electrogenerated in solution and detected mass spectrometrically.

    View details for PubMedID 28791096

  • Electroresponsive nanoparticles for drug delivery on demand NANOSCALE Samanta, D., Hosseini-Nassab, N., Zare, R. N. 2016; 8 (17): 9310-9317

    Abstract

    The potential of electroresponsive conducting polymer nanoparticles to be used as general drug delivery systems that allow electrically pulsed, linearly scalable, and on demand release of incorporated drugs is demonstrated. As examples, facile release from polypyrrole nanoparticles is shown for fluorescein, a highly water-soluble model compound, piroxicam, a lipophilic small molecule drug, and insulin, a large hydrophilic peptide hormone. The drug loading is about 13 wt% and release is accomplished in a few seconds by applying a weak constant current or voltage. To identify the parameters that should be finely tuned to tailor the carrier system for the release of the therapeutic molecule of interest, a systematic study of the factors that affect drug delivery is performed, using fluorescein as a model compound. The parameters studied include current, time, voltage, pH, temperature, particle concentration, and ionic strength. Results indicate that there are several degrees of freedom that can be optimized for efficient drug delivery. The ability to modulate linearly drug release from conducting polymers with the applied stimulus can be utilized to design programmable and minimally invasive drug delivery devices.

    View details for DOI 10.1039/c6nr01884j

    View details for Web of Science ID 000375285800029

    View details for PubMedID 27088543

  • Performance of chemically modified plastic blood collection tubes. Clinical biochemistry Bowen, R. A., Kim, S. C., Sattayapiwat, A., Austria-Esguerra, V., Zare, R. N. 2016; 49 (1): 90-99

    Abstract

    The objective of this study was to compare newly-modified and aged chemoPET tubes, which contain no problematic surfactants, with commercially available serum blood collection tubes (BCTs) for use in analysis of cortisol, total triiodothyronine (TT3), total thyroxine (TT4), and routine clinical chemistry analytes in serum from apparently healthy volunteers and pooled quality control (QC) specimens.Blood specimens collected from 60 apparently healthy volunteers (18 males, 42 females) and pooled QC specimens poured into seven different BCTs were analyzed by a trained phlebotomist. Cortisol, TT3, and TT4 levels were measured on an Immulite 1000 instrument and routine chemistry tests were analyzed on a Siemens RxL instrument. The significance of differences between chemoPET and other BCT types compared to glass tubes were assessed by Student's paired t-test or repeated measures ANOVA or their non-parametric equivalents. The BCT-related biases (deviation from glass tubes) in analyte concentrations were compared with the current desirable allowable bias, derived from biological variation. Serum analyte concentrations in the different BCTs that exceeded their respective significant change limits were considered clinically significant.No statistically and/or clinically significant differences were noted in the analyte concentrations from serum specimens and pooled QC material when our newly modified and aged chemoPET tubes were compared to glass and other BCTs.The chemoPET tubes described here may be a suitable alternative to serum BCTs that contain problematic surfactants known to interfere with some clinical assays on the Immulite 1000 and RxL instruments.

    View details for DOI 10.1016/j.clinbiochem.2015.09.003

    View details for PubMedID 26375014

  • Observation of electrochemically generated nitrenium ions by desorption electrospray ionization mass spectrometry CHEMICAL SCIENCE Brown, T. A., Hosseini-Nassab, N., Chen, H., Zare, R. N. 2016; 7 (1): 329-332

    Abstract

    We report the observation of the electrochemically generated nitrenium ions of 4,4'-dimethyoxydiphenylamine and di-p-tolylamine in solution by mass spectrometry. This setup takes inspiration from desorption electrospray ionization mass spectrometry to sample directly from the surface of a rotating waterwheel working electrode for mass spectrometric analysis. Detection of the 4,4'-dimethyoxydiphenylamine nitrenium ion was expected based upon para-methoxy resonance stabilization, whereas observation of the di-p-tolylamine nitrenium ion might be unexpected because resonance stabilization from the para-substituted position is unavailable. However, the short timescale analysis of the setup allows for the isolation of the di-p-tolylamine nitrenium ion, which is electrogenerated in solution and detected mass spectrometrically.

    View details for DOI 10.1039/c5sc02939b

    View details for Web of Science ID 000366826900037

    View details for PubMedCentralID PMC5518571

  • Going beyond electrospray: mass spectrometric studies of chemical reactions in and on liquids CHEMICAL SCIENCE Ingram, A. J., Boeser, C. L., Zare, R. N. 2016; 7 (1): 39-55

    View details for DOI 10.1039/c5sc02740c

    View details for Web of Science ID 000366826900002

  • Effects of reagent rotation on interferences in the product angular distributions of chemical reactions CHEMICAL SCIENCE Jambrina, P. G., Aldegunde, J., Aoiz, F. J., Sneha, M., Zare, R. N. 2016; 7 (1): 642-649

    View details for DOI 10.1039/c5sc03373j

    View details for Web of Science ID 000366826900076

  • Going beyond electrospray: mass spectrometric studies of chemical reactions in and on liquids. Chemical science Ingram, A. J., Boeser, C. L., Zare, R. N. 2016; 7 (1): 39–55

    Abstract

    There has been a burst in the number and variety of available ionization techniques to use mass spectrometry to monitor chemical reactions in and on liquids. Chemists have gained the capability to access chemistry at unprecedented timescales, and monitor reactions and detect intermediates under almost any set of conditions. Herein, recently developed ionization techniques that facilitate mechanistic studies of chemical processes are reviewed. This is followed by a discussion of our perspective on the judicious application of these and similar techniques in order to study reaction mechanisms.

    View details for PubMedID 28757996

  • Differential Cross Sections for the H + D-2 -> HD(v '=3, j '=4-10) + D Reaction above the Conical Intersection JOURNAL OF PHYSICAL CHEMISTRY A Gao, H., Sneha, M., Bouakline, F., Althorpe, S. C., Zare, R. N. 2015; 119 (50): 12036-12042

    View details for DOI 10.1021/acs.jpca.5b04573

    View details for PubMedID 26090780

  • Protein Analysis by Ambient Ionization Mass Spectrometry Using Trypsin-Immobilized Organosiloxane Polymer Surfaces ANALYTICAL CHEMISTRY Dulay, M. T., Eberlin, L. S., Zare, R. N. 2015; 87 (24): 12324-12330

    View details for DOI 10.1021/acs.analchem.5b03669

    View details for PubMedID 26567450

  • Syntheses of Isoquinoline and Substituted Quinolines in Charged Microdroplets. Angewandte Chemie (International ed. in English) Banerjee, S., Zare, R. N. 2015; 54 (49): 14795-14799

    Abstract

    A Pomeranz-Fritsch synthesis of isoquinoline and Friedländer and Combes syntheses of substituted quinolines were conducted in charged microdroplets produced by an electrospray process at ambient temperature and atmospheric pressure. In the bulk phase, all of these reactions are known to take a long time ranging from several minutes to a few days and to require very high acid concentrations. In sharp contrast, the present report provides clear evidence that all of these reactions occur on the millisecond timescale in the charged microdroplets without the addition of any external acid. Decreasing the droplet size and increasing the charge of the droplet both strongly contribute to reaction rate acceleration, suggesting that the reaction occurs in a confined environment on the charged surface of the droplet.

    View details for DOI 10.1002/anie.201507805

    View details for PubMedID 26450661

  • Syntheses of Isoquinoline and Substituted Quinolines in Charged Microdroplets ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Banerjee, S., Zare, R. N. 2015; 54 (49): 14795-14799

    Abstract

    A Pomeranz-Fritsch synthesis of isoquinoline and Friedländer and Combes syntheses of substituted quinolines were conducted in charged microdroplets produced by an electrospray process at ambient temperature and atmospheric pressure. In the bulk phase, all of these reactions are known to take a long time ranging from several minutes to a few days and to require very high acid concentrations. In sharp contrast, the present report provides clear evidence that all of these reactions occur on the millisecond timescale in the charged microdroplets without the addition of any external acid. Decreasing the droplet size and increasing the charge of the droplet both strongly contribute to reaction rate acceleration, suggesting that the reaction occurs in a confined environment on the charged surface of the droplet.

    View details for DOI 10.1002/anie.201507805

    View details for Web of Science ID 000367723400033

  • Mechanistic Insights into Two-Phase Radical C-H Arylations. ACS central science Baxter, R. D., Liang, Y., Hong, X., Brown, T. A., Zare, R. N., Houk, K. N., Baran, P. S., Blackmond, D. G. 2015; 1 (8): 456-462

    Abstract

    Kinetic, spectroscopic, and computational studies of radical C-H arylations highlight the interplay between chemical and physical rate processes in these multiphase reactions. Anomalous concentration dependences observed here may be reconciled by considering the role of phase transfer processes that mediate concentrations in each phase. In addition, understanding interactions through phase boundaries enables their use in optimization of reaction performance.

    View details for PubMedID 26640819

  • Mechanistic Insights into Two-Phase Radical C-H Arylations ACS CENTRAL SCIENCE Baxter, R. D., Liang, Y., Hong, X., Brown, T. A., Zare, R. N., Houk, K. N., Baran, P. S., Blackmond, D. G. 2015; 1 (8): 456-462

    Abstract

    Kinetic, spectroscopic, and computational studies of radical C-H arylations highlight the interplay between chemical and physical rate processes in these multiphase reactions. Anomalous concentration dependences observed here may be reconciled by considering the role of phase transfer processes that mediate concentrations in each phase. In addition, understanding interactions through phase boundaries enables their use in optimization of reaction performance.

    View details for DOI 10.1021/acscentsci.5b00332

    View details for Web of Science ID 000365969600011

    View details for PubMedCentralID PMC4665085

  • Imaging of Proteins in Tissue Samples Using Nanospray Desorption Electrospray Ionization Mass Spectrometry ANALYTICAL CHEMISTRY Hsu, C., Chou, P., Zare, R. N. 2015; 87 (22): 11171-11175

    View details for DOI 10.1021/acs.analchem.5b03389

    View details for PubMedID 26509582

  • Acceleration of reaction in charged microdroplets QUARTERLY REVIEWS OF BIOPHYSICS Lee, J. K., Banerjee, S., Nam, H. G., Zare, R. N. 2015; 48 (4): 437-444

    Abstract

    Using high-resolution mass spectrometry, we have studied the synthesis of isoquinoline in a charged electrospray droplet and the complexation between cytochrome c and maltose in a fused droplet to investigate the feasibility of droplets to drive reactions (both covalent and noncovalent interactions) at a faster rate than that observed in conventional bulk solution. In both the cases we found marked acceleration of reaction, by a factor of a million or more in the former and a factor of a thousand or more in the latter. We believe that carrying out reactions in microdroplets (about 1-15 μm in diameter corresponding to 0·5 pl - 2 nl) is a general method for increasing reaction rates. The mechanism is not presently established but droplet evaporation and droplet confinement of reagents appear to be two important factors among others. In the case of fused water droplets, evaporation has been shown to be almost negligible during the flight time from where droplet fusion occurs and the droplets enter the heated capillary inlet of the mass spectrometer. This suggests that (1) evaporation is not responsible for the acceleration process in aqueous droplet fusion and (2) the droplet-air interface may play a significant role in accelerating the reaction. We argue that this 'microdroplet chemistry' could be a remarkable alternative to accelerate slow and difficult reactions, and in conjunction with mass spectrometry, it may provide a new arena to study chemical and biochemical reactions in a confined environment.

    View details for DOI 10.1017/S0033583515000086

    View details for Web of Science ID 000364764300008

    View details for PubMedID 26537403

  • Catalytic Role of Multinuclear Palladium-Oxygen Intermediates in Aerobic Oxidation Followed by Hydrogen Peroxide Disproportionation JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Ingram, A. J., Walker, K. L., Zare, R. N., Waymouth, R. M. 2015; 137 (42): 13632-13646

    Abstract

    Aerobic oxidation of alcohols are catalyzed by the Pd-acetate compound [LPd(OAc)]2(OTf)2 (L = neocuproine = 2,9-dimethyl-1,10-phenanthroline) to form ketones and the release of hydrogen peroxide, but the latter rapidly undergoes disproportionation. We employ a series of kinetic and isotope labeling studies made largely possible by electrospray ionization mass spectrometry to determine the role of intermediates in causing this complex chemical transformation. The data suggested that multiple catalytic paths for H2O2 disproportionation occur, which involve formation and consumption of multinuclear Pd species. We find that the trinuclear compound [(LPd)3(μ(3)-O)2](2+), which we have identified in a previous study, is a product of dioxygen activation that is formed during aerobic oxidations of alcohols catalyzed by [LPd(OAc)]2(OTf)2. It is also a product of hydrogen peroxide activation during disproportionation reactions catalyzed by [LPd(OAc)]2(OTf)2. The results suggest that this trinuclear Pd compound is involved in one of the simultaneous mechanisms for the reduction of oxygen and/or the disproportionation of hydrogen peroxide during oxidation catalysis. Electrospray ionization mass spectrometry of hydrogen peroxide disproportionation reactions suggested the presence of other multinuclear Pd-O2 species in solution. Theoretical calculations of these compounds yield some insight into their structure and potential chemistry.

    View details for DOI 10.1021/jacs.5b08719

    View details for Web of Science ID 000363916600031

    View details for PubMedID 26444100

  • Challenges of metagenomics and single-cell genomics approaches for exploring cyanobacterial diversity. Photosynthesis research Davison, M., Hall, E., Zare, R., Bhaya, D. 2015; 126 (1): 135-146

    View details for DOI 10.1007/s11120-014-0066-9

    View details for PubMedID 25515769

  • Celecoxib Nanoparticles for Therapeutic Angiogenesis. ACS nano Margulis, K., Neofytou, E. A., Beygui, R. E., Zare, R. N. 2015; 9 (9): 9416-9426

    View details for DOI 10.1021/acsnano.5b04137

    View details for PubMedID 26244654

  • Detection of the Short-Lived Radical Cation Intermediate in the Electrooxidation of N,N-Dimethylaniline by Mass Spectrometry. Angewandte Chemie (International ed. in English) Brown, T. A., Chen, H., Zare, R. N. 2015; 54 (38): 11183-11185

    Abstract

    The N,N-dimethylaniline (DMA) radical cation DMA(.+) , a long-sought transient intermediate, was detected by mass spectrometry (MS) during the electrochemical oxidation of DMA. This was accomplished by coupling desorption electrospray ionization (DESI) MS with a waterwheel working electrode setup to sample the surface of the working electrode during electrochemical analysis. This study clearly shows that DESI-based electrochemical MS is capable of capturing electrochemically generated intermediates with half-lives on the order of microseconds, which is 4-5 orders of magnitude faster than previously reported electrochemical mass spectrometry techniques.

    View details for DOI 10.1002/anie.201506316

    View details for PubMedID 26352029

  • Droplet Spray Ionization from a Glass Microscope Slide: Real-Time Monitoring of Ethylene Polymerization ANALYTICAL CHEMISTRY Jiang, J., Zhang, H., Li, M., Dulay, M. T., Ingram, A. J., Li, N., You, H., Zare, R. N. 2015; 87 (16): 8057-8062

    Abstract

    Ambient ionization mass spectrometry is achieved in a simple manner by loading a sample solution onto a corner of a microscope cover glass positioned in front of the inlet to a mass spectrometer and applying a high voltage to the sample. The resulting stream of charged droplets is stable, has no contamination from the substrate platform, and can be used repeatedly. The utility of droplet spray for in situ analysis and real-time monitoring of chemical reactions was demonstrated by the bis(cyclopentadienyl)zirconium dichloride (zirconocene dichloride)/methylaluminoxane, Cp2ZrCl2/MAO, homogeneously catalyzed polymerization of ethylene in various solutions. Reaction times ranged from seconds to minutes, and catalytically active species and polymeric products of ethylene were acquired and identified by tandem mass spectrometry.

    View details for DOI 10.1021/acs.analchem.5b02390

    View details for Web of Science ID 000359892100005

  • Quantum interference between H + D-2 quasiclassical reaction mechanisms NATURE CHEMISTRY Jambrina, P. G., Herraez-Aguilar, D., Aoiz, F. J., Sneha, M., Jankunas, J., Zare, R. N. 2015; 7 (8): 661-667

    Abstract

    Interferences are genuine quantum phenomena that appear whenever two seemingly distinct classical trajectories lead to the same outcome. They are common in elastic scattering but are seldom observable in chemical reactions. Here we report experimental measurements of the state-to-state angular distribution for the H + D2 reaction using the 'photoloc' technique. For products in low rotational and vibrational states, a characteristic oscillation pattern governs backward scattering. The comparison between the experiments, rigorous quantum calculations and classical trajectories on an accurate potential energy surface allows us to trace the origin of that structure to the quantum interference between different quasiclassical mechanisms, a phenomenon analogous to that observed in the double-slit experiment.

    View details for DOI 10.1038/NCHEM.2295

    View details for Web of Science ID 000358529600012

  • Identification of Fleeting Electrochemical Reaction Intermediates Using Desorption Electrospray Ionization Mass Spectrometry. Journal of the American Chemical Society Brown, T. A., Chen, H., Zare, R. N. 2015; 137 (23): 7274-7277

    Abstract

    We report a new method for the mass spectrometric detection of fleeting reaction intermediates in electrochemical reactions utilizing a "waterwheel" working electrode setup. This setup takes inspiration from desorption electrospray ionization (DESI) mass spectrometry, where the sampling time is on the order of milliseconds, to sample directly from the surface of a working electrode for mass spectrometric analysis. We present data that show the formation of a diimine intermediate of the electrochemical oxidation of uric acid that has a lifetime in solution of 23 ms as well as data that provide evidence for the formation of a similar diimine species from the electrooxidation of xanthine, which has not been previously observed.

    View details for DOI 10.1021/jacs.5b03862

    View details for PubMedID 26030136

  • MYC oncogene overexpression drives renal cell carcinoma in a mouse model through glutamine metabolism PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Shroff, E. H., Eberlin, L. S., Dang, V. M., Gouw, A. M., Gabay, M., Adam, S. J., Bellovin, D. I., Tran, P. T., Philbrick, W. M., Garcia-Ocana, A., Casey, S. C., Li, Y., Dang, C. V., Zare, R. N., Felsher, D. W. 2015; 112 (21): 6539-6544

    Abstract

    The MYC oncogene is frequently mutated and overexpressed in human renal cell carcinoma (RCC). However, there have been no studies on the causative role of MYC or any other oncogene in the initiation or maintenance of kidney tumorigenesis. Here, we show through a conditional transgenic mouse model that the MYC oncogene, but not the RAS oncogene, initiates and maintains RCC. Desorption electrospray ionization-mass-spectrometric imaging was used to obtain chemical maps of metabolites and lipids in the mouse RCC samples. Gene expression analysis revealed that the mouse tumors mimicked human RCC. The data suggested that MYC-induced RCC up-regulated the glutaminolytic pathway instead of the glycolytic pathway. The pharmacologic inhibition of glutamine metabolism with bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl)ethyl sulfide impeded MYC-mediated RCC tumor progression. Our studies demonstrate that MYC overexpression causes RCC and points to the inhibition of glutamine metabolism as a potential therapeutic approach for the treatment of this disease.

    View details for DOI 10.1073/pnas.1507228112

    View details for PubMedID 25964345

  • Laser-Based Mass Spectrometric Assessment of Asphaltene Molecular Weight, Molecular Architecture, and Nanoaggregate Number ENERGY & FUELS Pomerantz, A. E., Wu, Q., Mullins, O. C., Zare, R. N. 2015; 29 (5): 2833-2842

    View details for DOI 10.1021/ef5020764

    View details for Web of Science ID 000355158200011

  • Microdroplet fusion mass spectrometry for fast reaction kinetics PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Lee, J. K., Kim, S., Nam, H. G., Zare, R. N. 2015; 112 (13): 3898-3903

    Abstract

    We investigated the fusion of high-speed liquid droplets as a way to record the kinetics of liquid-phase chemical reactions on the order of microseconds. Two streams of micrometer-size droplets collide with one another. The droplets that fused (13 μm in diameter) at the intersection of the two streams entered the heated capillary inlet of a mass spectrometer. The mass spectrum was recorded as a function of the distance x between the mass spectrometer inlet and the droplet fusion center. Fused droplet trajectories were imaged with a high-speed camera, revealing that the droplet fusion occurred approximately within a 500-μm radius from the droplet fusion center and both the size and the speed of the fused droplets remained relatively constant as they traveled from the droplet fusion center to the mass spectrometer inlet. Evidence is presented that the reaction effectively stops upon entering the heated inlet of the mass spectrometer. Thus, the reaction time was proportional to x and could be measured and manipulated by controlling the distance x. Kinetic studies were carried out in fused water droplets for acid-induced unfolding of cytochrome c and hydrogen-deuterium exchange in bradykinin. The kinetics of the former revealed the slowing of the unfolding rates at the early stage of the reaction within 50 μs. The hydrogen-deuterium exchange revealed the existence of two distinct populations with fast and slow exchange rates. These studies demonstrated the power of this technique to detect reaction intermediates in fused liquid droplets with microsecond temporal resolution.

    View details for DOI 10.1073/pnas.1503689112

    View details for Web of Science ID 000351914500040

    View details for PubMedID 25775573

    View details for PubMedCentralID PMC4386409

  • The role of Abcb5 alleles in susceptibility to haloperidol-induced toxicity in mice and humans. PLoS medicine Zheng, M., Zhang, H., Dill, D. L., Clark, J. D., Tu, S., Yablonovitch, A. L., Tan, M. H., Zhang, R., Rujescu, D., Wu, M., Tessarollo, L., Vieira, W., Gottesman, M. M., Deng, S., Eberlin, L. S., Zare, R. N., Billard, J., Gillet, J., Li, J. B., Peltz, G. 2015; 12 (2)

    Abstract

    We know very little about the genetic factors affecting susceptibility to drug-induced central nervous system (CNS) toxicities, and this has limited our ability to optimally utilize existing drugs or to develop new drugs for CNS disorders. For example, haloperidol is a potent dopamine antagonist that is used to treat psychotic disorders, but 50% of treated patients develop characteristic extrapyramidal symptoms caused by haloperidol-induced toxicity (HIT), which limits its clinical utility. We do not have any information about the genetic factors affecting this drug-induced toxicity. HIT in humans is directly mirrored in a murine genetic model, where inbred mouse strains are differentially susceptible to HIT. Therefore, we genetically analyzed this murine model and performed a translational human genetic association study.A whole genome SNP database and computational genetic mapping were used to analyze the murine genetic model of HIT. Guided by the mouse genetic analysis, we demonstrate that genetic variation within an ABC-drug efflux transporter (Abcb5) affected susceptibility to HIT. In situ hybridization results reveal that Abcb5 is expressed in brain capillaries, and by cerebellar Purkinje cells. We also analyzed chromosome substitution strains, imaged haloperidol abundance in brain tissue sections and directly measured haloperidol (and its metabolite) levels in brain, and characterized Abcb5 knockout mice. Our results demonstrate that Abcb5 is part of the blood-brain barrier; it affects susceptibility to HIT by altering the brain concentration of haloperidol. Moreover, a genetic association study in a haloperidol-treated human cohort indicates that human ABCB5 alleles had a time-dependent effect on susceptibility to individual and combined measures of HIT. Abcb5 alleles are pharmacogenetic factors that affect susceptibility to HIT, but it is likely that additional pharmacogenetic susceptibility factors will be discovered.ABCB5 alleles alter susceptibility to HIT in mouse and humans. This discovery leads to a new model that (at least in part) explains inter-individual differences in susceptibility to a drug-induced CNS toxicity.

    View details for DOI 10.1371/journal.pmed.1001782

    View details for PubMedID 25647612

  • The role of abcb5 alleles in susceptibility to haloperidol-induced toxicity in mice and humans. PLoS medicine Zheng, M., Zhang, H., Dill, D. L., Clark, J. D., Tu, S., Yablonovitch, A. L., Tan, M. H., Zhang, R., Rujescu, D., Wu, M., Tessarollo, L., Vieira, W., Gottesman, M. M., Deng, S., Eberlin, L. S., Zare, R. N., Billard, J., Gillet, J., Li, J. B., Peltz, G. 2015; 12 (2): e1001782

    Abstract

    We know very little about the genetic factors affecting susceptibility to drug-induced central nervous system (CNS) toxicities, and this has limited our ability to optimally utilize existing drugs or to develop new drugs for CNS disorders. For example, haloperidol is a potent dopamine antagonist that is used to treat psychotic disorders, but 50% of treated patients develop characteristic extrapyramidal symptoms caused by haloperidol-induced toxicity (HIT), which limits its clinical utility. We do not have any information about the genetic factors affecting this drug-induced toxicity. HIT in humans is directly mirrored in a murine genetic model, where inbred mouse strains are differentially susceptible to HIT. Therefore, we genetically analyzed this murine model and performed a translational human genetic association study.A whole genome SNP database and computational genetic mapping were used to analyze the murine genetic model of HIT. Guided by the mouse genetic analysis, we demonstrate that genetic variation within an ABC-drug efflux transporter (Abcb5) affected susceptibility to HIT. In situ hybridization results reveal that Abcb5 is expressed in brain capillaries, and by cerebellar Purkinje cells. We also analyzed chromosome substitution strains, imaged haloperidol abundance in brain tissue sections and directly measured haloperidol (and its metabolite) levels in brain, and characterized Abcb5 knockout mice. Our results demonstrate that Abcb5 is part of the blood-brain barrier; it affects susceptibility to HIT by altering the brain concentration of haloperidol. Moreover, a genetic association study in a haloperidol-treated human cohort indicates that human ABCB5 alleles had a time-dependent effect on susceptibility to individual and combined measures of HIT. Abcb5 alleles are pharmacogenetic factors that affect susceptibility to HIT, but it is likely that additional pharmacogenetic susceptibility factors will be discovered.ABCB5 alleles alter susceptibility to HIT in mouse and humans. This discovery leads to a new model that (at least in part) explains inter-individual differences in susceptibility to a drug-induced CNS toxicity.

    View details for DOI 10.1371/journal.pmed.1001782

    View details for PubMedID 25647612

    View details for PubMedCentralID PMC4315575

  • Transforming plastic surfaces with electrophilic backbones from hydrophobic to hydrophilic. ACS applied materials & interfaces Kim, S., Bowen, R. A., Zare, R. N. 2015; 7 (3): 1925-1931

    Abstract

    We demonstrate a simple nonaqueous reaction scheme for transforming the surface of plastics from hydrophobic to hydrophilic. The chemical modification is achieved by base-catalyzed trans-esterification with polyols. It is permanent, does not release contaminants, and causes no optical or mechanical distortion of the plastic. We present contact angle measurements to show successful modification of several types of plastics including poly(ethylene terephthalate) (PET) and polycarbonate (PC). Its applicability to blood analysis is explored using chemically modified PET blood collection tubes and found to be quite satisfactory. We expect this approach will reduce the cost of manufacturing plastic devices with optimized wettability and can be generalized to other types of plastic materials having an electrophilic linkage as its backbone.

    View details for DOI 10.1021/am507606r

    View details for PubMedID 25565370

  • Rapid and selective detection of viruses using virus-imprinted polymer films NANOSCALE Karthik, A., Margulis, K., Ren, K., Zare, R. N., Leung, L. W. 2015; 7 (45): 18998-19003

    View details for DOI 10.1039/c5nr06114h

    View details for PubMedID 26513039

  • Quantum interference between H + D2 quasiclassical reaction mechanisms. Nature chemistry Jambrina, P. G., Herráez-Aguilar, D., Aoiz, F. J., Sneha, M., Jankunas, J., Zare, R. N. 2015; 7 (8): 661–67

    Abstract

    Interferences are genuine quantum phenomena that appear whenever two seemingly distinct classical trajectories lead to the same outcome. They are common in elastic scattering but are seldom observable in chemical reactions. Here we report experimental measurements of the state-to-state angular distribution for the H + D2 reaction using the 'photoloc' technique. For products in low rotational and vibrational states, a characteristic oscillation pattern governs backward scattering. The comparison between the experiments, rigorous quantum calculations and classical trajectories on an accurate potential energy surface allows us to trace the origin of that structure to the quantum interference between different quasiclassical mechanisms, a phenomenon analogous to that observed in the double-slit experiment.

    View details for PubMedID 26201743

  • Droplet spray ionization from a glass microscope slide: real-time monitoring of ethylene polymerization. Analytical chemistry Jiang, J., Zhang, H., Li, M., Dulay, M. T., Ingram, A. J., Li, N., You, H., Zare, R. N. 2015; 87 (16): 8057–62

    Abstract

    Ambient ionization mass spectrometry is achieved in a simple manner by loading a sample solution onto a corner of a microscope cover glass positioned in front of the inlet to a mass spectrometer and applying a high voltage to the sample. The resulting stream of charged droplets is stable, has no contamination from the substrate platform, and can be used repeatedly. The utility of droplet spray for in situ analysis and real-time monitoring of chemical reactions was demonstrated by the bis(cyclopentadienyl)zirconium dichloride (zirconocene dichloride)/methylaluminoxane, Cp2ZrCl2/MAO, homogeneously catalyzed polymerization of ethylene in various solutions. Reaction times ranged from seconds to minutes, and catalytically active species and polymeric products of ethylene were acquired and identified by tandem mass spectrometry.

    View details for PubMedID 26204485

  • Miniaturized Antimicrobial Susceptibility Test by Combining Concentration Gradient Generation and Rapid Cell Culturing. Antibiotics (Basel, Switzerland) Kim, S. C., Cestellos-Blanco, S., Inoue, K., Zare, R. N. 2015; 4 (4): 455-466

    Abstract

    Effective treatment of bacterial infection relies on timely diagnosis and proper prescription of antibiotic drugs. The antimicrobial susceptibility test (AST) is one of the most crucial experimental procedures, providing the baseline information for choosing effective antibiotic agents and their dosages. Conventional methods, however, require long incubation times or significant instrumentation costs to obtain test results. We propose a lab-on-a-chip approach to perform AST in a simple, economic, and rapid manner. Our assay platform miniaturizes the standard broth microdilution method on a microfluidic device (20 × 20 mm) that generates an antibiotic concentration gradient and delivers antibiotic-containing culture media to eight 30-nL chambers for cell culture. When tested with 20 μL samples of a model bacterial strain (E. coli ATCC 25922) treated with ampicillin or streptomycin, our method allows for the determination of minimum inhibitory concentrations consistent with the microdilution test in three hours, which is almost a factor of ten more rapid than the standard method.

    View details for DOI 10.3390/antibiotics4040455

    View details for PubMedID 27025635

    View details for PubMedCentralID PMC4790307

  • Polypyrrole nanoparticles for tunable, pH-sensitive and sustained drug release NANOSCALE Samanta, D., Meiser, J. L., Zare, R. N. 2015; 7 (21): 9497-9504

    Abstract

    We report the development of a generalized pH-sensitive drug delivery system that can release any charged drug preferentially at the pH range of interest. Our system is based on polypyrrole nanoparticles (PPy NPs), synthesized via a simple one-step microemulsion technique. These nanoparticles are highly monodisperse, stable in solution over the period of a month, and have good drug loading capacity (∼15 wt%). We show that PPy NPs can be tuned to release drugs at both acidic and basic pH by varying the pH, the charge of the drug, as well as by adding small amounts of charged amphiphiles. Moreover, these NPs may be delivered locally by immobilizing them in a hydrogel. Our studies show encapsulation within a calcium alginate hydrogel results in sustained release of the incorporated drug for more than 21 days. Such a nanoparticle-hydrogel composite drug delivery system is promising for treatment of long-lasting conditions such as cancer and chronic pain which require controlled, localized, and sustained drug release.

    View details for DOI 10.1039/c5nr02196k

    View details for Web of Science ID 000354983100021

    View details for PubMedID 25931037

  • Laser desorption lamp ionization source for ion trap mass spectrometry JOURNAL OF MASS SPECTROMETRY Wu, Q., Zare, R. N. 2015; 50 (1): 160-164

    Abstract

    A two-step laser desorption lamp ionization source coupled to an ion trap mass spectrometer (LDLI-ITMS) has been constructed and characterized. The pulsed infrared (IR) output of an Nd:YAG laser (1064 nm) is directed to a target inside a chamber evacuated to ~15 Pa causing desorption of molecules from the target's surface. The desorbed molecules are ionized by a vacuum ultraviolet (VUV) lamp (filled with xenon, major wavelength at 148 nm). The resulting ions are stored and detected in a three-dimensional quadrupole ion trap modified from a Finnigan Mat LCQ mass spectrometer operated at a pressure of ≥ 0.004 Pa. The limit of detection for desorbed coronene molecules is 1.5 pmol, which is about two orders of magnitude more sensitive than laser desorption laser ionization mass spectrometry using a fluorine excimer laser (157 nm) as the ionization source. The mass spectrum of four standard aromatic compounds (pyrene, coronene, rubrene and 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (OPC)) shows that parent ions dominate. By increasing the infrared laser power, this instrument is capable of detecting inorganic compounds.

    View details for DOI 10.1002/jms.3509

    View details for Web of Science ID 000348721800022

    View details for PubMedID 25601688

  • Acceleration of Reaction in Charged Microdroplets Quarterly Reviews of Biophysics Lee, J. K., Banerjee, S., Nam, H. G., Zare, R. N. 2015
  • Laser-Based Mass Spectrometric Assessment of Asphaltene Molecular Weight, Molecular Architecture and Nanoaggregate Number Energy & Fuels Pomerantz, A. E., Wu, Q., Mullins, O. C., Zare, R. N. 2015
  • Microdroplet fusion mass spectrometry for fast reaction kinetics Proceedings of the National Academy of Sciences of the United States of America Lee, J. K., Kim, S., Nam, H. G., Zare, R. N. 2015

    View details for DOI 10.1073/pnas 1503689112

  • Mechanistic analysis of an asymmetric palladium-catalyzed conjugate addition of arylboronic acids to β-substituted cyclic enones. Chemical science Boeser, C. L., Holder, J. C., Taylor, B. L., Houk, K. N., Stoltz, B. M., Zare, R. N. 2015; 6 (3): 1917–22

    Abstract

    An asymmetric palladium-catalyzed conjugate addition reaction of arylboronic acids to enone substrates was investigated mechanistically. Desorption electrospray ionization coupled to mass spectrometry was used to identify intermediates of the catalytic cycle and delineate differences in substrate reactivity. Our findings provide evidence for the catalytic cycle proceeding through formation of an arylpalladium(II) cation, subsequent formation of an arylpalladium-enone complex, and, ultimately, formation of the new C-C bond. Reaction monitoring in both positive and negative ion modes revealed that 4-iodophenylboronic acid formed a relatively stable trimeric species under the reaction conditions.

    View details for PubMedID 25729560

  • Carl Djerassi (1923-2015). Angewandte Chemie (International ed. in English) Zare, R. N. 2015; 54 (17): 5001–2

    View details for PubMedID 25809781

  • Mechanistic analysis of an asymmetric palladium-catalyzed conjugate addition of arylboronic acids to beta-substituted cyclic enones CHEMICAL SCIENCE Boeser, C. L., Holder, J. C., Taylor, B. L., Houk, K. N., Stoltz, B. M., Zare, R. N. 2015; 6 (3): 1917-1922

    View details for DOI 10.1039/c4sc03337j

    View details for Web of Science ID 000349832600037

  • One-Pot Synthesis of Protein-Embedded Metal-Organic Frameworks with Enhanced Biological Activities NANO LETTERS Lyu, F., Zhang, Y., Zare, R. N., Ge, J., Liu, Z. 2014; 14 (10): 5761-5765

    View details for DOI 10.1021/nl5026419

    View details for Web of Science ID 000343016400044

  • Diamondosomes: Submicron Colloidosomes with Nanodiamond Shells PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION Maas, M., Bollhorst, T., Zare, R. N., Rezwan, K. 2014; 31 (10): 1067-1071

    View details for DOI 10.1002/ppsc.201400022

    View details for Web of Science ID 000343878000004

  • LprG-Mediated Surface Expression of Lipoarabinomannan Is Essential for Virulence of Mycobacterium tuberculosis PLOS PATHOGENS Gaur, R. L., Ren, K., Blumenthal, A., Bhamidi, S., Gibbs, S., Jackson, M., Zare, R. N., Ehrt, S., Ernst, J. D., Banaei, N. 2014; 10 (9)

    View details for DOI 10.1371/journal.ppat.1004376

    View details for Web of Science ID 000343014600035

  • LprG-mediated surface expression of lipoarabinomannan is essential for virulence of Mycobacterium tuberculosis. PLoS pathogens Gaur, R. L., Ren, K., Blumenthal, A., Bhamidi, S., González-Nilo, F. D., Jackson, M., Zare, R. N., Ehrt, S., Ernst, J. D., Banaei, N. 2014; 10 (9)

    Abstract

    Mycobacterium tuberculosis employs various virulence strategies to subvert host immune responses in order to persist and cause disease. Interaction of M. tuberculosis with mannose receptor on macrophages via surface-exposed lipoarabinomannan (LAM) is believed to be critical for cell entry, inhibition of phagosome-lysosome fusion, and intracellular survival, but in vivo evidence is lacking. LprG, a cell envelope lipoprotein that is essential for virulence of M. tuberculosis, has been shown to bind to the acyl groups of lipoglycans but the role of LprG in LAM biosynthesis and localization remains unknown. Using an M. tuberculosis lprG mutant, we show that LprG is essential for normal surface expression of LAM and virulence of M. tuberculosis attributed to LAM. The lprG mutant had a normal quantity of LAM in the cell envelope, but its surface was altered and showed reduced expression of surface-exposed LAM. Functionally, the lprG mutant was defective for macrophage entry and inhibition of phagosome-lysosome fusion, was attenuated in macrophages, and was killed in the mouse lung with the onset of adaptive immunity. This study identifies the role of LprG in surface-exposed LAM expression and provides in vivo evidence for the essential role surface LAM plays in M. tuberculosis virulence. Findings have translational implications for therapy and vaccine development.

    View details for DOI 10.1371/journal.ppat.1004376

    View details for PubMedID 25232742

    View details for PubMedCentralID PMC4169494

  • Fall, recovery, and characterization of the Novato L6 chondrite breccia METEORITICS & PLANETARY SCIENCE Jenniskens, P., Rubin, A. E., Yin, Q., Sears, D. W., Sandford, S. A., Zolensky, M. E., Krot, A. N., Blair, L., Kane, D., Utas, J., Verish, R., Friedrich, J. M., Wimpenny, J., Eppich, G. R., Ziegler, K., Verosub, K. L., Rowland, D. J., Albers, J., Gural, P. S., Grigsby, B., Fries, M. D., Matson, R., Johnston, M., Silber, E., Brown, P., Yamakawa, A., Sanborn, M. E., Laubenstein, M., Welten, K. C., Nishiizumi, K., Meier, M. M., Busemann, H., Clay, P., Caffee, M. W., Schmitt-Kopplin, P., Hertkorn, N., Glavin, D. P., Callahan, M. P., Dworkin, J. P., Wu, Q., Zare, R. N., Grady, M., Verchovsky, S., Emel'yanenko, V., Naroenkov, S., Clark, D. L., Girten, B., Worden, P. S. 2014; 49 (8): 1388-1425

    View details for DOI 10.1111/maps.12323

    View details for Web of Science ID 000340875900007

  • Alteration of the lipid profile in lymphomas induced by MYC overexpression. Proceedings of the National Academy of Sciences of the United States of America Eberlin, L. S., Gabay, M., Fan, A. C., Gouw, A. M., Tibshirani, R. J., Felsher, D. W., Zare, R. N. 2014; 111 (29): 10450-10455

    Abstract

    Overexpression of the v-myc avian myelocytomatosis viral oncogene homolog (MYC) oncogene is one of the most commonly implicated causes of human tumorigenesis. MYC is known to regulate many aspects of cellular biology including glucose and glutamine metabolism. Little is known about the relationship between MYC and the appearance and disappearance of specific lipid species. We use desorption electrospray ionization mass spectrometry imaging (DESI-MSI), statistical analysis, and conditional transgenic animal models and cell samples to investigate changes in lipid profiles in MYC-induced lymphoma. We have detected a lipid signature distinct from that observed in normal tissue and in rat sarcoma-induced lymphoma cells. We found 104 distinct molecular ions that have an altered abundance in MYC lymphoma compared with normal control tissue by statistical analysis with a false discovery rate of less than 5%. Of these, 86 molecular ions were specifically identified as complex phospholipids. To evaluate whether the lipid signature could also be observed in human tissue, we examined 15 human lymphoma samples with varying expression levels of MYC oncoprotein. Distinct lipid profiles in lymphomas with high and low MYC expression were observed, including many of the lipid species identified as significant for MYC-induced animal lymphoma tissue. Our results suggest a relationship between the appearance of specific lipid species and the overexpression of MYC in lymphomas.

    View details for DOI 10.1073/pnas.1409778111

    View details for PubMedID 24994904

  • Bactericidal Activity of Partially Oxidized Nanodiamonds ACS NANO Wehling, J., Dringen, R., Zare, R. N., Maas, M., Rezwan, K. 2014; 8 (6): 6475-6483

    Abstract

    Nanodiamonds are a class of carbon-based nanoparticles that are rapidly gaining attention, particularly for biomedical applications, i.e., as drug carriers, for bioimaging, or as implant coatings. Nanodiamonds have generally been considered biocompatible with a broad variety of eukaryotic cells. We show that, depending on their surface composition, nanodiamonds kill Gram-positive and -negative bacteria rapidly and efficiently. We investigated six different types of nanodiamonds exhibiting diverse oxygen-containing surface groups that were created using standard pretreatment methods for forming nanodiamond dispersions. Our experiments suggest that the antibacterial activity of nanodiamond is linked to the presence of partially oxidized and negatively charged surfaces, specifically those containing acid anhydride groups. Furthermore, proteins were found to control the bactericidal properties of nanodiamonds by covering these surface groups, which explains the previously reported biocompatibility of nanodiamonds. Our findings describe the discovery of an exciting property of partially oxidized nanodiamonds as a potent antibacterial agent.

    View details for DOI 10.1021/nn502230m

    View details for Web of Science ID 000338089200117

    View details for PubMedID 24861876

  • Trinuclear pd3 o2 intermediate in aerobic oxidation catalysis. Angewandte Chemie (International ed. in English) Ingram, A. J., Solis-Ibarra, D., Zare, R. N., Waymouth, R. M. 2014; 53 (22): 5648-5652

    Abstract

    The activation of O2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd(II))3(μ(3)-O)2](2+) (L=2,9-dimethylphenanthroline), was identified during the [LPd(OAc)]2(OTf)2-catalyzed aerobic oxidation of 1,2-propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd3O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.

    View details for DOI 10.1002/anie.201400134

    View details for PubMedID 24711099

  • Constant Asphaltene Molecular and Nanoaggregate Mass in a Gravitationally Segregated Reservoir ENERGY & FUELS Wu, Q., Seifert, D. J., Pomerantz, A. E., Mullins, O. C., Zare, R. N. 2014; 28 (5): 3010-3015

    View details for DOI 10.1021/ef500281s

    View details for Web of Science ID 000336199300017

  • Visualizing Dermal Permeation of Sodium Channel Modulators by Mass Spectrometric Imaging JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Eberlin, L. S., Mulcahy, J. V., Tzabazis, A., Zhang, J., Liu, H., Logan, M. M., Roberts, H. J., Lee, G. K., Yeomans, D. C., Du Bois, J., Zare, R. N. 2014; 136 (17): 6401-6405

    Abstract

    Determining permeability of a given compound through human skin is a principal challenge owing to the highly complex nature of dermal tissue. We describe the application of an ambient mass spectrometry imaging method for visualizing skin penetration of sodium channel modulators, including novel synthetic analogs of natural neurotoxic alkaloids, topically applied ex vivo to human skin. Our simple and label-free approach enables successful mapping of the transverse and lateral diffusion of small molecules having different physicochemical properties without the need for extensive sample preparation.

    View details for DOI 10.1021/ja501635u

    View details for Web of Science ID 000335369200044

    View details for PubMedID 24708172

    View details for PubMedCentralID PMC4017602

  • Coherent superposition of M-states in a single rovibrational level of H2 by Stark-induced adiabatic Raman passage. journal of chemical physics Mukherjee, N., Dong, W., Zare, R. N. 2014; 140 (7): 074201-?

    Abstract

    We prepare an ensemble of isolated rovibrationally excited (v = 1, J = 2) H2 molecules in a phase-locked superposition of magnetic sublevels M using Stark-induced adiabatic Raman passage with linearly polarized single-mode pump (at 532 nm, ∼6 ns pulse duration, 200 mJ/pulse) and Stokes (699 nm, ∼4 ns pulse duration, 20 mJ/pulse) laser excitation. A biaxial superposition state, given by [Formula: see text], is prepared with linearly but cross-polarized pump and Stokes laser pulses copropagating along the quantization z-axis. The degree of phase coherence is measured by using the O(2) line of the H2 E,F-X (0,1) band via 2 + 1 resonance enhanced multiphoton ionization (REMPI) at 210.8 nm by recording interference fringes in the REMPI signal in a time-of-flight mass spectrometer as the direction of the UV laser polarization is rotated using a half-wave plate. Nearly 60% population transfer from H2 (v = 0, J = 0) ground state to the superposition state in H2 (v = 1, J = 2) is measured from the depletion of the Q(0) line of the E,F-X (0,0) band as the Stokes frequency is tuned across the (v = 0, J = 0) → (v = 1, J = 2) Raman resonance.

    View details for DOI 10.1063/1.4865131

    View details for PubMedID 24559344

  • Molecular assessment of surgical-resection margins of gastric cancer by mass-spectrometric imaging. Proceedings of the National Academy of Sciences of the United States of America Eberlin, L. S., Tibshirani, R. J., Zhang, J., Longacre, T. A., Berry, G. J., Bingham, D. B., Norton, J. A., Zare, R. N., Poultsides, G. A. 2014; 111 (7): 2436-2441

    Abstract

    Surgical resection is the main curative option for gastrointestinal cancers. The extent of cancer resection is commonly assessed during surgery by pathologic evaluation of (frozen sections of) the tissue at the resected specimen margin(s) to verify whether cancer is present. We compare this method to an alternative procedure, desorption electrospray ionization mass spectrometric imaging (DESI-MSI), for 62 banked human cancerous and normal gastric-tissue samples. In DESI-MSI, microdroplets strike the tissue sample, the resulting splash enters a mass spectrometer, and a statistical analysis, here, the Lasso method (which stands for least absolute shrinkage and selection operator and which is a multiclass logistic regression with L1 penalty), is applied to classify tissues based on the molecular information obtained directly from DESI-MSI. The methodology developed with 28 frozen training samples of clear histopathologic diagnosis showed an overall accuracy value of 98% for the 12,480 pixels evaluated in cross-validation (CV), and 97% when a completely independent set of samples was tested. By applying an additional spatial smoothing technique, the accuracy for both CV and the independent set of samples was 99% compared with histological diagnoses. To test our method for clinical use, we applied it to a total of 21 tissue-margin samples prospectively obtained from nine gastric-cancer patients. The results obtained suggest that DESI-MSI/Lasso may be valuable for routine intraoperative assessment of the specimen margins during gastric-cancer surgery.

    View details for DOI 10.1073/pnas.1400274111

    View details for PubMedID 24550265

  • Is the simplest chemical reaction really so simple? PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Jankunas, J., Sneha, M., Zare, R. N., Bouakline, F., Althorpe, S. C., Herraez-Aguilar, D., Javier Aoiz, F. 2014; 111 (1): 15-20

    Abstract

    Modern computational methods have become so powerful for predicting the outcome for the H + H2 → H2 + H bimolecular exchange reaction that it might seem further experiments are not needed. Nevertheless, experiments have led the way to cause theorists to look more deeply into this simplest of all chemical reactions. The findings are less simple.

    View details for DOI 10.1073/pnas.1315725111

    View details for Web of Science ID 000329350700031

    View details for PubMedID 24367084

    View details for PubMedCentralID PMC3890794

  • Modes of Activation of Organometallic Iridium Complexes for Catalytic Water and C-H Oxidation INORGANIC CHEMISTRY Ingram, A. J., Wolk, A. B., Flender, C., Zhang, J., Johnson, C. J., Hintermair, U., Crabtree, R. H., Johnson, M. A., Zare, R. N. 2014; 53 (1): 423-433

    Abstract

    Sodium periodate (NaIO4) is added to Cp*Ir(III) (Cp* = C5Me5(-)) or (cod)Ir(I) (cod = cyclooctadiene) complexes, which are water and C-H oxidation catalyst precursors, and the resulting aqueous reaction is investigated from milliseconds to seconds using desorption electrospray ionization, electrosonic spray ionization, and cryogenic ion vibrational predissociation spectroscopy. Extensive oxidation of the Cp* ligand is observed, likely beginning with electrophilic C-H hydroxylation of a Cp* methyl group followed by nonselective pathways of further oxidative degradation. Evidence is presented that the supporting chelate ligand in Cp*Ir(chelate) precursors influences the course of oxidation and is neither eliminated from the coordination sphere nor oxidatively transformed. Isomeric products of initial Cp* oxidation are identified and structurally characterized by vibrational spectroscopy in conjunction with density functional theory (DFT) modeling. Less extensive but more rapid oxidation of the cod ligand is also observed in the (cod)Ir(I) complexes. The observations are consistent with the proposed role of Cp* and cod as sacrificial placeholder ligands that are oxidatively removed from the precursor complexes under catalytic conditions.

    View details for DOI 10.1021/ic402390t

    View details for Web of Science ID 000329529800051

    View details for PubMedID 24228617

  • Coherent Superposition of M-States in a Single Rovibrational Level of H2 by Start-Induced Adiabatic Raman Passage J. Chem. Phys. Mukherjee, N., Dong, W., Zare, R. N. 2014; 140: 074201
  • Direct Synthesis of Protein-Incorporated Metal-Organic Framework Hybrid Materials NANO LETTERS Lyu, F., Zhang, Y., Zare, R. N., Ge, J., Liu, Z. 2014; 14: 5761-5765
  • Speciation and decomposition pathways of ruthenium catalysts used for selective C-H hydroxylation CHEMICAL SCIENCE Flender, C., Adams, A. M., Roizen, J. L., McNeill, E., Du Bois, J., Zare, R. N. 2014; 5 (8): 3309-3314

    View details for DOI 10.1039/c4sc01050g

    View details for Web of Science ID 000338652900046

  • "In questo modo io scrivo" Zare, R. N. Aracne editrice. 2014
  • Do Identical Polar Diatomic Molecules Form Stacked or Linear Dimers? Do Identical Polar Diatomic Molecules Form Stacked or Linear Dimers? Williams, C. W., Zare, R. N., Arunan, E. 2014: 704-712
  • Challenges of Metagenomics and Single-Cell Genomics Approaches for Exploring Cyanobacterial Diversity Challenges of Metagenomics and Single-Cell Genomics Approaches for Exploring Cyanobacterial Diversity Davison, M., Hall, E., Zare, R. N., Bhaya, D. 2014

    View details for DOI 10.1007/s11120-014-0066-9

  • LprG-Mediated Surface Expression of Lipoarabinomannan Is Essential for Virulence of Mycobacterium tuberculosis LprG-Mediated Surface Expression of Lipoarabinomannan Is Essential for Virulence of Mycobacterium tuberculosis Gaur, R. L., Ren, K., Blumenthal, A., Bhamidi, S., Gibbs, S., Jackson, M., Zare, R. N., Ehrt, S., Ernst, J. D., Banaei, N. 2014
  • Molecular Assessment of Gastric Cancer Surgical Resection Margins by Mass Spectrometric Imaging Proc. Nat. Acad. Science Eberlin, L. S., Tibshirani, R., Zhang, J., Longacre, T. A., Berry, G., Bingham, D. B., Norton, J. A., Zare, R. N., Poultsides, G. A. 2014: 2436–2441
  • Why Some Pool Shots Are More Difficult Than Others Resonance Jankunas, J., Zare, R. N. 2014; 19: 116-122
  • Laser-Based Mass Spectrometric Determination of Aggregation Numbers for Petroleum- and Coal-Derived Asphaltenes ENERGY & FUELS Wu, Q., Pomerantz, A. E., Mullins, O. C., Zare, R. N. 2014; 28 (1): 475-482

    View details for DOI 10.1021/ef401958n

    View details for Web of Science ID 000330018200052

  • Diamondosomes: Submicron Colloidosomes with Nanodiamond Shells Part. Part. System. Charact. Maas, M., Bollhorst, T., Zare, R. N., Rezwan, K. 2014

    View details for DOI 10.1002/ppsc.201400022

  • Speciation and Decomposition Pathways of Ruthenium Catalysts Used for Selective C-H Hydroxylation Chem. Sci. Flender, C., Adams, A. M., Roizen, J. L., McNeill, E., Du Bois, J., Zare, R. N. 2014; 5 (8): 3309-3314

    View details for DOI 10.1039/C4SC01050G

  • Simultaneous Measurement of Reactive and Inelastic Scattering: Differential Cross Section of the H + HD -> HD(v ', j ') + H Reaction ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS Jankunas, J., Sneha, M., Zare, R. N., Bouakline, F., Althorpe, S. C. 2013; 227 (9-11): 1281-1299

    View details for DOI 10.1524/zpch.2013.0407

    View details for Web of Science ID 000327861100008

  • Hunt for geometric phase effects in H plus HD -> HD(v ', j ') plus H JOURNAL OF CHEMICAL PHYSICS Jankunas, J., Sneha, M., Zare, R. N., Bouakline, F., Althorpe, S. C. 2013; 139 (14)

    Abstract

    An attempt has been made to measure the theoretically predicted manifestation of a geometric phase in the differential cross section for the H + HD → HD(v' = 2, j' = 5) + H reaction at a center-of-mass collision energy of 1.44 eV (33.2 kcal∕mol). Minute oscillatory differences between calculated differential cross sections that take into account and ignore the effect of geometric phase have proven to be beyond our experimental resolution in spite of the collection of more than 44,000 ions.

    View details for DOI 10.1063/1.4821601

    View details for Web of Science ID 000325780800035

    View details for PubMedID 24116628

  • Rapid Detection of Phenol Using a Membrane Containing Laccase Nanoflowers CHEMISTRY-AN ASIAN JOURNAL Zhu, L., Gong, L., Zhang, Y., Wang, R., Ge, J., Liu, Z., Zare, R. N. 2013; 8 (10): 2358-2360

    View details for DOI 10.1002/asia.201300020

    View details for Web of Science ID 000324748600011

    View details for PubMedID 23423764

  • Electrooxidation of alcohols catalyzed by amino alcohol ligated ruthenium complexes. Journal of the American Chemical Society Brownell, K. R., McCrory, C. C., Chidsey, C. E., Perry, R. H., Zare, R. N., Waymouth, R. M. 2013; 135 (38): 14299-14305

    Abstract

    Ruthenium transfer hydrogenation catalysts physisorbed onto edge-plane graphite electrodes are active electrocatalysts for the oxidation of alcohols. Electrooxidation of CH3OH (1.23 M) in a buffered aqueous solution at pH 11.5 with [(η(6)-p-cymene)(η(2)-N,O-(1R,2S)-cis-1-amino-2-indanol)]Ru(II)Cl (2) on edge-plane graphite exhibits an onset current at 560 mV vs NHE. Koutecky-Levich analysis at 750 mV reveals a four-electron oxidation of methanol with a rate of 1.35 M(-1) s(-1). Mechanistic investigations by (1)H NMR, cyclic voltammetry, and desorption electrospray ionization mass spectrometry indicate that the electroxidation of methanol to generate formate is mediated by surface-supported Ru-oxo complexes.

    View details for DOI 10.1021/ja4055564

    View details for PubMedID 24044700

  • Lysis of a Single Cyanobacterium for Whole Genome Amplification MICROMACHINES Hall, E. W., Kim, S., Appadoo, V., Zare, R. N. 2013; 4 (3): 321-332

    View details for DOI 10.3390/mi4030321

    View details for Web of Science ID 000325021600003

  • Optical preparation of H-2 rovibrational levels with almost complete population transfer JOURNAL OF CHEMICAL PHYSICS Dong, W., Mukherjee, N., Zare, R. N. 2013; 139 (7)

    Abstract

    Using stimulated Raman adiabatic passage (SARP), it is possible, in principle, to transfer all the population in a rovibrational level of an isolated diatomic molecule to an excited rovibrational level. We use an overlapping sequence of pump (532 nm) and dump (683 nm) single-mode laser pulses of unequal fluence to prepare isolated H2 molecules in a molecular beam. In a first series of experiments we were able to transfer more than half the population to an excited rovibrational level [N. Mukherjee, W. R. Dong, J. A. Harrison, and R. N. Zare, J. Chem. Phys. 138(5), 051101-1-051101-4 (2013)]. Since then, we have achieved almost complete transfer (97% ± 7%) of population from the H2 (v = 0, J = 0) ground rovibrational level to the H2 (v = 1, J = 0) excited rovibrational level. An explanation is presented of the SARP process and how these results are obtained.

    View details for DOI 10.1063/1.4818526

    View details for Web of Science ID 000323509900023

    View details for PubMedID 23968084

  • Minimization of fragmentation and aggregation by laser desorption laser ionization mass spectrometry. Journal of the American Society for Mass Spectrometry Wu, Q., Pomerantz, A. E., Mullins, O. C., Zare, R. N. 2013; 24 (7): 1116-1122

    Abstract

    Measuring average quantities in complex mixtures can be challenging for mass spectrometry, as it requires ionization and detection with nearly equivalent cross-section for all components, minimal matrix effect, and suppressed signal from fragments and aggregates. Fragments and aggregates are particularly troublesome for complex mixtures, where they can be incorrectly assigned as parent ions. Here we study fragmentation and aggregation in six aromatic model compounds as well as petroleum asphaltenes (a naturally occurring complex mixture) using two laser-based ionization techniques: surface assisted laser desorption ionization (SALDI), in which a single laser desorbs and ionizes solid analytes; and laser ionization laser desorption mass spectrometry (L(2)MS), in which desorption and ionization are separated spatially and temporally with independent lasers. Model compounds studied include molecules commonly used as matrices in single laser ionization techniques such as matrix assisted laser desorption ionization (MALDI). We find significant fragmentation and aggregation in SALDI, such that individual fragment and aggregate peaks are typically more intense than the parent peak. These fragment and aggregate peaks are expected in MALDI experiments employing these compounds as matrices. On the other hand, we observe no aggregation and only minimal fragmentation in L(2)MS. These results highlight some advantages of L(2)MS for analysis of complex mixtures such as asphaltenes.

    View details for DOI 10.1007/s13361-013-0636-7

    View details for PubMedID 23633019

  • Sorting Inactivated Cells Using Cell-Imprinted Polymer Thin Films ACS NANO Ren, K., Banaei, N., Zare, R. N. 2013; 7 (7): 6031-6036

    Abstract

    Previous work showed that cell imprinting in a polydimethylsiloxane (PDMS) film produced artificial receptors to cells by template-assisted rearrangement of functional groups on the surface of the polymer thin film which facilitated cell capture in the polymer surface indentations by size, shape, and most importantly chemical recognition. We report here that inactivation of cells by treatment with formaldehyde (4%), or glutaraldehyde (2%), or a combination of the two leads to markedly improved capture selectivity (a factor of 3) when cells to be analyzed are inactivated in the same manner. The enhanced capture efficiency compared to living cells results from two factors: (1) rigidification of the cell surface through crosslinking of amine groups by the aldehyde; and (2) elimination of chemicals excreted from living cells which interfere with the fidelity of the cell imprinting process. Moreover, cell inactivation has the advantage of removing biohazard risks associated with working with virulent bacteria. These results are demonstrated using different strains of mycobacterium tuberculosis.

    View details for DOI 10.1021/nn401768s

    View details for Web of Science ID 000322417400045

    View details for PubMedID 23725546

  • Functional protein-organic/inorganic hybrid nanomaterials WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY Wang, R., Zhang, Y., Lu, D., Ge, J., Liu, Z., Zare, R. N. 2013; 5 (4): 320-328

    Abstract

    Nanotechnology offers immense opportunities for regulating and improving biological functions of proteins in vitro. Recent years have witnessed growing efforts to develop protein-incorporated hybrid nanostructured materials with potential applications in functional materials, enzymatic catalysis, drug delivery, and analytical sciences. In this review, recent advances in functional protein-organic/inorganic hybrid nanomaterials are discussed with an emphasis on the novel preparation methods, resulting nanostructures, and their potential applications in drug delivery and enzymatic catalysis. Future directions toward the rational design of these bionanomaterials are suggested.

    View details for DOI 10.1002/wnan.1210

    View details for Web of Science ID 000320403500003

    View details for PubMedID 23362008

  • Chemoselective pd-catalyzed oxidation of polyols: synthetic scope and mechanistic studies. Journal of the American Chemical Society Chung, K., Banik, S. M., De Crisci, A. G., Pearson, D. M., Blake, T. R., Olsson, J. V., Ingram, A. J., Zare, R. N., Waymouth, R. M. 2013; 135 (20): 7593-7602

    Abstract

    The regio- and chemoselective oxidation of unprotected vicinal polyols with [(neocuproine)Pd(OAc)]2(OTf)2 (1) (neocuproine = 2,9-dimethyl-1,10-phenanthroline) occurs readily under mild reaction conditions to generate α-hydroxy ketones. The oxidation of vicinal diols is both faster and more selective than the oxidation of primary and secondary alcohols; vicinal 1,2-diols are oxidized selectively to hydroxy ketones, whereas primary alcohols are oxidized in preference to secondary alcohols. Oxidative lactonization of 1,5-diols yields cyclic lactones. Catalyst loadings as low as 0.12 mol % in oxidation reactions on a 10 g scale can be used. The exquisite selectivity of this catalyst system is evident in the chemoselective and stereospecific oxidation of the polyol (S,S)-1,2,3,4-tetrahydroxybutane [(S,S)-threitol] to (S)-erythrulose. Mechanistic, kinetic, and theoretical studies revealed that the rate laws for the oxidation of primary and secondary alcohols differ from those of diols. Density functional theory calculations support the conclusion that β-hydride elimination to give hydroxy ketones is product-determining for the oxidation of vicinal diols, whereas for primary and secondary alcohols, pre-equilibria favoring primary alkoxides are product-determining. In situ desorption electrospray ionization mass spectrometry (DESI-MS) revealed several key intermediates in the proposed catalytic cycle.

    View details for DOI 10.1021/ja4008694

    View details for PubMedID 23659308

  • Characterization of MYC-Induced Tumorigenesis by in Situ Lipid Profiling ANALYTICAL CHEMISTRY Perry, R. H., Bellovin, D. I., Shroff, E. H., Ismail, A. I., Zabuawala, T., Felsher, D. W., Zare, R. N. 2013; 85 (9): 4259-4262

    Abstract

    We apply desorption electrospray ionization mass spectrometry imaging (DESI-MSI) to provide an in situ lipidomic profile of genetically modified tissues from a conditional transgenic mouse model of MYC-induced hepatocellular carcinoma (HCC). This unique, label-free approach of combining DESI-MSI with the ability to turn specific genes on and off has led to the discovery of highly specific lipid molecules associated with MYC-induced tumor onset. We are able to distinguish normal from MYC-induced malignant cells. Our approach provides a strategy to define a precise molecular picture at a resolution of about 200 μm that may be useful in identifying lipid molecules that define how the MYC oncogene initiates and maintains tumorigenesis.

    View details for DOI 10.1021/ac400479j

    View details for Web of Science ID 000318756100008

    View details for PubMedID 23560736

  • Disagreement between theory and experiment grows with increasing rotational excitation of HD(v ', j ') product for the H + D-2 reaction JOURNAL OF CHEMICAL PHYSICS Jankunas, J., Sneha, M., Zare, R. N., Bouakline, F., Althorpe, S. C. 2013; 138 (9)

    Abstract

    The Photoloc technique has been employed to measure the state-resolved differential cross sections of the HD(v', j(')) product in the reaction H + D2 over a wide range of collision energies and internal states. The experimental results were compared with fully dimensional, time-dependent quantum mechanical calculations on the refined Boothroyd-Keogh-Martin-Peterson potential energy surface. We find nearly perfect agreement between theory and experiment for HD(v', j(')) product states with low to medium rotational excitation, e.g., HD(v' = 1, j(') = 3) at a collision energy, Ecoll, of 1.72 eV, HD(v' = 1, j(') = 3, 5) at Ecoll = 1.97 eV, and HD(v' = 3, j(') = 3) at Ecoll = 1.97 eV. As the rotational angular momentum, j('), of HD(v', j(')) increases, the agreement between theoretical predictions and experimental measurements worsens but not in a simple fashion. A moderate disagreement between theory and experiment has been found for HD(v' = 0, j(') = 12) at Ecoll = 1.76 eV and increased monotonically for HD(v' = 0, j(') = 13) at Ecoll = 1.74 eV, HD(v' = 0, j(') = 14) at Ecoll = 1.72 eV, and HD(v' = 0, j(') = 15) at Ecoll = 1.70 eV. Disagreement was not limited to vibrationless HD(v', j(')) product states: HD(v' = 1, j(') = 12) at Ecoll = 1.60 eV and HD(v' = 3, j(') = 8, 10) at Ecoll = 1.97 eV followed a similar trend. Theoretical calculations suggest more sideways∕forward scattering than has been observed experimentally for high j(') HD(v', j(')) states. The source of this discrepancy is presently unknown but might be the result of inaccuracy in the potential energy surface.

    View details for DOI 10.1063/1.4793557

    View details for Web of Science ID 000315874200028

    View details for PubMedID 23485297

  • Preparing amorphous hydrophobic drug nanoparticles by nanoporous membrane extrusion NANOMEDICINE Guo, P., Hsu, T. M., Zhao, Y., Martin, C. R., Zare, R. N. 2013; 8 (3): 333-341

    Abstract

    The aim of the present study was to develop a simple and straightforward method for formulating hydrophobic drugs into nanoparticulate form in a scalable and inexpensive manner.The nanoporous membrane extrusion (NME) method was used to prepare hydrophobic drug nanoparticles. NME is based on the induced precipitation of drug-loaded nanoparticles at the exits of nanopores. Three common hydrophobic drug models (silymarin, β-carotene and butylated hydroxytoluene) were tested. The authors carefully investigated the morphology, crystallinity and dissolution profile of the resulting nanoparticles.Using NME, the authors successfully prepared rather uniform drug nanoparticles (∼100 nm in diameter). These nanoparticles were amorphous and show an improved dissolution profile compared with untreated drug powders.These studies suggest that NME could be used as a general method to produce nanoparticles of hydrophobic drugs.

    View details for DOI 10.2217/NNM.12.119

    View details for Web of Science ID 000315973900012

    View details for PubMedID 22943127

  • Communication: Transfer of more than half the population to a selected rovibrational state of H-2 by Stark-induced adiabatic Raman passage JOURNAL OF CHEMICAL PHYSICS Mukherjee, N., Dong, W., Harrison, J. A., Zare, R. N. 2013; 138 (5)

    Abstract

    By using Stark-induced adiabatic Raman passage (SARP) with partially overlapping nanosecond pump (532 nm) and Stokes (683 nm) laser pulses, 73% ± 6% of the initial ground vibrational state population of H(2) (v = 0, J = 0) is transferred to the single vibrationally excited eigenstate (v = 1, J = 0). In contrast to other Stark chirped Raman adiabatic passage techniques, SARP transfers population from the initial ground state to a vibrationally excited target state of the ground electronic surface without using an intermediate vibronic resonance within an upper electronic state. Parallel linearly polarized, co-propagating pump and Stokes laser pulses of respective durations 6 ns and 4.5 ns, are combined with a relative delay of ~4 ns before orthogonally intersecting the molecular beam of H(2). The pump and Stokes laser pulses have fluences of ~10 J/mm(2) and ~1 J/mm(2), respectively. The intense pump pulse generates the necessary sweeping of the Raman resonance frequency by ac (second-order) Stark shifting the rovibrational levels. As the frequency of the v = 0 → v = 1 Raman transition is swept through resonance in the presence of the strong pump and the weaker delayed Stokes pulses, the population of (v = 0, J = 0) is coherently transferred via an adiabatic passage to (v = 1, J = 0). A quantitative measure of the population transferred to the target state is obtained from the depletion of the ground-state population using 2 + 1 resonance enhanced multiphoton ionization (REMPI) in a time-of-flight mass spectrometer. The depletion is measured by comparing the REMPI signal of (v = 0, J = 0) at Raman resonance with that obtained when the Stokes pulse is detuned from the Stark-shifted Raman resonance. No depletion is observed with either the pump or the Stokes pulses alone, confirming that the measured depletion is indeed caused by the SARP-induced population transfer from the ground to the target state and not by the loss of molecules from photoionization or photodissociation. The two-photon resonant UV pulse used for REMPI detection is delayed by 20 ns with respect to the pump pulse to avoid the ac Stark shift originating from the pump and Stokes laser pulses. This experiment demonstrates the feasibility of preparing a large ensemble of isolated molecules in a preselected single quantum state without requiring an intermediate vibronic resonance.

    View details for DOI 10.1063/1.4790402

    View details for Web of Science ID 000314746400001

    View details for PubMedID 23406090

  • The Hydrogen Games and Other Adventures in Chemistry ANNUAL REVIEW OF PHYSICAL CHEMISTRY, VOL 64 Zare, R. N. 2013; 64: 1-19

    Abstract

    I seem to have started off on the wrong foot in life, but I am extremely fortunate that I soon found my footing in the company of physical chemists. I consider myself to be very lucky to be doing something that constantly brings me in contact with bright minds, stimulating conversations, and exciting experiments. My work has allowed me to learn astounding facts about the molecules and atoms that make up our surroundings and ourselves. For this article, I focus on one aspect of my research, understanding the fundamental principles of the simple reaction between a hydrogen atom and a hydrogen molecule. Although my group and others have been studying this seemingly simple reaction for well over 30 years, it continues to provoke questions about the properties of matter.

    View details for DOI 10.1146/annurev-physchem-040412-110115

    View details for Web of Science ID 000321771600001

    View details for PubMedID 22974411

  • Temperature-responsive enzyme-polymer nanoconjugates with enhanced catalytic activities in organic media CHEMICAL COMMUNICATIONS Zhu, J., Zhang, Y., Lu, D., Zare, R. N., Ge, J., Liu, Z. 2013; 49 (54): 6090-6092

    Abstract

    A general approach for preparing enzyme-polymer nanoconjugates that respond to temperature in organic media is presented. These nanoconjugates readily dissolve in organic solvents for homogenous catalysis at 40 °C and showed greatly enhanced apparent catalytic activities. The recovery of the soluble enzyme-polymer nanoconjugates is accomplished by temperature-induced precipitation.

    View details for DOI 10.1039/c3cc42493f

    View details for Web of Science ID 000320199000027

    View details for PubMedID 23727906

  • American universities at risk. Angewandte Chemie (International ed. in English) Zare, R. N. 2013; 52 (1): 112–13

    View details for PubMedID 23208762

  • Temperature-Responsive Enzyme-Polymer Nanoconjugates with Enhanced Catalytic Activities in Organic Solvents ChemComm Zhu, J., Zhang, Y., Lu, D., Zare, R. N., Ge, J., Liu, Z. 2013; 49: 6090-6092
  • Optical Preparation of H2 Rovibrational Levels with Almost Complete Population Transfer J. Chem. Phys. Dong, W., Mukherjee, N., Zare, R. N. 2013; 139
  • Sorting Inactivated Celss Using Cell-Imprinted Polymer Thin Films ACS Nano Ren, K., Banaei, N., Zare, R. N. 2013; 7: 6031-6036
  • Protein-Polymer Hybrid Nanoparticles for Drug Delivery SMALL Ge, J., Neofytou, E., Lei, J., Beygui, R. E., Zare, R. N. 2012; 8 (23): 3573-3578

    Abstract

    Amphiphilic bovine serum albumin-poly(methyl methacrylate) conjugate forms nanoparticles with the uniform size of ~100 nm by self-assembling. Loaded with the hydrophobic anti-tumor drug camptothecin, the nanoparticle efficiently delivers drugs into cancer cells, and thus inhibits ~79% of tumor growth in animals compared with free drug.

    View details for DOI 10.1002/smll.201200889

    View details for Web of Science ID 000312214400004

    View details for PubMedID 22888073

  • Capturing fleeting intermediates in a catalytic C-H amination reaction cycle PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Perry, R. H., Cahill, T. J., Roizen, J. L., Du Bois, J., Zare, R. N. 2012; 109 (45): 18295-18299

    Abstract

    We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C-H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C-H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes.

    View details for DOI 10.1073/pnas.1207600109

    View details for Web of Science ID 000311156700025

    View details for PubMedID 23091019

    View details for PubMedCentralID PMC3494934

  • H + D-2 Reaction Dynamics in the Limit of Low Product Recoil Energy JOURNAL OF PHYSICAL CHEMISTRY LETTERS Aldegunde, J., Herraez-Aguilar, D., Jambrina, P. G., Aoiz, F. J., Jankunas, J., Zare, R. N. 2012; 3 (20): 2959-2963

    View details for DOI 10.1021/jz301192f

    View details for Web of Science ID 000310177200007

  • Isomeric differentiation of polycyclic aromatic hydrocarbons using silver nitrate reactive desorption electrospray ionization mass spectrometry RAPID COMMUNICATIONS IN MASS SPECTROMETRY Eftekhari, M., Ismail, A. I., Zare, R. N. 2012; 26 (17): 1985-1992

    Abstract

    Polycyclic aromatic hydrocarbons (PAHs) are nonpolar and difficult to detect by desorption electrospray ionization. We present a new detection method based on cationization with silver ions, which has the added advantage of being able to differentiate PAHs with the same mass but different structure.9,10-Diphenylanthracene and triptycene, in addition to four different groups of PAH isomers: (1) anthracene and phenanthrene, (2) pyrene and fluoranthene, (3) benz[a]anthracene, benz[b]anthracene (tetracene), and chrysene (4) benzo[a]pyrene and benzo[k]fluoranthene, were deposited on a paper surface and bombarded with methanol droplets containing silver nitrate. The resulting microdroplets entered a quadruple mass spectrometer for mass analysis.The mass spectrum shows [PAH](+), [Ag + OH + PAH](+), and [Ag(PAH)(n)](+) (n = 1, 2) (and [PAH + O(2)](+) in the case of benz[b]anthracene) ions. PAHs having a bay structure, such as phenanthrene, showed a different tendency to interact with silver ions from those PAHs having a linear arrangement of the fused benzene rings, such as anthracene. The ratios of the [PAH](+) peak intensity to that of [Ag-PAH](+), [Ag + OH + PAH](+), [Ag(PAH)(2)](+), and [PAH + O(2)](+) were used to differentiate the PAH isomers sharing the same molecular formula with different structures. For isomeric mixtures the [PAH](+) to [Ag + OH + PAH](+) ratio was found to be the most useful parameter. The uncertainty in the mole fraction of an isomeric mixture was ±0.09, ±0.13, ±0.25, and ±0.1 for phenanthrene-anthracene, fluoranthene-pyrene, benz[a]anthracene-chrysene, and benzo[a]pyrene-benzo[k]fluoranthene, respectively.A simple method has been developed for the detection of PAHs in desorption electrospray ionization mass spectrometry based on Ag(I) cationization. The method showed a capability to differentiate PAHs isomers (having the same molecular mass) in isomeric mixture with an uncertainty in the mole fraction of about ±0.1. At high inlet temperature and voltage, this method showed better sensitivity but less ability to differentiate between isomeric species.

    View details for DOI 10.1002/rcm.6309

    View details for Web of Science ID 000306964600011

    View details for PubMedID 22847697

  • A Reduced Organic Carbon Component in Martian Basalts SCIENCE Steele, A., McCubbin, F. M., Fries, M., Kater, L., Boctor, N. Z., Fogel, M. L., Conrad, P. G., Glamoclija, M., Spencer, M., Morrow, A. L., Hammond, M. R., Zare, R. N., Vicenzi, E. P., Siljestrom, S., Bowden, R., Herd, C. D., Mysen, B. O., Shirey, S. B., Amundsen, H. E., Treiman, A. H., Bullock, E. S., Jull, A. J. 2012; 337 (6091): 212-215

    Abstract

    The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.

    View details for DOI 10.1126/science.1220715

    View details for Web of Science ID 000306323500053

    View details for PubMedID 22628557

  • Protein-inorganic hybrid nanoflowers NATURE NANOTECHNOLOGY Ge, J., Lei, J., Zare, R. N. 2012; 7 (7): 428-432

    Abstract

    Flower-shaped inorganic nanocrystals have been used for applications in catalysis and analytical science, but so far there have been no reports of 'nanoflowers' made of organic components. Here, we report a method for creating hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and various proteins as the organic component. The protein molecules form complexes with the copper ions, and these complexes become nucleation sites for primary crystals of copper phosphate. Interaction between the protein and copper ions then leads to the growth of micrometre-sized particles that have nanoscale features and that are shaped like flower petals. When an enzyme is used as the protein component of the hybrid nanoflower, it exhibits enhanced enzymatic activity and stability compared with the free enzyme. This is attributed to the high surface area and confinement of the enzymes in the nanoflowers.

    View details for DOI 10.1038/NNANO.2012.80

    View details for Web of Science ID 000306112000008

    View details for PubMedID 22659609

  • Advances in Asphaltene Science and the Yen-Mullins Model ENERGY & FUELS Mullins, O. C., Sabbah, H., Eyssautier, J., Pomerantz, A. E., Barre, L., Andrews, A. B., Ruiz-Morales, Y., Mostowfi, F., McFarlane, R., Goual, L., Lepkowicz, R., Cooper, T., Orbulescu, J., Leblanc, R. M., Edwards, J., Zare, R. N. 2012; 26 (7): 3986-4003

    View details for DOI 10.1021/ef300185p

    View details for Web of Science ID 000306503100004

  • Seemingly Anomalous Angular Distributions in H+D-2 Reactive Scattering SCIENCE Jankunas, J., Zare, R. N., Bouakline, F., Althorpe, S. C., Herraez-Aguilar, D., Aoiz, F. J. 2012; 336 (6089): 1687-1690

    Abstract

    When a hydrogen (H) atom approaches a deuterium (D(2)) molecule, the minimum-energy path is for the three nuclei to line up. Consequently, nearly collinear collisions cause HD reaction products to be backscattered with low rotational excitation, whereas more glancing collisions yield sideways-scattered HD products with higher rotational excitation. Here we report that measured cross sections for the H + D(2) → HD(v' = 4, j') + D reaction at a collision energy of 1.97 electron volts contradict this behavior. The anomalous angular distributions match closely fully quantum mechanical calculations, and for the most part quasiclassical trajectory calculations. As the energy available in product recoil is reduced, a rotational barrier to reaction cuts off contributions from glancing collisions, causing high-j' HD products to become backward scattered.

    View details for DOI 10.1126/science.1221329

    View details for Web of Science ID 000305794500045

    View details for PubMedID 22745425

  • Laser Desorption Single-Photon Ionization of Asphaltenes: Mass Range, Compound Sensitivity, and Matrix Effects ENERGY & FUELS Sabbah, H., Pomerantz, A. E., Wagner, M., Muellen, K., Zare, R. N. 2012; 26 (6): 3521-3526

    View details for DOI 10.1021/ef3002313

    View details for Web of Science ID 000305444400044

  • Chemical Recognition in Cell-Imprinted Polymers ACS NANO Ren, K., Zare, R. N. 2012; 6 (5): 4314-4318

    Abstract

    A glass slide covered with bacteria is pressed into another glass slide coated with partially cured polydimethylsiloxane (PDMS). The PDMS is hardened and the cells are removed to create a textured surface whose indentations preferentially capture the same type of bacteria when a mixture of bacteria is flowed over it. Overcoating the cell-imprinted PDMS with methylsilane groups causes the resulting surface to lose much of its ability to preferentially capture the imprinted bacteria, although the shapes of the imprints, measured by atomic force field microscopy, are shown to be hardly affected. We interpret this behavior as strong evidence that chemical recognition plays a dominant role in cell sorting with cell-imprinted PDMS polymer films.

    View details for DOI 10.1021/nn300901z

    View details for Web of Science ID 000304231700073

    View details for PubMedID 22468923

  • Surface-imprinted polymers in microfluidic devices SCIENCE CHINA-CHEMISTRY Schirhagl Romana, R., Ren Kangning, K. N., Zare Richard, N. 2012; 55 (4): 469-483

    View details for DOI 10.1007/s11426-012-4544-7

    View details for Web of Science ID 000303184300003

  • ANALYTICAL CHEMISTRY Ultrasensitive radiocarbon detection NATURE Zare, R. N. 2012; 482 (7385): 312-313

    View details for Web of Science ID 000300287100027

    View details for PubMedID 22337044

  • Transient Ru-methyl formate intermediates generated with bifunctional transfer hydrogenation catalysts PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Perry, R. H., Brownell, K. R., Chingin, K., Cahill, T. J., Waymouth, R. M., Zare, R. N. 2012; 109 (7): 2246-2250

    Abstract

    Desorption electrospray ionization (DESI) coupled to high-resolution Orbitrap mass spectrometry (MS) was used to study the reactivity of a (β-amino alcohol)(arene)RuCl transfer hydrogenation catalytic precursor in methanol (CH(3)OH). By placing [(p-cymene)RuCl(2)](2) on a surface and spraying a solution of β-amino alcohol in methanol, two unique transient intermediates having lifetimes in the submillisecond to millisecond range were detected. These intermediates were identified as Ru (II) and Ru (IV) complexes incorporating methyl formate (HCOOCH(3)). The Ru (IV) intermediate is not observed when the DESI spray solution is sparged with Ar gas, indicating that O(2) dissolved in the solvent is necessary for oxidizing Ru (II) to Ru (IV). These proposed intermediates are supported by high-resolution and high mass accuracy measurements and by comparing experimental to calculated isotope profiles. Additionally, analyzing the bulk reaction mixture using gas chromatography-MS and nuclear magnetic resonance spectroscopy confirms the formation of HCOOCH(3). These results represent an example that species generated from the (β-amino alcohol)(arene)RuCl (II) catalytic precursor can selectively oxidize CH(3)OH to HCOOCH(3). This observation leads us to propose a pathway that can compete with the hydrogen transfer catalytic cycle. Although bifunctional hydrogen transfer with Ru catalysts has been well-studied, the ability of DESI to intercept intermediates formed in the first few milliseconds of a chemical reaction allowed identification of previously unrecognized intermediates and reaction pathways in this catalytic system.

    View details for DOI 10.1073/pnas.1118934109

    View details for Web of Science ID 000300489200024

    View details for PubMedID 22315417

    View details for PubMedCentralID PMC3289342

  • Electrical, Optical, and Docking Properties of Conical Nanopores ACS NANO Li, Y., Zheng, Y., Zare, R. N. 2012; 6 (2): 993-997

    Abstract

    The diffusion-influenced translocation behavior of individual nanoparticles upon passage through a conical nanopore has been elucidated by using a pressure-reversal, resistive-pulse technique, as reported by Lan and White in this issue of ACS Nano. We outline here some recent progress in conical nanopore analysis, and we present some prospects for future developments. Compared to cylindrical nanopores, the geometric change brought about by tapered nanopores causes a dramatic difference in electrical and optical properties. Such conical nanopores may also be integrated into microfluidic chips to capture cells or nanoparticles, one per nanopore, and then to release them. These advances hold the promise of making conical nanopores useful as highly efficient actuators and sensors.

    View details for DOI 10.1021/nn300356d

    View details for Web of Science ID 000300757900001

    View details for PubMedID 22304827

  • Microfluidic capture and release of bacteria in a conical nanopore array LAB ON A CHIP Guo, P., Hall, E. W., Schirhagl, R., Mukaibo, H., Martin, C. R., Zare, R. N. 2012; 12 (3): 558-561

    Abstract

    We present a simple and inexpensive method for the capture and release of bacteria contained in an array of conical nanopores on a membrane inside a microfluidic device. As an example, we demonstrate that cyanobacteria can be captured, one bacterium per pore, in a defined orientation with over 500 bacteria per membrane with viabilities as high as 100%. The device can also specifically capture cyanobacteria from a mixed suspension of cyanobacteria and chlamydomonas with a selectivity as high as 90%.

    View details for DOI 10.1039/c2lc21092d

    View details for Web of Science ID 000298964300015

    View details for PubMedID 22170441

  • D+C(CH3)(4) -> HD (v ', j ')+C(CH3)(3)CH2: possible concerted flow of vibration energy into translation MOLECULAR PHYSICS Jankunas, J., Bartlett, N. C., Zare, R. N., Liu, L., Xu, X., Zhang, D. H. 2012; 110 (15-16): 1713-1720

    View details for DOI 10.1080/00268976.2012.673641

    View details for Web of Science ID 000307645400017

  • Reaction dynamics: concluding remarks FARADAY DISCUSSIONS Zare, R. N. 2012; 157: 501-504

    Abstract

    The 157th Faraday Discussion represented a historic turning point in the development of the field of reaction dynamics because it concerned itself with how reactions occur in gases, in liquid, and at interfaces. Never before has the attempt been made to unify the various approaches to reaction dynamics in one Faraday Discussion meeting and to discover what language was common and what was special to these previously distinct subdisciplines. This Discussion also marked a maturation of the field of reaction dynamics in that so much emphasis was placed on what the combination of theory and experiment could tell us about the detailed course of chemical transformations.

    View details for DOI 10.1039/c2fd20120h

    View details for Web of Science ID 000309137600028

    View details for PubMedID 23230784

  • Drug Release from Electric-Field-Responsive Nanoparticles ACS NANO Ge, J., Neofytou, E., Cahill, T. J., Beygui, R. E., Zare, R. N. 2012; 6 (1): 227-233

    Abstract

    We describe a new temperature and electric field dual-stimulus responsive nanoparticle system for programmed drug delivery. Nanoparticles of a conducting polymer (polypyrrole) are loaded with therapeutic pharmaceuticals and are subcutaneously localized in vivo with the assistance of a temperature-sensitive hydrogel (PLGA-PEG-PLGA). We have shown that drug release from the conductive nanoparticles is controlled by the application of a weak, external DC electric field. This approach represents a novel interactive drug delivery system that can show an externally tailored release profile with an excellent spatial, temporal, and dosage control.

    View details for DOI 10.1021/nn203430m

    View details for Web of Science ID 000299368300029

    View details for PubMedID 22111891

    View details for PubMedCentralID PMC3489921

  • H + D2 Reaction Dynamics in the Limit of the Low Product Recoil Energy J. Phys. Chem. Lett. Aldegunde, J., Aguilar, D. H., Jambrina, P. G., Aoiz, F. J., Jankunas, J., Zare, R. N. 2012; 3: 2959-2963
  • My Life with LIF: A Personal Account of Developing Laser-Induced Fluorescence ANNUAL REVIEW OF ANALYTICAL CHEMISTRY, VOL 5 Zare, R. N. 2012; 5: 1-14

    Abstract

    Laser-induced fluorescence (LIF) is a spectroscopic technique that involves the excitation of a molecular target by a beam of laser radiation followed by the detection of the subsequent emission of radiation from the target. LIF detection has several advantages over absorption spectroscopy. First, LIF has excellent detection sensitivity because a signal is observed against a dark background. Second, the emitted radiation can be collected at various angles with respect to the incoming laser beam, making it possible to obtain two- and three-dimensional images because the fluorescence is emitted in all directions. Third, by dispersing the fluorescence, it is also possible to learn about the transitions from the state excited to the various lower levels of the target species. Finally, because of the delay between the excitation and detection events, it is also possible to learn about what processes the excited target undergoes in the intervening time.

    View details for DOI 10.1146/annurev-anchem-062011-143148

    View details for Web of Science ID 000307956200002

    View details for PubMedID 22149473

  • Separation of bacteria with imprinted polymeric films ANALYST Schirhagl, R., Hall, E. W., Fuereder, I., Zare, R. N. 2012; 137 (6): 1495-1499

    Abstract

    Separation of compounds out of complex mixtures is a key issue that has been solved for small molecules by chromatography. However, general methods for the separation of large bio-particles, such as cells, are still challenging. We demonstrate integration of imprinted polymeric films (IPF) into a microfluidic chip, which preferentially capture cells matching an imprint template, and separate strains of cyanobacteria with 80-90% efficiency, despite a minimal difference in morphology and fluorescence, demonstrating its general nature. It is currently thought that the imprinting process, conducted while the polymer cures, transfers chemical information of the cell's external structure to the substrate. Capture specificity and separation can be further enhanced by orienting the imprints parallel to the flow vector and tuning the pH to a lower range.

    View details for DOI 10.1039/c2an15927a

    View details for Web of Science ID 000300510900030

    View details for PubMedID 22324051

  • In Vivo Sustained Release of siRNA from Solid Lipid Nanoparticles ACS NANO Lobovkina, T., Jacobson, G. B., Gonzalez-Gonzalez, E., Hickerson, R. P., Leake, D., Kaspar, R. L., Contag, C. H., Zare, R. N. 2011; 5 (12): 9977-9983

    Abstract

    Small interfering RNA (siRNA) is a highly potent drug in gene-based therapy with a challenge of being delivered in a sustained manner. Nanoparticle drug delivery systems allow for incorporating and controlled release of therapeutic payloads. We demonstrate that solid lipid nanoparticles can incorporate and provide sustained release of siRNA. Tristearin solid lipid nanoparticles, made by nanoprecipitation, were loaded with siRNA (4.4-5.5 wt % loading ratio) using a hydrophobic ion pairing approach that employs the cationic lipid DOTAP. Intradermal injection of these nanocarriers in mouse footpads resulted in prolonged siRNA release over a period of 10-13 days. In vitro cell studies showed that the released siRNA retained its activity. Nanoparticles developed in this study offer an alternative approach to polymeric nanoparticles for encapsulation and sustained delivery of siRNA with the advantage of being prepared from physiologically well-tolerated materials.

    View details for DOI 10.1021/nn203745n

    View details for Web of Science ID 000298316700073

    View details for PubMedID 22077198

    View details for PubMedCentralID PMC3246574

  • Can stimulated Raman pumping cause large population transfers in isolated molecules? JOURNAL OF CHEMICAL PHYSICS Mukherjee, N., Zare, R. N. 2011; 135 (18)

    Abstract

    When stimulated Raman pumping (SRP) is applied to a stream of isolated molecules, such as found in a supersonic molecular beam expansion, we show that SRP can neither saturate nor power broaden a molecular transition connecting two metastable levels that is resonant with the energy difference between the pump and Stokes laser pulses. Using the optical Bloch-Feynman equations, we discuss the pumping of the hydrogen molecule from H(2) (v = 0, J = 0, M = 0) to H(2) (v = 1, J = 2, M = 0) as an illustration of how coherent population return severely reduces the SRP pumping efficiency unless the pump and Stokes laser pulses are applied with an appropriate relative delay and ratio of intensities.

    View details for DOI 10.1063/1.3657832

    View details for Web of Science ID 000297472800016

    View details for PubMedID 22088058

  • Glucose-Driven Fuel Cell Constructed from Enzymes and Filter Paper JOURNAL OF CHEMICAL EDUCATION Ge, J., Schirhagl, R., Zare, R. N. 2011; 88 (9): 1283-1286

    View details for DOI 10.1021/ed100967j

    View details for Web of Science ID 000293813100021

  • Stark-induced adiabatic Raman passage for preparing polarized molecules JOURNAL OF CHEMICAL PHYSICS Mukherjee, N., Zare, R. N. 2011; 135 (2)

    Abstract

    We propose a method based on Stark-induced adiabatic Raman passage (SARP) for preparing vibrationally excited molecules with known orientation and alignment for future dynamical stereochemistry studies. This method utilizes the (J, M)-state dependent dynamic Stark shifts of rovibrational levels induced by delayed but overlapping pump and Stokes pulses of unequal intensities. Under collision-free conditions, our calculations show that we can achieve complete population transfer to an excited vibrational level (v > 0) of the H(2) molecule in its ground electronic state. Specifically, the H(2) (v = 1, J = 2, M = 0) level can be prepared with complete population transfer from the (v = 0, J = 0, M = 0) level using the S(0) branch of the Raman transition with visible pump and Stoke laser pulses, each polarized parallel to the z axis (uniaxial π-π Raman pumping). Similarly, H(2) (v = 1, J = 2, M = ±2) can be prepared using SARP with a left circularly polarized pump and a right circularly (or vice versa) polarized Stokes wave propagating along the z axis (σ(±)-σ(∓) Raman pumping). This technique requires phase coherent nanosecond pulses with unequal intensity between the pump and the Stokes pulses, one being four or more times greater than the other. A peak intensity of ~16 GW/cm(2) for the stronger pulse is required to generate the desirable sweep of the Raman resonance frequency. These conditions may be fulfilled using red and green laser pulses with the duration of a few nanoseconds and optical energies of ~12 and 60 mJ within a focused beam of diameter ~0.25 mm. Additionally, complete population transfer to the v = 4 vibrational level is predicted to be possible using SARP with a 355-nm pump and a near infrared Stokes laser with accessible pulse energies.

    View details for DOI 10.1063/1.3599711

    View details for Web of Science ID 000292776000017

    View details for PubMedID 21766932

  • False estimates of stimulated Raman pumping efficiency caused by the optical Stark effect JOURNAL OF CHEMICAL PHYSICS Bartlett, N. M., Jankunas, J., Zare, R. N. 2011; 134 (23)

    Abstract

    One technique for measuring the fraction of molecules pumped to the excited state in stimulated Raman pumping (SRP) is to record the depletion of molecules in the lower state by resonance enhanced multiphoton ionization (REMPI). The presence of electric fields on the order of 10(7) V/cm arising from the pulsed SRP laser beams is sufficient to shift the line position of the REMPI transition to such an extent that the estimate of the pumping efficiency is overestimated unless this shift is accounted for.

    View details for DOI 10.1063/1.3601923

    View details for Web of Science ID 000291992500019

    View details for PubMedID 21702559

  • Bovine Serum Albumin-Poly(methyl methacrylate) Nanoparticles: An Example of Frustrated Phase Separation NANO LETTERS Ge, J., Lei, J., Zare, R. N. 2011; 11 (6): 2551-2554

    Abstract

    A new protein-polymer conjugate made of denatured bovine serum albumin (BSA) covalently bonded to poly(methyl methacrylate) (PMMA) is synthesized by attaching PMMA to acryloylated BSA followed by nanoparticle precipitation. Depending on the BSA to PMMA ratio, these conjugates self-assemble into uniform spherical nanoparticles which show "island" growth on the surface of the nanoparticles. This growth is promoted or retarded by exposing the nanoparticles to different solvents, causing the two components to undergo incipient phase separation. Incipient phase separation of the BSA-PMMA conjugate two-component system was observed in single nanoparticles, resulting in "island" growth on the surface of the nanoparticles. Incipient phase separation of the BSA-PMMA conjugate two-component system was observed in single nanoparticles, resulting in "island" growth on the surface of the nanoparticles.

    View details for DOI 10.1021/nl201303q

    View details for Web of Science ID 000291322600062

    View details for PubMedID 21553851

  • Nanoparticle PEGylation for imaging and therapy NANOMEDICINE Jokerst, J. V., Lobovkina, T., Zare, R. N., Gambhir, S. S. 2011; 6 (4): 715-728

    Abstract

    Nanoparticles are an essential component in the emerging field of nanomedical imaging and therapy. When deployed in vivo, these materials are typically protected from the immune system by polyethylene glycol (PEG). A wide variety of strategies to coat and characterize nanoparticles with PEG has established important trends on PEG size, shape, density, loading level, molecular weight, charge and purification. Strategies to incorporate targeting ligands are also prevalent. This article presents a background to investigators new to stealth nanoparticles, and suggests some key considerations needed prior to designing a nanoparticle PEGylation protocol and characterizing the performance features of the product.

    View details for DOI 10.2217/NNM.11.19

    View details for Web of Science ID 000292994300019

    View details for PubMedID 21718180

    View details for PubMedCentralID PMC3217316

  • Evidence for Island Structures as the Dominant Architecture of Asphaltenes ENERGY & FUELS Sabbah, H., Morrow, A. L., Pomerantz, A. E., Zare, R. N. 2011; 25 (4): 1597-1604

    View details for DOI 10.1021/ef101522w

    View details for Web of Science ID 000289697700030

  • Whole gene amplification and protein separation from a few cells ANALYTICAL BIOCHEMISTRY Chueh, B., Li, C., Wu, H., Davison, M., Wei, H., Bhaya, D., Zare, R. N. 2011; 411 (1): 64-70

    Abstract

    Despite the growing interest to explore untapped microbial gene and protein diversity, no single platform has been able to acquire both gene and protein information from just a few cells. We present a microfluidic system that simultaneously performs on-chip capillary electrophoresis for protein analysis and whole genome amplification (WGA), and we demonstrate this by doing both for the same cohort of cyanobacterial cells. This technology opens avenues for studying protein profiles of precious environmental microbial samples and simultaneously accessing genomic information based on WGA.

    View details for DOI 10.1016/j.ab.2010.12.028

    View details for Web of Science ID 000287618900009

    View details for PubMedID 21185803

  • Interfacing Capillary-Based Separations to Mass Spectrometry Using Desorption Electrospray Ionization ANALYTICAL CHEMISTRY Barbula, G. K., Safi, S., Chingin, K., Perry, R. H., Zare, R. N. 2011; 83 (6): 1955-1959

    Abstract

    The powerful hybrid analysis method of capillary-based separations followed by mass spectrometric analysis gives substantial chemical identity and structural information. It is usually carried out using electrospray ionization. However, the salts and detergents used in the mobile phase for electrokinetic separations suppress ionization efficiencies and contaminate the inlet of the mass spectrometer. This report describes a new method that uses desorption electrospray ionization (DESI) to overcome these limitations. Effluent from capillary columns is deposited on a rotating Teflon disk that is covered with paper. As the surface rotates, the temporal separation of the eluting analytes (i.e., the electropherogram) is spatially encoded on the surface. Then, using DESI, surface-deposited analytes are preferentially ionized, reducing the effects of ion suppression and inlet contamination on signal. With the use of this novel approach, two capillary-based separations were performed: a mixture of the rhodamine dyes at milligram/milliliter levels in a 10 mM sodium borate solution was separated by capillary electrophoresis, and a mixture of three cardiac drugs at milligram/milliliter levels in a 12.5 mM sodium borate and 12.5 mM sodium dodecyl sulfate solution was separated by micellar electrokinetic chromatography. In both experiments, the negative effects of detergents and salts on the MS analyses were minimized.

    View details for DOI 10.1021/ac102648k

    View details for Web of Science ID 000288182900014

    View details for PubMedID 21319740

  • Preparation of Mineralized Nanofibers: Collagen Fibrils Containing Calcium Phosphate NANO LETTERS Maas, M., Guo, P., Keeney, M., Yang, F., Hsu, T. M., Fuller, G. G., Martin, C. R., Zare, R. N. 2011; 11 (3): 1383-1388

    Abstract

    We report a straightforward, bottom-up, scalable process for preparing mineralized nanofibers. Our procedure is based on flowing feed solution, containing both inorganic cations and polymeric molecules, through a nanoporous membrane into a receiver solution with anions, which leads to the formation of mineralized nanofibers at the exit of the pores. With this strategy, we were able to achieve size control of the nanofiber diameters. We illustrate this approach by producing collagen fibrils with calcium phosphate incorporated inside the fibrils. This structure, which resembles the basic constituent of bones, assembles itself without the addition of noncollagenous proteins or their polymeric substitutes. Rheological experiments demonstrated that the stiffness of gels derived from these fibrils is enhanced by mineralization. Growth experiments of human adipose derived stem cells on these gels showed the compatibility of the fibrils in a tissue-regeneration context.

    View details for DOI 10.1021/nl200116d

    View details for Web of Science ID 000288061500082

    View details for PubMedID 21280646

    View details for PubMedCentralID PMC3053435

  • Particle sorting using a porous membrane in a microfluidic device LAB ON A CHIP Wei, H., Chueh, B., Wu, H., Hall, E. W., Li, C., Schirhagl, R., Lin, J., Zare, R. N. 2011; 11 (2): 238-245

    Abstract

    Porous membranes have been fabricated based on the development of the perforated membrane mold [Y. Luo and R. N. Zare, Lab Chip, 2008, 8, 1688-1694] to create a single filter that contains multiple pore sizes ranging from 6.4 to 16.6 µm inside a monolithic three-dimensional poly(dimethylsiloxane) microfluidic structure. By overlapping two filters we are able to achieve smaller pore size openings (2.5 to 3.3 µm). This filter operates without any detectable irreversible clogging, which is achieved using a cross-flow placed in front of each filtration section. The utility of a particle-sorting device that contains this filter is demonstrated by separating polystyrene beads of different diameters with an efficiency greater than 99.9%. Additionally, we demonstrate the effectiveness of this particle-sorting device by separating whole blood samples into white blood cells and red blood cells with platelets.

    View details for DOI 10.1039/c0lc00121j

    View details for Web of Science ID 000285514700007

    View details for PubMedID 21057685

  • Microfluidic purification and analysis of hematopoietic stem cells from bone marrow LAB ON A CHIP Schirhagl, R., Fuereder, I., Hall, E. W., Medeiros, B. C., Zare, R. N. 2011; 11 (18): 3130-3135

    Abstract

    Hematopoietic stem cells are larger in size than other cells present in bone marrow, with the exception of monocytes. This distinguishing characteristic can be used to separate them from a whole-marrow sample. A microfluidic device was fabricated using an integrated membrane that is porous at defined areas. This allows for simultaneous valving and filtering functionality, which is crucial for preventing irreversible clogging. This device, as well as a separation procedure, was optimized in this work to enrich hematopoietic progenitor cells from diluted bone marrow of leukemia patients without any additional sample preparation. An enrichment of up to 98% was achieved with this method and the process was scaled up to 17.2 μL min(-1) of processed sample. Additionally, stem cells were stained with specific antibodies for further analysis. Using a custom-made computer program, the filter was scanned to characterize and quantify cells based on fluorescence. The results were evaluated by comparing them against the results obtained from flow cytometry, confocal microscopy, and Coulter counting.

    View details for DOI 10.1039/c1lc20353c

    View details for Web of Science ID 000294263400013

    View details for PubMedID 21799976

  • Detecting Reaction Intermediates in Liquids on the Millisecond Time Scale Using Desorption Electrospray Ionization Angew. Chemie Int. Ed. Perry, R. H., Splendore, M., Chien, A., Davis, N. K., Zare, R. N. 2011; 50: 250-254
  • Control and imaging of O(D-1(2)) precession NATURE CHEMISTRY Wu, S., Radenovic, D. C., van der Zande, W. J., Groenenboom, G. C., Parker, D. H., Vallance, C., Zare, R. N. 2011; 3 (1): 28-33

    Abstract

    Larmor precession of a quantum mechanical angular momentum vector about an applied magnetic field forms the basis for a range of magnetic resonance techniques, including nuclear magnetic resonance spectroscopy and magnetic resonance imaging. We have used a polarized laser pump-probe scheme with velocity-map imaging detection to visualize, for the first time, the precessional motion of a quantum mechanical angular momentum vector. Photodissociation of O(2) at 157 nm provides a clean source of fast-moving O((1)D(2)) atoms, with their electronic angular momentum vector strongly aligned perpendicular to the recoil direction. In the presence of an external magnetic field, the distribution of atomic angular momenta precesses about the field direction, and polarization-sensitive images of the atomic scattering distribution recorded as a function of field strength yield 'time-lapse-photography' style movies of the precessional motion. We present movies recorded in various experimental geometries, and discuss potential consequences and applications in atmospheric chemistry and reaction dynamics.

    View details for DOI 10.1038/NCHEM.929

    View details for Web of Science ID 000285336900012

    View details for PubMedID 21160513

  • Generation of Melamine Polymer Condensates upon Hypergolic Ignition of Dicyanamide Ionic Liquids ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Chingin, K., Perry, R. H., Chambreau, S. D., Vaghjiani, G. L., Zare, R. N. 2011; 50 (37): 8634-8637

    View details for DOI 10.1002/anie.201101247

    View details for Web of Science ID 000295261200034

    View details for PubMedID 21786369

  • Differential cross sections for H + D-2 -> HD(v '=2, j '=0,3,6,9) + D at center-of-mass collision energies of 1.25, 1.61, and 1.97 eV PHYSICAL CHEMISTRY CHEMICAL PHYSICS Bartlett, N. C., Jankunas, J., Goswami, T., Zare, R. N., Bouakline, F., Althorpe, S. C. 2011; 13 (18): 8175-8179

    Abstract

    We have measured differential cross sections (DCSs) for the reaction H + D(2) → HD(v' = 2,j' = 0,3,6,9) + D at center-of-mass collision energies E(coll) of 1.25, 1.61, and 1.97 eV using the photoloc technique. The DCSs show a strong dependence on the product rotational quantum number. For the HD(v' = 2,j' = 0) product, the DCS is bimodal but becomes oscillatory as the collision energy is increased. For the other product states, they are dominated by a single peak, which shifts from back to sideward scattering as j' increases, and they are in general less sensitive to changes in the collision energy. The experimental results are compared to quantum mechanical calculations and show good, but not fully quantitative agreement.

    View details for DOI 10.1039/c0cp02460k

    View details for Web of Science ID 000289954300012

    View details for PubMedID 21170442

  • Detecting Reaction Intermediates in Liquids on the Millisecond Time Scale Using Desorption Electrospray Ionization ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Perry, R. H., Splendore, M., Chien, A., Davis, N. K., Zare, R. N. 2011; 50 (1): 250-254

    View details for DOI 10.1002/anie.201004861

    View details for Web of Science ID 000285891900019

    View details for PubMedID 21110361

  • Stopped-Flow Kinetic Analysis Using Hadamard Transform Time-of-Flight Mass Spectrometry ANALYTICAL CHEMISTRY Robbins, M. D., Yoon, O. K., Barbula, G. K., Zare, R. N. 2010; 82 (20): 8650-8657

    Abstract

    A home-built stopped-flow apparatus is interfaced to a Hadamard transform time-of-flight mass spectrometer, which permits study of reaction kinetics with a time between reaction initiation and observation as short as about 100 ms and a sampling rate of chemical change that can approach 1 ms. This technique is applied to the trypsin-catalyzed hydrolysis of several peptides and is validated by comparing the results with literature values as well as to optical data obtained with the present stopped-flow apparatus. In addition, we report a kinetic study of the action of trypsin on a peptide having more than one cleavage site.

    View details for DOI 10.1021/ac101899n

    View details for Web of Science ID 000282859100040

    View details for PubMedID 20843011

  • Polycyclic aromatic hydrocarbons in asteroid 2008 TC3: Dispersion of organic compounds inside asteroids METEORITICS & PLANETARY SCIENCE Sabbah, H., Morrow, A. L., Jenniskens, P., Shaddad, M. H., Zare, R. N. 2010; 45 (10-11): 1710-1717

    View details for DOI 10.1111/j.1945-5100.2010.01103.x

    View details for Web of Science ID 000285759700009

  • Biodegradable Nanoparticles With Sustained Release of Functional siRNA in Skin JOURNAL OF PHARMACEUTICAL SCIENCES Jacobson, G. B., Gonzalez-Gonzalez, E., Spitler, R., Shinde, R., Leake, D., Kaspar, R. L., Contag, C. H., Zare, R. N. 2010; 99 (10): 4261-4266

    Abstract

    A key challenge in developing RNAi-based therapeutics is efficient delivery of functional short interfering RNA (siRNA) to target cells. To address this need, we have used a supercritical CO(2) process to incorporate siRNA in biodegradable polymer nanoparticles (NPs) for in vivo sustained release. By this means we have obtained complete encapsulation of the siRNA with minimal initial burst effect from the surface of the NPs. The slow release of a fluorescently labeled siRNA mimic (siGLO Red) was observed for up to 80 days in vivo after intradermal injection into mouse footpads. In vivo gene silencing experiments were also performed, showing reduction of GFP signal in the epidermis of a reporter transgenic mouse model, which demonstrates that the siRNA retained activity following release from the polymer NPs.

    View details for DOI 10.1002/jps.22147

    View details for Web of Science ID 000282473400012

    View details for PubMedID 20737633

  • Polarization of molecular targets using infrared stimulated Raman adiabatic passage JOURNAL OF CHEMICAL PHYSICS Mukherjee, N., Zare, R. N. 2010; 133 (9)

    Abstract

    We suggest that infrared stimulated Raman adiabatic passage, a coherent multiple excitation process, can be used to create a superposition of (2J+1) highly correlated M-state sublevels of a rigid rotor molecule with vibrational level v and rotational level J. This method employs the (v=0,J-2) to (v=2,J) S-branch transition, which is carried out in a counterintuitive manner in which the v=1 to v=2 transition is pumped prior to the v=0 to v=1 transition, causing nearly complete population transfer to the v=2 final level. We use perpendicular and parallel linearly polarized infrared excitation (biaxial excitation). Specifically, the perpendicular polarization connects the v=1 intermediate level to the final vibrational level v=2, and the parallel polarization connects the initial level v=0 to the intermediate level v=1. By this means we break the cylindrical symmetry for an ensemble of vibrationally excited molecules in a rovibrational eigenstate (v=2,J). The angular momentum polarization is determined by the relative phases rather than by the populations of the magnetic M-sublevels. For the phase correlated ensemble, the angular momentum polarization can be considered as a purely quantum mechanical effect. Using a fully general density matrix treatment, we illustrate this approach by considering a beam of carbon monoxide (CO) molecules. We find that significant polarization for J=2, 5, and 10 can be achieved with a cw infrared laser source having modest power (∼100 mW/mm(2)). We believe that this technique is a general one and may offer an experimentally accessible new platform for different applications, from scattering studies with M-state entangled ensembles of molecules to logic gate operations of a quantum computer.

    View details for DOI 10.1063/1.3475523

    View details for Web of Science ID 000281742900007

    View details for PubMedID 20831312

  • Comparing Laser Desorption/Laser Ionization Mass Spectra of Asphaltenes and Model Compounds ENERGY & FUELS Sabbah, H., Morrow, A. L., Pomerantz, A. E., Mullins, O. C., Tan, X., Gray, M. R., Azyat, K., Tykwinski, R. R., Zare, R. N. 2010; 24: 3589-3594

    View details for DOI 10.1021/ef100402g

    View details for Web of Science ID 000278851200041

  • General Method for Producing Organic Nanoparticles Using Nanoporous Membranes NANO LETTERS Guo, P., Martin, C. R., Zhao, Y., Ge, J., Zare, R. N. 2010; 10 (6): 2202-2206

    Abstract

    Two liquids are separated by a nanoporous membrane and one liquid is made to flow into the other, causing nanoparticles to be formed at the exits of the nanopores. In particular, we report the generation of nanoparticles of the biodegradable polysaccharide polymer chitosan by placing the chitosan in a low pH aqueous solution that is flowed into a high pH aqueous solution. The size of the nanoparticles (5-20 nm) can be roughly controlled by choosing the size of the nanopores and the pumping rate. In addition, it is possible to load the chitosan nanoparticles with drug molecules, which is demonstrated by incorporation of up to 3.3% rhodamine 6G molecules in the chitosan nanoparticles.

    View details for DOI 10.1021/nl101057d

    View details for Web of Science ID 000278449200039

    View details for PubMedID 20441186

  • Nanoparticle Formation of Organic Compounds With Retained Biological Activity JOURNAL OF PHARMACEUTICAL SCIENCES Jacobson, G. B., Shinde, R., McCullough, R. L., Cheng, N. J., Creasman, A., Beyene, A., Hickerson, R. P., Quan, C., Turner, C., Kaspar, R. L., Contag, C. H., Zare, R. N. 2010; 99 (6): 2750-2755

    Abstract

    Many pharmaceuticals are formulated as powders to aid drug delivery. A major problem is how to produce powders having high purity, controlled morphology, and retained bioactivity. We demonstrate the use of supercritical carbon dioxide as an antisolvent for meeting this need for two model drug systems, quercetin, a sparingly soluble antioxidant, and short interfering RNA (siRNA), which can silence genes. In both cases we achieve retention of bioactivity as well as a narrow particle size distribution in which the particles are free of impurities.

    View details for DOI 10.1002/jps.22035

    View details for Web of Science ID 000278241800022

    View details for PubMedID 20039390

  • Preparation of polarized molecules using coherent infrared multicolor ladder excitation JOURNAL OF CHEMICAL PHYSICS Mukherjee, N., Zare, R. N. 2010; 132 (15)

    Abstract

    A density matrix treatment is presented for a general process of preparing polarized molecules through their coherent interaction with two or more infrared photons of different frequencies, each tuned to cause a transition between real levels. This process, which might be called infrared stimulated Raman adiabatic passage, allows complete population transfer to selected rotational-vibrational levels and controls the direction of the rotational angular momentum vector J of the molecule with the possibility of preparing higher moments of the J spatial distribution. HCl molecules in a supersonic molecular beam are considered as a candidate system. Theory predicts that under collision-free conditions two infrared laser pulses of microsecond duration and milliwatt power are able to achieve complete population transfer and alignment of HCl (v=2, J=2, and M=0) for mutually parallel excitation and HCl (v=2, J=2, and M=+/-1) for mutually perpendicular excitation. Orientation of the HCl (v=2, J=2, and M=+/-2) can also be achieved using two circularly polarized pulses of the same helicity. For simplicity, our treatment ignores nuclear spin depolarization, which would be the case for molecules such as (12)C(16)O and (12)C(16)OO(2). Polarized molecules in higher vibrational levels can be prepared using additional infrared pulses.

    View details for DOI 10.1063/1.3352553

    View details for Web of Science ID 000276971500016

    View details for PubMedID 20423176

  • Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2 METEORITICS & PLANETARY SCIENCE Sandford, S. A., Bajt, S., Clemett, S. J., Cody, G. D., Cooper, G., Degregorio, B. T., de Vera, V., Dworkin, J. P., Elsila, J. E., Flynn, G. J., Glavin, D. P., Lanzirotti, A., Limero, T., Martin, M. P., Snead, C. J., Spencer, M. K., Stephan, T., Westphal, A., Wirick, S., Zare, R. N., Zolensky, M. E. 2010; 45 (3): 406-433

    View details for DOI 10.1111/j.1945-5100.2010.01031.x

    View details for Web of Science ID 000279904700006

  • Search for Br* production in the D plus DBr reaction JOURNAL OF CHEMICAL PHYSICS Zhang, J., Jankunas, J., Bartlett, N. C., Goldberg, N. T., Zare, R. N. 2010; 132 (8)

    Abstract

    Deuterium bromide (DBr) is expanded from a pulsed jet into a vacuum and a synchronized pulsed laser causes photodissociation of some of the DBr molecules to produce primarily (approximately 85%) ground-state bromine atoms ((2)P(3/2)) and fast D atoms. The latter collide with the cold DBr molecules and react to produce molecular deuterium (D(2)) via two possible channels, the adiabatic channel D(2)+Br((2)P(3/2)) and the nonadiabatic channel D(2)+Br*((2)P(1/2)), which are asymptotically separated in energy by the spin-orbit splitting (0.457 eV) of the bromine atom. Ion images are recorded for D(2)(v'=1, J'=16, 18-21), D(2)(v'=2, J'=6,7, 10-12, 14-16), and D(2)(v'=3, J'=2-5) for various collision energies. For the nonadiabatic production of spin-orbit-excited Br* in the D+DBr reaction for the conditions studied we estimate that this channel contributes 1% or less.

    View details for DOI 10.1063/1.3319717

    View details for Web of Science ID 000275029200016

    View details for PubMedID 20192296

  • Search for Br* Production in the D + DBr Reaction J. Chem. Phys. Zhang, J., Jankunas, J., Bartlett, N. C., Goldberg, N. T., Zare, R. N. 2010; 132: 084301-1-7
  • SINGLE-MOLECULE SPECTROSCOPY USING MICROFLUIDIC PLATFORMS METHODS IN ENZYMOLOGY, VOL 472: SINGLE MOLECULE TOOLS, PT A: FLUORESCENCE BASED APPROACHES Kim, S., Zare, R. N. 2010; 472: 119-132

    Abstract

    Microfluidics serves as a convenient platform for single-molecule experiments by providing manipulation of small amounts of liquids and micron-sized particles. An adapted version of capillary electrophoresis (CE) on a microchip can be utilized to separate chemical species with high resolution based on their ionic mobilities (i.e., charges and sizes), but identification of separated species is not trivial, especially for complex mixtures of sticky biomolecules. We describe here how to use a surfactant mixture system for CE on a poly(dimethylsiloxane) (PDMS) microchip, capture separated peaks within a 50-pl chamber using microvalves, analyze the fluorescence signals with correlation spectroscopy to extract molecular diffusion characteristics, and to identify the biomolecular clusters in a model immunocomplex system.

    View details for DOI 10.1016/S0076-6879(10)72013-9

    View details for Web of Science ID 000279058600007

    View details for PubMedID 20580962

  • Sustained release of nucleic acids from polymeric nanoparticles using microemulsion precipitation in supercritical carbon dioxide CHEMICAL COMMUNICATIONS Ge, J., Jacobson, G. B., Lobovkina, T., Holmberg, K., Zare, R. N. 2010; 46 (47): 9034-9036

    Abstract

    A general approach for producing biodegradable nanoparticles for sustained nucleic acid release is presented. The nanoparticles are produced by precipitating a water-in-oil microemulsion in supercritical CO(2). The microemulsion consists of a transfer RNA aqueous solution (water phase), dichloromethane containing poly(l-lactic acid)-poly(ethylene glycol) (oil phase), the surfactant n-octyl β-D-glucopyranoside, and the cosurfactant n-butanol.

    View details for DOI 10.1039/c0cc04258g

    View details for Web of Science ID 000284482100040

    View details for PubMedID 21052588

  • Microfluidic Platforms for Single-Cell Analysis ANNUAL REVIEW OF BIOMEDICAL ENGINEERING, VOL 12 Zare, R. N., Kim, S. 2010; 12: 187-201

    Abstract

    Microfluidics, the study and control of the fluidic behavior in microstructures, has emerged as an important enabling tool for single-cell chemical analysis. The complex procedures for chemical cytometry experiments can be integrated into a single microfabricated device. The capability of handling a volume of liquid as small as picoliters can be utilized to manipulate cells, perform controlled cell lysis and chemical reactions, and efficiently minimize sample dilution after lysis. The separation modalities such as chromatography and electrophoresis within microchannels are incorporated to analyze various types of intracellular components quantitatively. The microfluidic approach offers a rapid, accurate, and cost-effective tool for single-cell biology. We present an overview of the recent developments in microfluidic technology for chemical-content analysis of individual cells.

    View details for DOI 10.1146/annurev-bioeng-070909-105238

    View details for Web of Science ID 000281447400008

    View details for PubMedID 20433347

  • Time-dependent depolarization of aligned D-2 caused by hyperfine coupling PHYSICAL CHEMISTRY CHEMICAL PHYSICS Bartlett, N. C., Jankunas, J., Zare, R. N., Harrison, J. A. 2010; 12 (48): 15689-15694

    Abstract

    Molecular deuterium is prepared in the J = 2, M = 0 sublevel of ν = 1 by stimulated Raman pumping of the ν = 0 S(0) line. Following optical excitation, the degree of alignment of the rotational angular momentum J oscillates in time caused by the coupling of J to the total nuclear spin angular momentum I(T). This coupling is of two kinds, the interaction of J with the magnetic moments and the quadrupole fields of the two I = 1 deuterium nuclei. The alignment is monitored via the O(2) line of the E,F(1)Σ(g)(+)-X(1)Σ(g)(+) (0,1) band using [2+1] resonance enhanced multiphoton ionization for pump-probe delays from 0 to 20 μs. Using the hyperfine coupling constants found previously for the ν = 0 state (R. F. Code and N. F. Ramsey, Phys. Rev. A, 1971, 4, 1945), we are able to fit the time dependence essentially within our experimental error, but this requires that the presence of both I(T) = 0 and I(T) = 2 nuclear spin states for this o-deuterium level is properly weighted and taken into account.

    View details for DOI 10.1039/c0cp00518e

    View details for Web of Science ID 000284776700015

    View details for PubMedID 20668756

  • Desorption Electrospray Ionization: Achieving Rapid Sampling Rates ANALYTICAL CHEMISTRY Barbula, G. K., Robbins, M. D., Yoon, O. K., Zuleta, I., Zare, R. N. 2009; 81 (21): 9035-9040

    Abstract

    The sampling rate and imaging capabilities of desorption electrospray ionization (DESI) are examined using a rotating sample platform combined with Hadamard transform time-of-flight mass spectrometry (HTTOFMS), a multiplexed time-of-flight technique that allows for millisecond acquisition of full mass-to-charge ratio scans. DESI-compatible dyes are used to produce spatially defined sample patterns on poly(methyl methacrylate) discs. Control of disk rotation rate sets the residence time of the sample spots in the DESI plume, and thus the sampling rate. Surface patterns of alternating analytes are spectrally resolved up to 80 samples/s and single-analyte spots up to 50 samples/s. The rapid movement of the surface under the DESI plume allows for high DESI solution flow rates without blurring the chemical information on the surface. Data from multiple rotations can be additively combined, generating a chemical image of the surface with improved signal-to-noise characteristics. This multipass data enables analysis of the rising and falling edges of the analyte signal, placing a lower limit on both the temporal resolution of DESI and the maximum achievable sampling rate. Multipass analysis is proposed as a method for DESI surface imaging.

    View details for DOI 10.1021/ac901668a

    View details for Web of Science ID 000276191900054

    View details for PubMedID 19778033

  • High-precision optical measurements of C-13/C-12 isotope ratios in organic compounds at natural abundance PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Zare, R. N., Kuramoto, D. S., Haase, C., Tan, S. M., Crosson, E. R., Saad, N. M. 2009; 106 (27): 10928-10932

    Abstract

    A continuous-flow cavity ring-down spectroscopy (CRDS) system integrating a chromatographic separation technique, a catalytic combustor, and an isotopic (13)C/(12)C optical analyzer is described for the isotopic analysis of a mixture of organic compounds. A demonstration of its potential is made for the geochemically important class of short-chain hydrocarbons. The system proved to be linear over a 3-fold injection volume dynamic range with an average precision of 0.95 per thousand and 0.67 per thousand for ethane and propane, respectively. The calibrated accuracy for methane, ethane, and propane is within 3 per thousand of the values determined using isotope ratio mass spectrometry (IRMS), which is the current method of choice for compound-specific isotope analysis. With anticipated improvements, the low-cost, portable, and easy-to-use CRDS-based instrumental setup is poised to evolve into a credible challenge to the high-cost and complex IRMS-based technique.

    View details for DOI 10.1073/pnas.0904230106

    View details for Web of Science ID 000267796100013

    View details for PubMedID 19564619

    View details for PubMedCentralID PMC2708708

  • Ultraviolet thermal lensing detection of amino acids 32nd International Symposium on High Performance Liquid Phase Separations and Related Techniques Yu, F., Kachanov, A. A., Koulikov, S., Wainright, A., Zare, R. N. ELSEVIER SCIENCE BV. 2009: 3423–30

    Abstract

    Thermal lensing (TL) permits ultra-sensitive measurements of optical absorption of analytes in very small liquid volumes. We report the construction and use of a TL detector based on pulsed ultraviolet (UV) laser excitation (266 nm). We applied this detector to quantitate amino acids using capillary electrophoresis (CE) as a means of separation. Sixteen individual amino acids are readily detected, but the signal has a complex dependence on intensity caused by the combination of (1) one-photon absorption; (2) two-photon absorption (TPA); and (3) photodestruction of amino acid molecules in the focus of the laser beam. An aqueous solution containing tyrosine, tryptophan, and cysteine is electrophoretically separated and the individual amino acids are detected by UV TL. The estimated limit of detection is 7 microM for tyrosine, 2.5 microM for tryptophan and 33 microM for cysterine, which translates into 0.35 fmol for tyrosine, 0.125 fmol for tryptophan, and 1.65 fmol for cysteine in the 140pL detection volume. It is found that two-photon absorption of water and the formation of color centers in the fused silica walls of the flowcell can contribute a significant, drifting background signal, but this interference can be minimized by selecting an appropriate focus condition and excitation-detection geometry. We suggest that as UV laser sources become available, UV TL may become a method of choice for measuring the concentrations of many analytes in different separation formats in which the volume is highly limited.

    View details for DOI 10.1016/j.chroma.2008.05.096

    View details for Web of Science ID 000265262300002

    View details for PubMedID 18589430

  • Asphaltene Molecular-Mass Distribution Determined by Two-Step Laser Mass Spectrometry 9th International Conference on Petroleum Phase Behavior and Fouling Pomerantz, A. E., Hammond, M. R., Morrow, A. L., Mullins, O. C., Zare, R. N. AMER CHEMICAL SOC. 2009: 1162–1168

    View details for DOI 10.1021/ef8006239

    View details for Web of Science ID 000265439000005

  • Organic compound alteration during hypervelocity collection of carbonaceous materials in aerogel METEORITICS & PLANETARY SCIENCE Spencer, M. K., Clemett, S. J., Sandford, S. A., McKay, D. S., Zare, R. N. 2009; 44 (1): 15-24

    View details for Web of Science ID 000264476300002

  • Time-dependent depolarization of aligned HD molecules PHYSICAL CHEMISTRY CHEMICAL PHYSICS Bartlett, N. C., Miller, D. J., Zare, R. N., Alexander, A. J., Sofikitis, D., Rakitzis, T. P. 2009; 11 (1): 142-147

    Abstract

    An aligned sample of HD(v = 1, J = 2, M(J) = 0) molecules is prepared under collision-free conditions using the S(0) stimulated Raman pumping transition. Subsequent coupling to the spins of the deuteron I(D) and the proton I(H) causes the initial degree of alignment to oscillate and decrease as monitored over the time range from 0-13 mus via the O2 line of the [2 + 1] REMPI E,F(1)Sigma-X(1)Sigma (0,1) band. The time dependence of the rotational alignment is also calculated using both a hierarchical coupling scheme in which the rotational angular momentum J is regarded first to couple to I(D), and then the resultant F(i) to couple to I(H), to form the total angular momentum F and a non-hierarchical coupling scheme in which the HD energy level structure is not assumed to be diagonal in the |I(H)(JI(D))F(i)FM(F)> basis set. The experimental data is in good agreement with the non-hierarchical calculation but not with the hierarchical calculation, as expected for this system. Additionally, we calculate the time dependence of the H and D nuclear spin polarizations.

    View details for DOI 10.1039/b814133a

    View details for PubMedID 19081917

  • Laser mass spectrometric detection of extraterrestrial aromatic molecules: Mini-review and examination of pulsed heating effects PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Spencer, M. K., Hammond, M. R., Zare, R. N. 2008; 105 (47): 18096-18101

    Abstract

    Laser mass spectrometry is a powerful tool for the sensitive, selective, and spatially resolved analysis of organic compounds in extraterrestrial materials. Using microprobe two-step laser mass spectrometry (muL(2)MS), we have explored the organic composition of many different exogenous materials, including meteorites, interplanetary dust particles, and interstellar ice analogs, gaining significant insight into the nature of extraterrestrial materials. Recently, we applied muL(2)MS to analyze the effect of heating caused by hypervelocity particle capture in aerogel, which was used on the NASA Stardust Mission to capture comet particles. We show that this material exhibits complex organic molecules upon sudden heating. Similar pulsed heating of carbonaceous materials is shown to produce an artifactual fullerene signal. We review the use of muL(2)MS to investigate extraterrestrial materials, and we discuss its recent application to characterize the effect of pulsed heating on samples of interest.

    View details for DOI 10.1073/pnas.0801860105

    View details for Web of Science ID 000261489300014

    View details for PubMedID 18687897

    View details for PubMedCentralID PMC2587552

  • Vibrationally inelastic H + D-2 collisions are forward-scattered PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Goldberg, N. T., Zhang, J., Koszinowski, K., Bouakline, F., Althorpe, S. C., Zare, R. N. 2008; 105 (47): 18194-18199

    Abstract

    We have measured differential cross sections (DCSs) for the vibrationally inelastic scattering process H + o-D(2)(v = 0, j = 0,2) --> H + o-D(2)(v' = 1-4, j' even). Several different collision energies and nearly the entire range of populated product quantum states are studied. The products are dominantly forward-scattered in all cases. This behavior is the opposite of what is predicted by the conventional textbook mechanism, in which collisions at small impact parameters compress the bond and cause the products to recoil in the backward direction. Recent quasiclassical trajectory (QCT) calculations examining only the o-D(2)(v' = 3, j') products suggest that vibrationally inelastic scattering is the result of a frustrated reaction in which the D-D bond is stretched, but not broken, during the collision. These QCT calculations provide a qualitative explanation for the observed forward-scattering, but they do not agree with experiments at the lowest values of j'. The present work shows that quantum mechanical calculations agree closely with experiments and expands upon previous results to show that forward-scattering is universally observed in vibrationally inelastic H + D(2) collisions over a broad range of conditions.

    View details for DOI 10.1073/pnas.0807942105

    View details for Web of Science ID 000261489300030

    View details for PubMedID 19015513

    View details for PubMedCentralID PMC2587579

  • Identifying the source of a strong fullerene envelope arising from laser desorption mass spectrometric analysis of meteoritic insoluble organic matter GEOCHIMICA ET COSMOCHIMICA ACTA Hammond, M. R., Zare, R. N. 2008; 72 (22): 5521-5529

    View details for DOI 10.1016/j.gca.2008.08.008

    View details for Web of Science ID 000260562900012

  • Continuous Time-of-Flight Ion Imaging: Application to Fragmentation ANALYTICAL CHEMISTRY Yoon, O. K., Robbins, M. D., Zuleta, I. A., Barbula, G. K., Zare, R. N. 2008; 80 (21): 8299-8307

    Abstract

    We have designed and constructed a continuous imaging reflectron time-of-flight mass spectrometer (TOFMS) that provides a mass spectrum at every pixel of a two-dimensional image with a 100% duty cycle. The technique is based on pseudorandom ion beam modulation and three-dimensional ( x, y, t) ion imaging. We use a multichannel plate detector with a delay-line anode that provides x, y positions and flight times t of every ion arrival event. The precision of the peak heights in the 100% duty cycle mass spectra is shown to be enhanced even at short (10 ms) acquisition times, which should prove useful for the study of solution kinetics or fast chromatographic separations. As a demonstration of the system's capability, we have imaged the fragmented ions that underwent surface-induced dissociation inside the reflectron and the ions that fragmented spontaneously through postsource decay.

    View details for DOI 10.1021/ac801512n

    View details for Web of Science ID 000260567000055

    View details for PubMedID 18837560

  • On the quantum and quasiclassical angular distributions of photofragments JOURNAL OF CHEMICAL PHYSICS Beswick, J. A., Zare, R. N. 2008; 129 (16)

    Abstract

    Quantum and quasiclassical expressions for the angular distribution of photofragments from an initially polarized precursor molecule are compared under the conditions of a one-photon electric dipole transition to a repulsive state followed by prompt axial recoil into two separating fragments. The treatment is most readily applicable to diatomic molecules, but it is more general than that. It is shown that when the rotational and electronic angular momentum J(i) and its projection along the body-fixed z axis Omega(i) are well defined in the initial state, the quantum and quasiclassical expressions are identical for any initial polarization of the molecule prior to photolysis and for all values of J(i) and Omega(i). For the particular case of an mid R:J(i)Omega(i)M(i) selected state this is in agreement with a previous result [T. Seideman, Chem. Phys. Lett. 253, 279 (1996)]. Moreover, the quasiclassical expression is still a good approximation even when the initial state is a coherent superposition of mid R:J(i),Omega(i),M(i) levels for the same Omega(i). This near identity still pertains even when Omega(i) is not well defined for a parallel transition (DeltaOmega=0) but fails for a perpendicular transition (DeltaOmega=+/-1) if the initial state is in a coherent superposition of Omega(i) states differing by +/-2. These conclusions apply to preparation schemes employing optical excitation, static inhomogeneous and/or homogeneous electric and/or magnetic fields, as well as to molecules physisorbed on solids or clusters. We discuss the importance of these results in the interpretation of photofragment distributions when some other angular momenta are involved, such as electronic angular momentum, with and without nuclear spin, coupled to molecular rotation, asymmetric top rotational angular momentum, or internal vibrational angular momentum in polyatomics.

    View details for DOI 10.1063/1.3000581

    View details for Web of Science ID 000260572300037

    View details for PubMedID 19045274

  • Corroboration of theory for H+D-2 -> D+HD (v '=3, j '=0) reactive scattering dynamics JOURNAL OF PHYSICAL CHEMISTRY A Goldberg, N. T., Zhang, J., Miller, D. J., Zare, R. N. 2008; 112 (39): 9266-9268

    Abstract

    The differential cross section (DCS) for the reaction H + D2 --> D + HD (v' = 3, j' = 0) exhibits particularly rich dynamics; in addition to the expected direct recoil backscattering feature, a surprising time-delayed forward scattering feature appears that has been attributed to glory scattering arising from nearside and farside interference. This fact leads to a complex DCS that depends strongly on the collision energy. Its accurate calculation requires a fully quantum mechanical (QM) treatment. We report improved measurements of this DCS over the collision energy range 1.55 < or = E(coll) < or = 1.82 eV. Previous measurements using the core extraction method, while generally in agreement with theory, lacked sufficient resolution to capture all of the noteworthy behavior of the system; in the present work, we use ion imaging to observe many previously unresolved features of the DCS, particularly in the forward-scattered region. Agreement with QM calculations is found at all collision energies, reconciling an earlier discrepancy between experiment and theory near E(coll) = 1.54 eV.

    View details for DOI 10.1021/jp801187p

    View details for PubMedID 18435532

  • Perforated membrane method for fabricating three-dimensional polydimethylsiloxane microfluidic devices LAB ON A CHIP Luo, Y., Zare, R. N. 2008; 8 (10): 1688-1694

    Abstract

    A procedure is described for making layer-to-layer interconnections in polydimethylsiloxane (PDMS) microfluidic devices. Thin (approximately 50 microm) perforated PDMS membranes are bonded to thicker (0.1 cm or more) PDMS slabs by means of thermally cured PDMS prepolymer to form a three-dimensional (3D) channel structure, which may contain channel or valve arrays that can pass over and under one another. Devices containing as many as two slabs and three perforated membranes are demonstrated. We also present 3D PDMS microfluidic devices for display and for liquid dispensing.

    View details for DOI 10.1039/b807751g

    View details for Web of Science ID 000260466300013

    View details for PubMedID 18813392

  • Preparation of oriented and aligned H-2 and HD by stimulated Raman pumping JOURNAL OF CHEMICAL PHYSICS Bartlett, N. C., Miller, D. J., Zare, R. N., Sofikitis, D., Rakitzis, T. P., Alexander, A. J. 2008; 129 (8)

    Abstract

    Stimulated Raman pumping has been used to prepare oriented and aligned samples of H(2)(nu=1,J=1,2,3) and HD(nu=1,J=2) under collision-free conditions using the (1,0) S(0), S(1), Q(1), Q(2), and O(3) lines. The M-sublevel anisotropies were interrogated by polarized [2+1] resonance-enhanced multiphoton ionization via the (0,1) O(2), O(3), and S(1) lines of the E,F (1)Sigma(g) (+)-X (1)Sigma(g) (+) system. The optical excitation schemes employed in this study generate highly oriented and aligned molecular ensembles. We show that the H(2)(nu=1,J=2,M=0) and H(2)(nu=1,J=2,M=2) samples retain their initial polarization for greater than 100 ns and are therefore suitable candidates for targets or projectiles in future scattering experiments.

    View details for DOI 10.1063/1.2973628

    View details for PubMedID 19044828

  • Folding control and unfolding free energy of yeast iso-1-cytochrome c bound to layered zirconium phosphate materials monitored by surface plasmon resonance JOURNAL OF PHYSICAL CHEMISTRY B Bhambhani, A., Chah, S., Hvastkovs, E. G., Jensen, G. C., Rusling, J. F., Zare, R. N., Kumar, C. V. 2008; 112 (30): 9201-9208

    Abstract

    The free energy change (Delta G degrees ) for the unfolding of immobilized yeast iso-1-cytochrome c (Cyt c) at nanoassemblies was measured by surface plasmon resonance (SPR) spectroscopy. Data show that SPR is sensitive to protein conformational changes, and protein solid interface exerts a major influence on bound protein stability. First, Cyt c was self-assembled on the Au film via the single thiol of Cys-102. Then, crystalline sheets of layered alpha-Zr(O(3)POH)(2).H(2)O (alpha-ZrP) or Zr(O(3)PCH(2)CH(2)COOH)(2).xH(2)O (alpha-ZrCEP) were adsorbed to construct alpha-ZrP/Cyt c/Au or alpha-ZrCEP/Cyt c/Au nanoassemblies. The construction of each layer was monitored by SPR, in real time, and the assemblies were further characterized by atomic force microscopy and electrochemical studies. Thermodynamic stability of the protein nanoassembly was assessed by urea-induced unfolding. Surprisingly, unfolding is reversible in all cases studied here. Stability of Cyt c in alpha-ZrP/Cyt c/Au increased by approximately 4.3 kJ/mol when compared to the unfolding free energy of Cyt c/Au assembly. In contrast, the protein stability decreased by approximately 1.5 kJ/mol for alpha-ZrCEP/Cyt c/Au layer. Thus, OH-decorated surfaces stabilized the protein whereas COOH-decorated surfaces destabilized it. These data quantitate the role of specific functional groups of the inorganic layers in controlling bound protein stability.

    View details for DOI 10.1021/jp7121642

    View details for Web of Science ID 000257926800048

    View details for PubMedID 18598069

    View details for PubMedCentralID PMC3490220

  • Capture of phosphopeptides using alpha-zirconium phosphate nanoplatelets ANALYTICAL CHEMISTRY Xu, S., Whitin, J. C., Yu, T. T., Zhou, H., Sun, D., Sue, H., Zou, H., Cohen, H. J., Zare, R. H. 2008; 80 (14): 5542-5549

    Abstract

    Alpha-zirconium phosphate nanoplatelets (alpha-ZrPN) were studied as a binding agent for phosphopeptides. Nanoplatelets of alpha-zirconium phosphate were incubated overnight with zirconium oxychloride, followed by centrifugation, and washed twice with water followed by an aqueous solution of 80% acetonitrile to form the binding agent. Alpha-ZrPN were able specifically to capture phosphoserine-containing peptides from a tryptic digest of a complex peptide mixture in which its abundance was only 0.05%. Alpha-ZrPN also bound peptides containing phosphothreonine and phosphotyrosine. The limit of detection for phosphopeptides is approximately 2 fmol, based on using matrix-assisted laser desorption/ionization mass spectrometry. Alpha-ZrPN were applied for the analysis of tryptic digests of mouse liver and leukemia cell phosphoproteomes and succeeded in identifying 158 phosphopeptides (209 phosphorylation sites) from 101 phosphoproteins in mouse liver lysate and 78 phosphopeptides (104 phosphorylation sites) from 59 phosphoproteins in leukemia cell extract. For these two tryptic digests, the alpha-ZrPN approach is able to capture more phosphopeptides than that obtained from TiO2 particles or from Fe(3+)-IMAC beads, but each method is able to bind some phosphopeptides that the others do not.

    View details for DOI 10.1021/ac800577z

    View details for Web of Science ID 000257598100036

    View details for PubMedID 18522436

  • Vibrational excitation through tug-of-war inelastic collisions NATURE Greaves, S. J., Wrede, E., Goldberg, N. T., Zhang, J., Miller, D. J., Zare, R. N. 2008; 454 (7200): 88-91

    Abstract

    Vibrationally inelastic scattering is a fundamental collision process that converts some of the kinetic energy of the colliding partners into vibrational excitation(,). The conventional wisdom is that collisions with high impact parameters (where the partners only 'graze' each other) are forward scattered and essentially elastic, whereas collisions with low impact parameters transfer a large amount of energy into vibrations and are mainly back scattered. Here we report experimental observations of exactly the opposite behaviour for the simplest and most studied of all neutral-neutral collisions: we find that the inelastic scattering process H + D(2)(v = 0, j = 0, 2) --> H + D(2)(v' = 3, j' = 0, 2, 4, 6, 8) leads dominantly to forward scattering (v and j respectively refer to the vibrational and rotational quantum numbers of the D(2) molecule). Quasi-classical trajectory calculations show that the vibrational excitation is caused by extension, not compression, of the D-D bond through interaction with the passing H atom. However, the H-D interaction never becomes strong enough for capture of the H atom before it departs with diminished kinetic energy; that is, the inelastic scattering process is essentially a frustrated reaction in which the collision typically excites the outward-going half of the H-D-D symmetric stretch before the H-D(2) complex dissociates. We suggest that this 'tug of war' between H and D(2) is a new mechanism for vibrational excitation that should play a role in all neutral-neutral collisions where strong attraction can develop between the collision partners.

    View details for DOI 10.1038/nature07079

    View details for Web of Science ID 000257308300042

    View details for PubMedID 18596807

  • Two-step laser mass spectrometry of asphaltenes JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Pomerantz, A. E., Hammond, M. R., Morrow, A. L., Mullins, O. C., Zare, R. N. 2008; 130 (23): 7216-?

    Abstract

    Defined by their solubility in toluene and insolubility in n-heptane, asphaltenes are a highly aromatic, polydisperse mixture consisting of the heaviest and most polar fraction of crude oil. Although asphaltenes are critically important to the exploitation of conventional oil and are poised to rise in significance along with the exploitation of heavy oil, even as fundamental a quantity as their molecular weight distribution is unknown to within an order of magnitude. Laser desorption/ionization (LDI) mass spectra vary greatly with experimental parameters so are difficult to interpret: some groups favor high laser pulse energy measurements (yielding heavy molecular weights), arguing that high pulse energy is required to detect the heaviest components of this mixture; other groups favor low pulse energy measurements (yielding light molecular weights), arguing that low pulse energy is required to avoid aggregation in the plasma plume. Here we report asphaltene mass spectra recorded with two-step laser mass spectrometry (L2MS), in which desorption and ionization are decoupled and no plasma is produced. L2MS mass spectra of asphaltenes are insensitive to laser pulse energy and other parameters, demonstrating that the asphaltene molecular weight distribution can be measured without limitation from insufficient laser pulse energy or plasma-phase aggregation. These data resolve the controversy from LDI, showing that the asphaltene molecular weight distribution peaks near 600 Da and previous measurements reporting much heavier species suffered from aggregation effects.

    View details for DOI 10.1021/ja801927v

    View details for Web of Science ID 000256550600025

    View details for PubMedID 18484722

  • Computer-controlled, variable-frequency power supply for driving multipole ion guides REVIEW OF SCIENTIFIC INSTRUMENTS Robbins, M. D., Yoon, O. K., Zuleta, I., Barbula, G. K., Zare, R. N. 2008; 79 (3)

    Abstract

    A high voltage, variable-frequency driver circuit for powering resonant multipole ion guides is presented. Two key features of this design are (1) the use of integrated circuits in the driver stage and (2) the use a stepper motor for tuning a large variable capacitor in the resonant stage. In the present configuration the available frequency range spans a factor of 2. The actual values of the minimum and maximum frequencies depend on the chosen inductor and the capacitance of the ion guide. Feedback allows for stabilized, computer-adjustable rf amplitudes over the range of 5-500 V. The rf power supply was characterized over the range of 350-750 kHz and evaluated by driving a quadrupole ion guide in an electrospray time-of-flight mass spectrometer.

    View details for DOI 10.1063/1.2884148

    View details for Web of Science ID 000254538100047

    View details for PubMedID 18377035

  • Vibrationally Inelastic H+D2 Collisions Are Forward Scattered Proc. Natl. Acad. Sci. USA Goldberg, N. T., Zhang, J., Koszinowski, K., Bouakline, F., Althorpe, S. C., Zare, R. N. 2008: 18194–18199
  • Questions to Chemical Educations from the Chemistry Community Nuts and Bolts of Chemical Education Research Zare, R. N. edited by Bunce, D. M., Cole, R. S. Oxford, UK: Oxford University Press. 2008: 11–18
  • Afterword Chemical Evolution Across Space and Time: From the Big Bang to Prebiotic Chemistry Zare, R. N. edited by Zaikowski, L., Friedrich, J. M. 2008: 389–90
  • Microfluidic device for immunoassays based on surface plasmon resonance imaging LAB ON A CHIP Luo, Y., Yu, F., Zare, R. N. 2008; 8 (5): 694-700

    Abstract

    We have designed and fabricated a polydimethylsiloxane (PDMS) microfluidic device containing an array of gold spots onto which antigens or antibodies of interest can be attached. We use surface plasmon resonance (SPR) imaging to monitor the antibody-antigen recognition and binding events. This combination offers two significant advantages: (1) the microfluidic device dramatically reduces reaction time and sample consumption; and (2) the SPR imaging yields real-time detection of the immunocomplex formation. Thus, an immunoreaction may be detected and quantitatively characterized in about 10 min. The sensitivity of this method is at the subnanomolar level. When gold nanoparticles are selectively coupled to the immunocomplex to cause signal amplification, the sensitivity reaches the ten to one hundred picomolar level but the time required increases to about 60 min.

    View details for DOI 10.1039/b800606g

    View details for Web of Science ID 000255276700009

    View details for PubMedID 18432338

  • Surface plasmon resonance study of vesicle rupture by virus-mimetic attack PHYSICAL CHEMISTRY CHEMICAL PHYSICS Chah, S., Zare, R. N. 2008; 10 (22): 3203-3208

    Abstract

    Frank and coworkers [N. J. Cho, S. J. Cho, K. H. Cheong, J. S. Glenn and C. W. Frank, J. Am. Chem. Soc., 2007, 129, 10050] investigated what happens when lipid vesicles made of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), which serves as a mimic for cell membranes, are exposed to the amphipathic helix peptide, PEP1, which is of the same type found in hepatitis C virus. Using atomic force field microscopy and quartz crystal microbalance measurements they presented evidence that the vesicle is transformed into a lipid bilayer. We use surface plasmon resonance (SPR) microscopy to follow this process in real time. We find an induction period (intermediate state) of approximately 10-min duration between the time of membrane binding and membrane rupture. The SPR data support the interpretation that a lipid bilayer is formed and allow us to put forward a mechanism for the vesicle-rupture event. As a side benefit, we demonstrate how to build two-dimensional lipid patterns on a gold surface using this vesicle-rupture process.

    View details for DOI 10.1039/b802632g

    View details for Web of Science ID 000256114700003

    View details for PubMedID 18500396

  • Sustained release of drugs dispersed in polymer nanoparticles ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Jacobson, G. B., Shinde, R., Contag, C. H., Zare, R. N. 2008; 47 (41): 7880-7882

    View details for DOI 10.1002/anie.200802260

    View details for Web of Science ID 000260062500019

    View details for PubMedID 18773393

    View details for PubMedCentralID PMC2586612

  • Micromachined Bradbury-Nielsen gates ANALYTICAL CHEMISTRY Zuleta, I. A., Barbula, G. K., Robbins, M. D., Yoon, O. K., Zare, R. M. 2007; 79 (23): 9160-9165

    Abstract

    Bradbury-Nielsen gates (BNGs) are a standard way for gating or steering beams of charged particles in ion mobility spectrometry and time-of-flight mass spectrometry. They consist of a pair of interleaved electrodes that when at the same potential allow ions to pass through the electrodes undeflected and, when a voltage is applied, cause the ions to be deflected from their propagation axis. Previous efforts to construct such devices have relied on mechanical assembly by winding wires across an aperture. We describe a micromachining method for making monolithic BNGs using deep reactive ion etching of silicon-on-insulator wafers. This method enables the creation of electrodes with spacings ranging from 25 to 100 microm with a thickness of 20 microm, covering a 5 mm by 5 mm active area. We characterize the performance of these micromachined BNGs by ion imaging in a pseudorandom time-of-flight mass spectrometer.

    View details for DOI 10.1021/ac071581e

    View details for Web of Science ID 000251311900049

    View details for PubMedID 17966990

  • Use of a mixture of n-dodecyl-beta-D-maltoside and sodium dodecyl sulfate in poly(dimethylsiloxane) microchips to suppress adhesion and promote separation of proteins ANALYTICAL CHEMISTRY Huang, B., Kim, S., Wu, H., Zare, R. N. 2007; 79 (23): 9145-9149

    Abstract

    Dynamic modification of poly(dimethylsiloxane) channels using a mixture of n-dodecyl-beta-D-maltoside (DDM) and sodium dodecyl sulfate (SDS) is able to suppress analyte adsorption and control electroosmotic flow (EOF). In this mixed surfactant system, the nonionic surfactant DDM functions as a surface blocking reagent, whereas the anionic surfactant SDS introduces negative charges to the channel walls. Changing the DDM/SDS mixing ratio tunes the surface charge density and the strength of EOF. Using 0.1% (w/v) DDM and 0.03% (w/v) SDS, Alexa Fluor 647 labeled streptavidin can be analyzed according to the charges added by the fluorophores. Protein molecules with different numbers of fluorophores are well resolved. DDM and SDS also form negatively charged mixed micelles, which act as a separation medium. The low critical micellar concentration of DDM/SDS mixed micelles also allows the use of SDS at a nondenaturing concentration, which enables the analysis of proteins in their native state. The immunocomplex between a membrane protein, beta2 adrenergic receptor, and anti-FLAG antibody has been fully separated using 0.1% (w/v) DDM and 0.03% (w/v) SDS. We have also analyzed the composition of light-harvesting protein-chromophore complexes in cyanobacteria.

    View details for DOI 10.1021/ac071544n

    View details for Web of Science ID 000251311900047

    View details for PubMedID 17948969

  • Visible light-induced photopolymerization of an in situ macroporous sol-gel monolith JOURNAL OF SEPARATION SCIENCE Dulay, M. T., Choi, H. N., Zare, R. N. 2007; 30 (17): 2979-2985

    Abstract

    A one-step, in situ, photopolymerization of a mixture of methacryloxypropyltrimethoxysilane in the presence of an acid catalyst, water, and toluene is accomplished in a 75 microm id polyimide-coated capillary using visible light (460 nm) for a 15 min irradiation time. The mixture is a two-component photosystem comprising Irgacure 784 photosensitizer and diphenyliodonium chloride photoinitiator. The visible photopolymerized sol-gel (vis-PSG) column shows RP chromatographic behavior. The analytical potential of these columns is demonstrated with the isocratic separation of small, neutral alkyl phenyl ketones. Operational parameters, such as mobile phase composition, field strength, and column temperature were varied to assess how they affect the separation performance of the monolith.

    View details for DOI 10.1002/jssc.200700328

    View details for Web of Science ID 000251461500024

    View details for PubMedID 17960846

  • Simple template-based method to produce Bradbury-Nielsen gates JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Yoon, O. K., Zuleta, I. A., Robbins, M. D., Barbula, G. K., Zare, R. N. 2007; 18 (11): 1901-1908

    Abstract

    A Bradbury-Nielsen gate (BNG) consists of two interleaved and electrically isolated sets of wires and can transmit or deflect charged particles by applying a varying voltage difference across the two wire sets. We present a simple template-based method to fabricate BNGs with wire spacings as small as 50 microm with minimal use of a microscope. The small wire spacing allows modulation rates at tens of megahertz. Using this method, we have fabricated four BNGs with wire spacings of 500, 200, 100, and 50 microm using 10 microm gold-coated tungsten wires. The performance of the four BNGs is characterized using an imaging detector and compared with theoretical predictions.

    View details for DOI 10.1016/j.jasms.2007.07.030

    View details for Web of Science ID 000250844900001

    View details for PubMedID 17827033

  • Optical control of ground-state atomic orbital alignment: Cl(2P3/2) atoms from HCl(v=2,J=1) photodissociation. journal of chemical physics Sofikitis, D., Rubio-Lago, L., Martin, M. R., Ankeny Brown, D. J., Bartlett, N. C., Alexander, A. J., Zare, R. N., Rakitzis, T. P. 2007; 127 (14): 144307-?

    Abstract

    H(35)Cl(v=0,J=0) molecules in a supersonic expansion were excited to the H(35)Cl(v=2,J=1,M=0) state with linearly polarized laser pulses at about 1.7 microm. These rotationally aligned J=1 molecules were then selectively photodissociated with a linearly polarized laser pulse at 220 nm after a time delay, and the velocity-dependent alignment of the (35)Cl((2)P(32)) photofragments was measured using 2+1 REMPI and time-of-flight mass spectrometry. The (35)Cl((2)P(32)) atoms are aligned by two mechanisms: (1) the time-dependent transfer of rotational polarization of the H(35)Cl(v=2,J=1,M=0) molecule to the (35)Cl((2)P(32)) nuclear spin [which is conserved during the photodissociation and thus contributes to the total (35)Cl((2)P(32)) photofragment atomic polarization] and (2) the alignment of the (35)Cl((2)P(32)) electronic polarization resulting from the photoexcitation and dissociation process. The total alignment of the (35)Cl((2)P(32)) photofragments from these two mechanisms was found to vary as a function of time delay between the excitation and the photolysis laser pulses, in agreement with theoretical predictions. We show that the alignment of the ground-state (35)Cl((2)P(32)) atoms, with respect to the photodissociation recoil direction, can be controlled optically. Potential applications include the study of alignment-dependent collision effects.

    View details for PubMedID 17935395

  • Optical control of ground-state atomic orbital alignment: Cl(P-2(3/2)) atoms from HCl(v=2,J=1) photodissociation JOURNAL OF CHEMICAL PHYSICS Sofikitis, D., Rubio-Lago, L., Martin, M. R., Ankeny, D. J., Bartlett, N. C., Alexander, A. J., Zare, R. N., Rakitzis, T. P. 2007; 127 (14)

    View details for DOI 10.1063/1.2772272

    View details for Web of Science ID 000250140800021

  • Differential cross section for the H+D-2 -> HD(v '=1,j '=2,6,10)+D reaction as a function of collision energy JOURNAL OF CHEMICAL PHYSICS Koszinowski, K., Goldberg, N. T., Zhang, J., Zare, R. N., Bouakline, F., Althorpe, S. C. 2007; 127 (12)

    Abstract

    We have measured differential cross sections (DCSs) for the HD (v(')=1,j(')=2,6,10) products of the H+D(2) exchange reaction at five different collision energies in the range 1.48< or =E(coll)< or =1.94 eV. The contribution from the less energetic H atoms formed upon spin-orbit excitation of Br in the photolysis of the HBr precursor is taken into account for two collision energies, E(coll)=1.84 and 1.94 eV, allowing us to disentangle the two different channels. The measured DCSs agree well with new time-dependent quantum-mechanical calculations. As the product rotational excitation increases, the DCSs shift from backward to sideward scattering, as expected. We also find that the shapes of the DCSs show only a small overall dependence on the collision energy, with a notable exception occurring for HD (v(')=1,j(')=2), which appears bimodal at high collision energies. We suggest that this feature results from both direct recoil and indirect scattering from the conical intersection.

    View details for DOI 10.1063/1.2771157

    View details for Web of Science ID 000249787300027

    View details for PubMedID 17902911

  • Comment on "Organics captured from Comet 81P/Wild 2 by the Stardust spacecraft" SCIENCE Spencer, M. K., Zare, R. N. 2007; 317 (5845)

    Abstract

    Sandford et al. (Reports, 15 December 2006, p. 1720) reported on organic compounds captured from Comet 81P/Wild 2 by the Stardust spacecraft. We emphasize the difficulty in assigning the origin of compounds detected diffusely along particle impact tracks and show that rapid heating of aerogel that has never been exposed to cometary particle capture can generate complex aromatic molecules from low-mass carbon impurities present in the aerogel.

    View details for DOI 10.1126/science.1142407

    View details for PubMedID 17885115

  • Detection of separated analytes in subnanoliter volumes using coaxial thermal lensing ANALYTICAL CHEMISTRY Li, F., Kachanov, A. A., Zare, R. N. 2007; 79 (14): 5264-5271

    Abstract

    A collinear-beam thermal lens detector has been constructed and its properties were characterized. Its application to the high-performance liquid chromatography (HPLC) separation of a mixture of five anthraquinone dyes dissolved in water shows a linear response over 3.5 orders of magnitude and a detection limit that is subnanomolar in the dye concentrations. These results are compared with those obtained previously using cavity ring-down spectroscopy (CRDS) in a Brewster's angle flow cell (Bechtel, K. L.; Zare, R. N.; Kachanov, A. A.; Sanders, S. S.; Paldus, B. A. Anal. Chem. 2005, 77, 1177-1182). The peak-to-peak baseline noise of the thermal lensing detection is 3.5 x 10(-8) absorbance units (AU) with a path length of 200 microm, whereas the peak-to-peak baseline noise of CRDS detection is approximately 2 x 10(-7) AU with a path length of 300 microm. Both of these figures of merit should be compared to the peak-to-peak baseline noise of one of the best commercial UV-vis HPLC detection systems, which is approximately 5 x 10(-6) AU with a path length of 10 mm (1-s integration time). Therefore, the thermal lensing technique has a demonstrated sensitivity of subnanomolar detection that is approximately 140 times better than that of the best commercial UV-vis detector and approximately 5 times better than that of CRDS.

    View details for DOI 10.1021/ac0705925

    View details for Web of Science ID 000247992600021

    View details for PubMedID 17569503

  • Preparation of highly polarized nuclei: Observation and control of time-dependent polarization transfer from (HCl)-Cl-35 molecular rotation to Cl-35 nuclear spin PHYSICAL REVIEW A Sofikitis, D., Rubio-Lago, L., Martin, M. R., Brown, D. J., Bartlett, N. C., Zare, R. N., Rakitzis, T. P. 2007; 76 (1)

    View details for DOI 10.1103/PhysRevA.76.012503

    View details for Web of Science ID 000248486600078

  • Characterization of two types of silanol groups on fused-silica surfaces using evanescent-wave cavity ring-down spectroscopy ANALYTICAL CHEMISTRY Fan, H., Li, F., Zare, R. N., Lin, K. 2007; 79 (10): 3654-3661

    Abstract

    Evanescent-wave cavity ring-down spectroscopy has been applied to a planar fused-silica surface covered with crystal violet (CV+) cations to characterize the silanol groups indirectly. A radiation-polarization dependence of the adsorption isotherm of CV+ at the CH3CN/silica interface is measured and fit to a two-site Langmuir equation to determine the relative populations of two different types of isolated silanol groups. CV+ binding at type I sites yields a free energy of adsorption of -29.9 +/- 0.2 kJ/mol and a saturation surface density of (7.4 +/- 0.5) x 10(12) cm(-2), whereas the values of -17.9 +/- 0.4 kJ/mol and (3.1 +/- 0.4) x 10(13) cm(-2) are obtained for the type II sites. The CV+ cations, each with a planar area of approximately 120 A2, seem to be aligned randomly while lying over the SiO- type I sites, thereby suggesting that this type of site may be surrounded by a large empty surface area (>480 A2). In contrast, the CV+ cations on a type II sites are restricted with an average angle of approximately 40 degrees tilted off the surface normal, suggesting that the CV+ cations on these sites are grouped closely together. The average tilt angle increases with increasing concentration of crystal violet so that CV+ cations may be separated from each other to minimize the repulsion of nearby CV+ and SiOH sites.

    View details for DOI 10.1021/ac062386n

    View details for Web of Science ID 000246414400017

    View details for PubMedID 17429945

  • Structure and conformational changes in the C-terminal domain of the beta(2)-adrenoceptor - Insights from fluorescence resonance energy transfer studies JOURNAL OF BIOLOGICAL CHEMISTRY Granier, S., Kim, S., Shafer, A. M., Ratnala, V. R., Fung, J. J., Zare, R. N., Kobilka, B. 2007; 282 (18): 13895-13905

    Abstract

    The C terminus of the beta(2)-adrenoceptor (AR) interacts with G protein-coupled receptor kinases and arrestins in an agonist-dependent manner, suggesting that conformational changes induced by ligands in the transmembrane domains are transmitted to the C terminus. We used fluorescence resonance energy transfer (FRET) to examine ligand-induced structural changes in the distance between two positions on the beta(2)-AR C terminus and cysteine 265 (Cys-265) at the cytoplasmic end of transmembrane domain 6. The donor fluorophore FlAsH (Fluorescein Arsenical Helix binder) was attached to a CCPGCC motif introduced at position 351-356 in the proximal C terminus or at the distal C terminus. An acceptor fluorophore, Alexa Fluor 568, was attached to Cys-265. FRET analyses revealed that the average distances between Cys-265 and the proximal and distal FlAsH sites were 57 and 62A(,) respectively. These relatively large distances suggest that the C terminus is in an extended, relatively unstructured conformation. Nevertheless, we observed ligand-specific changes in FRET. All ligands induced an increase in FRET between the proximal C-terminal FlAsH site and Cys-265. Ligands that have been shown to induce arrestin-dependent ERK activation, including the catecholamine agonists and the inverse agonist ICI118551, led to a decrease in FRET between the distal FlAsH site and Cys-265, whereas other ligands had no effect or induced a small increase in FRET. Taken together the results provide new insight into the structure of the C terminus of the beta(2)-AR as well as ligand-induced conformational changes that may be relevant to arrestin-dependent regulation and signaling.

    View details for DOI 10.1074/jbc.M611904200

    View details for Web of Science ID 000246060300079

    View details for PubMedID 17347144

  • A monomeric G protein-coupled receptor isolated in a high-density lipoprotein particle efficiently activates its G protein PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Whorton, M. R., Bokoch, M. P., Rasmussen, S. G., Huang, B., Zare, R. N., Kobilka, B., Sunahara, R. K. 2007; 104 (18): 7682-7687

    Abstract

    G protein-coupled receptors (GPCRs) respond to a diverse array of ligands, mediating cellular responses to hormones and neurotransmitters, as well as the senses of smell and taste. The structures of the GPCR rhodopsin and several G proteins have been determined by x-ray crystallography, yet the organization of the signaling complex between GPCRs and G proteins is poorly understood. The observations that some GPCRs are obligate heterodimers, and that many GPCRs form both homo- and heterodimers, has led to speculation that GPCR dimers may be required for efficient activation of G proteins. However, technical limitations have precluded a definitive analysis of G protein coupling to monomeric GPCRs in a biochemically defined and membrane-bound system. Here we demonstrate that a prototypical GPCR, the beta2-adrenergic receptor (beta2AR), can be incorporated into a reconstituted high-density lipoprotein (rHDL) phospholipid bilayer particle together with the stimulatory heterotrimeric G protein, Gs. Single-molecule fluorescence imaging and FRET analysis demonstrate that a single beta2AR is incorporated per rHDL particle. The monomeric beta2AR efficiently activates Gs and displays GTP-sensitive allosteric ligand-binding properties. These data suggest that a monomeric receptor in a lipid bilayer is the minimal functional unit necessary for signaling, and that the cooperativity of agonist binding is due to G protein association with a receptor monomer and not receptor oligomerization.

    View details for DOI 10.1073/pnas.0611448104

    View details for Web of Science ID 000246239400068

    View details for PubMedID 17452637

    View details for PubMedCentralID PMC1863461

  • Surface plasmon resonance imaging using a high numerical aperture microscope objective ANALYTICAL CHEMISTRY Huang, B., Yu, F., Zare, R. N. 2007; 79 (7): 2979-2983

    Abstract

    We designed, constructed, and tested a surface plasmon resonance (SPR) microscope using a high numerical aperture objective from a commercially available inverted optical microscope. Such a configuration, combined with various methods to shorten the surface plasmon propagation length, achieves diffraction-limited spatial resolution in the transverse direction and near-diffraction-limited resolution in the longitudinal direction. A virtue of the objective-type SPR imaging is that we achieve distortion-free angle-resolved SPR imaging, allowing the angle-dependent reflectivity of the sample to be examined on a pixel-by-pixel basis, thus offering high-resolution information about surface properties.

    View details for DOI 10.1021/ac062284x

    View details for Web of Science ID 000245304300046

    View details for PubMedID 17309232

  • Reaction of Cl with CD4 excited to the second C-D stretching overtone JOURNAL OF CHEMICAL PHYSICS Martin, M. R., Brown, D. J., Chiou, A. S., Zare, R. N. 2007; 126 (4)

    Abstract

    The effects of vibrational excitation on the Cl+CD(4) reaction are investigated by preparing three nearly isoenergetic vibrational states: mid R:3000 at 6279.66 cm(-1), |2100> at 6534.20 cm(-1), and |1110> at 6764.24 cm(-1), where |D(1)D(2)D(3)D(4)> identifies the number of vibrational quanta in each C-D oscillator. Vibrational excitation of the perdeuteromethane is via direct infrared pumping. The reaction is initiated by photolysis of molecular chlorine at 355 nm. The nascent methyl radical product distribution is measured by 2+1 resonance-enhanced multiphoton ionization at 330 nm. The resulting CD(3) state distributions reveal a preference to remove all energy available in the most excited C-D oscillator. Although the energetics are nearly identical, the authors observe strong mode specificity in which the CD(3) state distributions markedly differ between the three Cl-atom reactions. Reaction with CD(4) prepared in the |3000> mode leads to CD(3) products populated primarily in the ground state, reaction with CD(4) prepared in the |2100> mode leads primarily to CD(3) with one quantum of stretch excitation, and reaction with CD(4) prepared in the |1110> mode leads primarily to CD(3) with one quantum of C-D stretch excitation in two oscillators. There are some minor deviations from this behavior, most notably that the Cl atom is able to abstract more energy than is available in a single C-D oscillator, as in the case of |2100>, wherein a small population of ground-state CD(3) is observed. These exceptions likely result from the mixings between different second overtone stretch combination bands. They also measure isotropic and anisotropic time-of-flight profiles of CD(3) (nu(1)=1,2) products from the Cl+CD(4) |2100> reaction, providing speed distributions, spatial anisotropies, and differential cross sections that indicate that energy introduced as vibrational energy into the system essentially remains as such throughout the course of the reaction.

    View details for DOI 10.1063/1.2431368

    View details for PubMedID 17286478

  • Doppler-free ion imaging of hydrogen molecules produced in bimolecular reactions CHEMICAL PHYSICS LETTERS Goldberg, N. T., Koszinowski, K., Pomerantz, A. E., Zare, R. N. 2007; 433 (4-6): 439-443

    View details for DOI 10.1016/j.cplett.2006.11.073

    View details for Web of Science ID 000243900700035

  • Counting low-copy number proteins in a single cell SCIENCE Huang, B., Wu, H., Bhaya, D., Grossman, A., Granier, S., Kobilka, B. K., Zare, R. N. 2007; 315 (5808): 81-84

    Abstract

    We have designed a microfluidic device in which we can manipulate, lyse, label, separate, and quantify the protein contents of a single cell using single-molecule fluorescence counting. Generic labeling of proteins is achieved through fluorescent-antibody binding. The use of cylindrical optics enables high-efficiency (approximately 60%) counting of molecules in micrometer-sized channels. We used this microfluidic device to quantify beta2 adrenergic receptors expressed in insect cells (SF9). We also analyzed phycobiliprotein contents in individual cyanobacterial cells (Synechococcus sp. PCC 7942) and observed marked differences in the levels of specific complexes in cell populations that were grown under nitrogen-depleted conditions.

    View details for DOI 10.1126/science.1133992

    View details for Web of Science ID 000243259100039

    View details for PubMedID 17204646

  • Microfluidic separation and capture of analytes for single-molecule spectroscopy LAB ON A CHIP Kim, S., Huang, B., Zare, R. N. 2007; 7 (12): 1663-1665

    Abstract

    A complex mixture of fluorescently labeled biological molecules is separated electrophoretically on a chip and the constituent molecules are confined in a sub-nanolitre microchamber, which allows analysis by various single-molecule techniques.

    View details for DOI 10.1039/b713103h

    View details for Web of Science ID 000251121000013

    View details for PubMedID 18030384

  • Collaborative Research: The Good, the Bad, and the Beautiful 230th National Meeting of the American-Chemical-Society Heineman, W. R., Zare, R. N. AMER CHEMICAL SOC. 2007: 259–270

    View details for Web of Science ID 000270493500019

  • Organics captured from comet 81P/Wild 2 by the Stardust spacecraft SCIENCE Sandford, S. A., Aleon, J., Alexander, C. M., Araki, T., Bajt, S., Baratta, G. A., Borg, J., Bradley, J. P., Brownlee, D. E., Brucato, J. R., Burchell, M. J., Busemann, H., Butterworth, A., Clemett, S. J., Cody, G., Colangeli, L., Cooper, G., D'Hendecourt, L., Djouadi, Z., Dworkin, J. P., Ferrini, G., Fleckenstein, H., Flynn, G. J., Franchi, I. A., Fries, M., Gilles, M. K., Glavin, D. P., Gounelle, M., Grossemy, F., Jacobsen, C., Keller, L. P., Kilcoyne, A. L., Leitner, J., Matrajt, G., Meibom, A., Mennella, V., Mostefaoui, S., Nittler, L. R., Palumbo, M. E., Papanastassiou, D. A., Robert, F., Rotundi, A., Snead, C. J., Spencer, M. K., Stadermann, F. J., Steele, A., Stephan, T., Tsou, P., Tyliszczak, T., Westphal, A. J., Wirick, S., Wopenka, B., Yabuta, H., Zare, R. N., Zolensky, M. E. 2006; 314 (5806): 1720-1724

    Abstract

    Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

    View details for DOI 10.1126/science.1135841

    View details for Web of Science ID 000242833600043

    View details for PubMedID 17170291

  • Research article - Comet 81P/Wild 2 under a microscope SCIENCE Brownlee, D., Tsou, P., Aleon, J., Alexander, C. M., Araki, T., Bajt, S., Baratta, G. A., Bastien, R., Bland, P., Bleuet, P., Borg, J., Bradley, J. P., Brearley, A., Brenker, F., Brennan, S., Bridges, J. C., Browning, N. D., Brucato, J. R., Bullock, E., Burchell, M. J., Busemann, H., Butterworth, A., Chaussidon, M., Cheuvront, A., Chi, M., Cintala, M. J., Clark, B. C., Clemett, S. J., Cody, G., Colangeli, L., Cooper, G., Cordier, P., Daghlian, C., Dai, Z., D'Hendecourt, L., Djouadi, Z., Dominguez, G., Duxbury, T., Dworkin, J. P., Ebel, D. S., Economou, T. E., Fakra, S., Fairey, S. A., Fallon, S., Ferrini, G., Ferroir, T., Fleckenstein, H., Floss, C., Flynn, G., Franchi, I. A., Fries, M., Gainsforth, Z., Gallien, J., Genge, M., Gilles, M. K., Gillet, P., Gilmour, J., Glavin, D. P., Gounelle, M., Grady, M. M., Graham, G. A., Grant, P. G., Green, S. F., Grossemy, F., Grossman, L., Grossman, J. N., Guan, Y., Hagiya, K., Harvey, R., Heck, P., Herzog, G. F., Hoppe, P., Hoerz, F., Huth, J., Hutcheon, I. D., Ignatyev, K., Ishii, H., Ito, M., Jacob, D., Jacobsen, C., Jacobsen, S., Jones, S., Joswiak, D., Jurewicz, A., Kearsley, A. T., Keller, L. P., Khodja, H., Kilcoyne, A. L., Kissel, J., Krot, A., Langenhorst, F., Lanzirotti, A., Le, L., Leshin, L. A., Leitner, J., Lemelle, L., Leroux, H., Liu, M., Luening, K., Lyon, I., MacPherson, G., Marcus, M. A., Marhas, K., Marty, B., Matrajt, G., McKeegan, K., Meibom, A., Mennella, V., Messenger, K., Messenger, S., Mikouchi, T., Mostefaoui, S., Nakamura, T., Nakano, T., Newville, M., Nittler, L. R., Ohnishi, I., Ohsumi, K., Okudaira, K., Papanastassiou, D. A., Palma, R., Palumbo, M. E., Pepin, R. O., Perkins, D., Perronnet, M., Pianetta, P., Rao, W., Rietmeijer, F. J., Robert, F., Rost, D., Rotundi, A., Ryan, R., Sandford, S. A., Schwandt, C. S., See, T. H., Schlutter, D., Sheffield-Parker, J., Simionovici, A., Simon, S., Sitnitsky, I., Snead, C. J., Spencer, M. K., Stadermann, F. J., Steele, A., Stephan, T., Stroud, R., Susini, J., Sutton, S. R., Suzuki, Y., Taheri, M., Taylor, S., Teslich, N., Tomeoka, K., Tomioka, N., Toppani, A., Trigo-Rodriguez, J. M., Troadec, D., Tsuchiyama, A., Tuzzolino, A. J., Tyliszczak, T., Uesugi, K., Velbel, M., Vellenga, J., Vicenzi, E., Vincze, L., Warren, J., Weber, I., Weisberg, M., Westphal, A. J., Wirick, S., Wooden, D., Wopenka, B., Wozniakiewicz, P., Wright, I., Yabuta, H., Yano, H., Young, E. D., Zare, R. N., Zega, T., Ziegler, K., Zimmerman, L., Zinner, E., Zolensky, M. 2006; 314 (5806): 1711-1716

    Abstract

    The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

    View details for DOI 10.1126/science.1135840

    View details for Web of Science ID 000242833600041

  • Comet 81P/Wild 2 under a microscope. Science Brownlee, D., Tsou, P., Aléon, J., Alexander, C. M., Araki, T., Bajt, S., Baratta, G. A., Bastien, R., Bland, P., Bleuet, P., Borg, J., Bradley, J. P., Brearley, A., Brenker, F., Brennan, S., Bridges, J. C., Browning, N. D., Brucato, J. R., Bullock, E., Burchell, M. J., Busemann, H., Butterworth, A., Chaussidon, M., Cheuvront, A., Chi, M., Cintala, M. J., Clark, B. C., Clemett, S. J., Cody, G., Colangeli, L., Cooper, G., Cordier, P., Daghlian, C., Dai, Z., D'Hendecourt, L., Djouadi, Z., Dominguez, G., Duxbury, T., Dworkin, J. P., Ebel, D. S., Economou, T. E., Fakra, S., Fairey, S. A., Fallon, S., Ferrini, G., Ferroir, T., Fleckenstein, H., Floss, C., Flynn, G., Franchi, I. A., Fries, M., Gainsforth, Z., Gallien, J., Genge, M., Gilles, M. K., Gillet, P., Gilmour, J., Glavin, D. P., Gounelle, M., Grady, M. M., Graham, G. A., Grant, P. G., Green, S. F., Grossemy, F., Grossman, L., Grossman, J. N., Guan, Y., Hagiya, K., Harvey, R., Heck, P., Herzog, G. F., Hoppe, P., Hörz, F., Huth, J., Hutcheon, I. D., Ignatyev, K., Ishii, H., Ito, M., Jacob, D., Jacobsen, C., Jacobsen, S., Jones, S., Joswiak, D., Jurewicz, A., Kearsley, A. T., Keller, L. P., Khodja, H., Kilcoyne, A. L., Kissel, J., Krot, A., Langenhorst, F., Lanzirotti, A., Le, L., Leshin, L. A., Leitner, J., Lemelle, L., Leroux, H., Liu, M., Luening, K., Lyon, I., MacPherson, G., Marcus, M. A., Marhas, K., Marty, B., Matrajt, G., McKeegan, K., Meibom, A., Mennella, V., Messenger, K., Messenger, S., Mikouchi, T., Mostefaoui, S., Nakamura, T., Nakano, T., Newville, M., Nittler, L. R., Ohnishi, I., Ohsumi, K., Okudaira, K., Papanastassiou, D. A., Palma, R., Palumbo, M. E., Pepin, R. O., Perkins, D., Perronnet, M., Pianetta, P., Rao, W., Rietmeijer, F. J., Robert, F., Rost, D., Rotundi, A., Ryan, R., Sandford, S. A., Schwandt, C. S., See, T. H., Schlutter, D., Sheffield-Parker, J., Simionovici, A., Simon, S., Sitnitsky, I., Snead, C. J., Spencer, M. K., Stadermann, F. J., Steele, A., Stephan, T., Stroud, R., Susini, J., Sutton, S. R., Suzuki, Y., Taheri, M., Taylor, S., Teslich, N., Tomeoka, K., Tomioka, N., Toppani, A., Trigo-Rodríguez, J. M., Troadec, D., Tsuchiyama, A., Tuzzolino, A. J., Tyliszczak, T., Uesugi, K., Velbel, M., Vellenga, J., Vicenzi, E., Vincze, L., Warren, J., Weber, I., Weisberg, M., Westphal, A. J., Wirick, S., Wooden, D., Wopenka, B., Wozniakiewicz, P., Wright, I., Yabuta, H., Yano, H., Young, E. D., Zare, R. N., Zega, T., Ziegler, K., Zimmerman, L., Zinner, E., Zolensky, M. 2006; 314 (5806): 1711-1716

    Abstract

    The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

    View details for PubMedID 17170289

  • Construction and calibration of an instrument for three-dimensional ion imaging JOURNAL OF CHEMICAL PHYSICS Koszinowski, K., Goldberg, N. T., Pomerantz, A. E., Zare, R. N. 2006; 125 (13)

    Abstract

    We describe a new instrument based on a delay-line detector for imaging the complete three-dimensional velocity distribution of photoionized products from photoinitiated reactions. Doppler-free [2+1] resonantly enhanced multiphoton ionization (REMPI) of H and D atoms formed upon photolysis of HBr and DBr in the range 203 nm < or = lambda photolysis < or = 243 nm yields radial speeds measured to be accurate within 1% of those calculated. The relative speed resolution is about 5% and limited by photoionization recoil broadening. A relative speed resolution of 3.4% is obtained for [3+1] REMPI, which minimizes the ionization recoil. We also determine the branching ratio between ground-state and spin-orbit-excited product channels and their associated anisotropies. We find that DBr photolysis dynamics differs slightly from its HBr counterpart.

    View details for DOI 10.1063/1.2217742

    View details for Web of Science ID 000241056600069

    View details for PubMedID 17029486

  • On-line biological sample cleanup for electrospray mass spectrometry using sol-gel columns JOURNAL OF CHROMATOGRAPHY B-ANALYTICAL TECHNOLOGIES IN THE BIOMEDICAL AND LIFE SCIENCES Johannesson, N., Pearce, E., Dulay, M., Zare, R. N., Bergquist, J., Markides, K. E. 2006; 842 (1): 70-74

    Abstract

    Using a slight overpressure, a urine sample is loaded onto a monolithic photopolymerized sol-gel column that has been derivatized with hydrophobic carbon chains and then the complex urine matrix is washed with aqueous solution. A buffer containing organic solvent is used to elute the adsorbed peptides by an applied voltage and the sample is then introduced into a mass spectrometer by sheath flow electrospray. The importance of desalting this type of sample is demonstrated by an experiment that shows that the signal intensity of a test solution with neurotensin, sprayed directly into the mass spectrometer, decreased from 4.5x10(4) cps to no detectible signal when just 10% urine is added to the sample solution. We suggest that this procedure may find general application for desalting biological samples prior to mass spectrometric analysis.

    View details for DOI 10.1016/j.jchromb.2006.05.012

    View details for Web of Science ID 000240712700011

    View details for PubMedID 16814621

  • Controlling electroosmotic flow in poly(dimethylsiloxane) separation channels by means of prepolymer additives ANALYTICAL CHEMISTRY Luo, Y., Huang, B., Wu, H., Zare, R. N. 2006; 78 (13): 4588-4592

    Abstract

    The electroosmotic flow (EOF) in a poly(dimethylsiloxane) (PDMS) separation channel can be altered and controlled by adding a carboxylic acid to the prepolymer prior to curing. When the prepolymer is doped with 0.5 wt % undecylenic acid (UDA), the electroosmotic mobility in a modified PDMS channel rises to (7.6 +/- 0.2) x 10(-4) cm(2) V(-1) s(-1) (in HEPES buffer at pH 8.5), which is nearly twice that in the native PDMS channel. Because this modification does not significantly change the hydrophobicity of the PDMS surface, it is possible to combine the modified PDMS with a dynamic coating of n-dodecyl beta-d-maltoside (DDM), which prevents protein sticking (see Huang, B.; Wu, H. K.; Kim, S.; Zare, R. N. Lab Chip 2005, 5, 1005-1007). The modified PDMS channel with a dynamic coating of DDM generates an electroosmotic mobility of (5.01 +/- 0.09) x 10(-4) cm(2) V(-1) s(-1), which shows excellent reproducibility both in successive runs and during storage in water. Combining this surface modification and the dynamic coating of DDM is an effective means for both providing stable EOF in the PDMS channels and preventing protein adsorption on the channel walls. To demonstrate these effects, we show that the electrophoretic separation of immunocomplexes in free solution can be readily accomplished in a microfluidic chip made of UDA-doped (0.5 wt %) PDMS with a dynamic coating of DDM.

    View details for DOI 10.1021/ac052274g

    View details for Web of Science ID 000238665200047

    View details for PubMedID 16808469

  • Perspective - Sex, lies, and Title IX CHEMICAL & ENGINEERING NEWS Zare, R. N. 2006; 84 (20): 46-?

    View details for Web of Science ID 000237585400048

  • UV photolysis of quinoline in interstellar ice analogs METEORITICS & PLANETARY SCIENCE Elsila, J. E., Hammond, M. R., Bernstein, M. P., Sandford, S. A., Zare, R. N. 2006; 41 (5): 785-796

    View details for Web of Science ID 000237674000011

  • Generation of complex, static solution gradients in microfluidic channels JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Wu, H. K., Huang, B., Zare, R. N. 2006; 128 (13): 4194-4195

    Abstract

    A microfluidic device is used to generate a complex gradient of diffusible molecules in a static solution. The gradient is precise and steady both in space and in time. This device, made from poly(dimethylsiloxane), consists of three layers. The molecules in reservoirs on the top layer diffuse through the flat middle layer of hydrogel and reach an equilibrium distribution. Microfluidic channels on the bottom layer that are in close contact with the hydrogel contain free solution that has concentration gradients based on the gradient in the gel. The gradient profile in the channel can be designed to have an arbitrary form (within the range of the existing gradient in the hydrogel) by controlling the local direction of the channel at each point.

    View details for DOI 10.1021/ja058530o

    View details for Web of Science ID 000236518300015

    View details for PubMedID 16568971

  • Chemistry - Resonances in reaction dynamics SCIENCE Zare, R. N. 2006; 311 (5766): 1383-1385

    View details for DOI 10.1126/science.1124421

    View details for Web of Science ID 000236029400024

    View details for PubMedID 16527958

  • H+CD4 abstraction reaction dynamics: Product energy partitioning JOURNAL OF PHYSICAL CHEMISTRY A Hu, W. F., Lendvay, G., Troya, D., Schatz, G. C., Camden, J. P., Bechtel, H. A., Brown, D. J., Martin, M. R., Zare, R. N. 2006; 110 (9): 3017-3027

    Abstract

    This paper presents experimental and theoretical studies of the product energy partitioning associated with the H + CD4 (nu = 0) --> HD + CD3 reaction for the collision energy range 0.5-3.0 eV. The theoretical results are based on quasiclassical trajectories from (1) first principles direct dynamics calculations (B3LYP/6-31G), (2) an empirical surface developed by Espinosa-García [J. Chem. Phys. 2002, 116, 10664] (EG), and (3) two semiempirical surfaces (MSINDO and reparametrized MSINDO). We find that most of the energy appears in product translation at energies just above the reactive threshold; however, HD vibration and rotation become quite important at energies above 1 eV, each accounting for over 20% of the available energy above 1.5 eV, according to the B3LYP calculations. The barrier on the B3LYP surface, though being later than that on EG, predicts significantly higher HD vibrational excitation than EG. This deviation is contradictory to what would be expected on the basis of the Polanyi rules and derives from modest differences in the potential energy surfaces. The CD3 internal energy is generally quite low, and we present detailed rotational state distributions which show that the CD3 rotational distribution is largely independent of collision energy in the 0.75-1.95 eV range. The most populated rotational levels are N = 5 and 6 on B3LYP, with most of that excitation being associated with motion about the C2 axes, rather than C3 axis, of the CD3 product, in good agreement with the experimental results. Through our extensive studies in this and previous work concerning the scattering dynamics, we conclude that B3LYP/6-31G provides the best available description of the overall dynamics for the title reaction at relatively high collision energies.

    View details for DOI 10.1021/jp055017o

    View details for Web of Science ID 000235944000021

    View details for PubMedID 16509623

  • Phospholipid biotinylation of polydimethylsiloxane (PDMS) for protein immobilization LAB ON A CHIP Huang, B., Wu, H. K., Kim, S., Kobilka, B. K., Zare, R. N. 2006; 6 (3): 369-373

    Abstract

    Polydimethylsiloxane (PDMS) surfaces can be functionalized with biotin groups by adding biotinylated phospholipids to the PDMS prepolymer before curing. The addition of beta-D-dodecyl-N-maltoside (DDM) in the solution blocks non-specific protein binding on these functionalized PDMS surfaces. We characterize the surface by measuring fluorescently labeled streptavidin binding. Single molecule tracking shows that the phospholipids are not covalently linked to PDMS polymer chains, but the surface functionalization is not removed by washing. We demonstrate the immobilization of biotinylated antibodies and lectins through biotin-avidin interactions.

    View details for DOI 10.1039/b515840k

    View details for Web of Science ID 000235993800005

    View details for PubMedID 16511619

  • Tribute to Professor S. Terabe JOURNAL OF CHROMATOGRAPHY A Zare, R. N. 2006; 1106 (1-2): 4-4

    View details for DOI 10.1016/j.chroma.2005.10.079

    View details for Web of Science ID 000235256800003

  • Comparing reactions of H and Cl with C-H stretch-excited CHD3 JOURNAL OF CHEMICAL PHYSICS Camden, J. P., Bechtel, H. A., Brown, D. J., Zare, R. N. 2006; 124 (3)

    Abstract

    We report the methyl radical product state distributions for the reactions of H and Cl with CHD3(nu1 = 1,2) at collision energies of 1.53 and 0.18 eV, respectively. Both reactions demonstrate mode selectivity. The resulting state distributions from the H+CHD3(nu1 = 1,2) reactions are well described by a spectator model. The reactions Cl + CHD3(nu1 = 1,2) exhibit similar behavior, but in some aspects the spectator model breaks down. We attribute this breakdown to enhanced intramolecular vibrational redistribution in the Cl + CHD3(nu1 = 1,2) reactions compared to the H + CHD3(nu1 = 1,2) reactions, caused by the interaction of the slower Cl atom with the vibrationally excited CHD3, which is promoted either by its longer collision duration, its stronger coupling, or both.

    View details for DOI 10.1063/1.2155434

    View details for Web of Science ID 000234757400028

    View details for PubMedID 16438587

  • H+CD4 abstraction reaction dynamics: Excitation function and angular distributions JOURNAL OF PHYSICAL CHEMISTRY A Camden, J. P., Hu, W. F., Bechtel, H. A., Brown, D. J., Martin, M. R., Zare, R. N., Lendvay, G., Troya, D., Schatz, G. C. 2006; 110 (2): 677-686

    Abstract

    We compare experimental photoloc measurements and quasi-classical trajectory calculations of the integral cross sections, lab-frame speed distributions, and angular distributions associated with the CD3 products of the H + CD4(nu = 0) --> CD3 + HD reaction at collision energies ranging from 0.5 to 3.0 eV. Of the potential energy surfaces (PES) we explored, the direct dynamics calculations using the B3LYP/6-31G** density functional theory PES provide the best agreement with the experimental measurements. This agreement is likely due to the better overall description that B3LYP provides for geometries well removed from the minimum energy path, even though its barrier height is low by approximately 0.2 eV. In contrast to previous theoretical calculations, the angular distributions on this surface show behavior associated with a stripping mechanism, even at collision energies only approximately 0.1 eV above the reaction barrier. Other potential energy surfaces, which include an analytical potential energy surface from Espinosa-García and a direct dynamics calculation based on the MSINDO semiempirical Hamiltonian, are less accurate and predict more rebound dynamics at these energies than is observed. Reparametrization of the MSINDO surface, though yielding better agreement with the experiment, is not sufficient to capture the observed dynamics. The differences between these surfaces are interpreted using an analysis of the opacity functions, where we find that the wider cone of acceptance on the B3LYP surface plays a crucial role in determining the integral cross sections and angular distributions.

    View details for DOI 10.1021/jp053827u

    View details for Web of Science ID 000234699000036

    View details for PubMedID 16405340

  • Cl + CH4 Reaction Dynamics Vector Correlation and Alignment in Chemistry Camden, J. P., Zare, R. N. edited by Balint-Kurti, G. G., de Miranda, M. P. Daresbury Laboratory, Daresbury, UK. 2006
  • Cytochrome c conformations resolved by the photon counting histogram: Watching the alkaline transition with single-molecule sensitivity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Perroud, T. D., Bokoch, M. P., Zare, R. N. 2005; 102 (49): 17570-17575

    Abstract

    We apply the photon counting histogram (PCH) model, a fluorescence technique with single-molecule sensitivity, to study pH-induced conformational changes of cytochrome c. PCH is able to distinguish different protein conformations based on the brightness of a fluorophore sensitive to its local environment. We label cytochrome c through its single free cysteine with tetramethylrhodamine-5-maleimide (TMR), a fluorophore with specific brightnesses that we associate with specific protein conformations. Ensemble measurements demonstrate two different fluorescence responses with increasing pH: (i) a decrease in fluorescence intensity caused by the alkaline transition of cytochrome c (pH 7.0-9.5), and (ii) an increase in intensity when the protein unfolds (pH 9.5-10.8). The magnitudes of these two responses depend strongly on the molar ratio of TMR used to label cytochrome c. Using PCH we determine that this effect arises from the proportion of a nonfunctional conformation in the sample, which can be differentiated from the functional conformation. We further determine the causes of each ensemble fluorescence response: (i) during the alkaline transition, the fluorophore enters a dark state and discrete conformations are observed, and (ii) as cytochrome c unfolds, the fluorophore incrementally brightens, but discrete conformations are no longer resolved. Moreover, we also show that functional TMR-cytochrome c undergoes a response of identical magnitude regardless of the proportion of nonfunctional protein in the sample. As expected for a technique with single-molecule sensitivity, we demonstrate that PCH can directly observe the most relevant conformation, unlike ensemble fluorometry.

    View details for Web of Science ID 000233849000008

    View details for PubMedID 16314563

  • Reaction products with internal energy beyond the kinematic limit result from trajectories far from the minimum energy path: An example from H+HBr -> H-2+Br JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Pomerantz, A. E., Camden, J. P., Chiou, A. S., Ausfelder, F., Chawla, N., Hase, W. L., Zare, R. N. 2005; 127 (47): 16368-16369

    Abstract

    The importance of reactive trajectories straying far from the minimum energy path is demonstrated for the bimolecular reaction H + HBr --> H2(v', j') + Br at 53 kcal/mol collision energy. Product quantum state distributions are measured and calculated using the quasi-classical trajectory technique, and the calculations indicate that highly internally excited H2 products result from indirect reactive trajectories with bent transition states. A general argument is made suggesting that reaction products with internal energy exceeding a kinematic constraint can, in general, be attributed to reactive collisions straying far from the minimum energy path.

    View details for DOI 10.1021/ja055440a

    View details for PubMedID 16305203

  • Duty cycle and modulation efficiency of two-channel Hadamard transform time-of-flight mass spectrometry JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Yoon, O. K., Zuleta, I. A., Kimmel, J. R., Robbins, M. D., Zare, R. N. 2005; 16 (11): 1888-1901

    Abstract

    Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) is based on the pseudorandom gating of ion packets into a time-of-flight mass-to-charge analyzer. In its typical implementation, the technique is able to monitor continuous ion sources with a 50% duty cycle, independent of all other figures of merit. Recently, we have demonstrated that the duty cycle can be extended to 100% using patterned, two-channel detection. Two-channel HT-TOFMS involves the simultaneous optimization of paired one-channel experiments and imposes more stringent conditions to achieve high-quality spectra. An ion modulation device, known as Bradbury-Nielson Gate (BNG), is central to HT-TOFMS. It is an ideal deflection plate, capable of transmitting or deflecting an ion beam according to a known binary sequence without changing the times-of-flight of the ions. Analytical equations are derived that accurately describe the ion modulation process of the BNG as confirmed by good agreement with SimIon simulations and ion beam imaging experiments. From these expressions, the duty cycle and ion modulation efficiency were calculated for various BNG parameters, ion beam characteristics, and detector dimensions, which permit the optimum conditions to be chosen for the two-channel experiment. We conclude that the outer detector should be three times the maximum deflection angle to detect all deflected ions (100% duty cycle) and that the difference between the modulated ion counts in the sequence elements 0 and 1 should be maximized to achieve high modulation efficiency. This condition is best achieved by tight focusing of the ion beam in the center of the inner detector. When both channels are optimized, the two-channel advantage can be exploited to achieve a further improvement over a single-channel experiment.

    View details for DOI 10.1016/j.jasms.2005.07.025

    View details for Web of Science ID 000233095600020

    View details for PubMedID 16198595

  • Undulatory delamination of thin polymer films on gold surfaces JOURNAL OF PHYSICAL CHEMISTRY B Chah, S., Noolandi, J., Zare, R. N. 2005; 109 (41): 19416-19421

    Abstract

    Using two-dimensional surface plasmon resonance measurements, we have observed the formation of traveling waves in the delamination of thin films of polydimethylsilane (PDMS) exposed to methanol. Films were spin-coated on a gold surface and the methanol was added to the top surface. The stress-induced instability caused by the swelling of the PDMS thin film when its edge is pinned to the gold surface leads to wrinkle formation and propagation at the interface. The periodic pattern is thought to be the result of an Asaro-Tiller-Grinfeld (ATG) instability.

    View details for DOI 10.1021/jp0535644

    View details for Web of Science ID 000232612100056

    View details for PubMedID 16853508

  • Effects of C-H stretch excitation on the H+CH4 reaction JOURNAL OF CHEMICAL PHYSICS Camden, J. P., Bechtel, H. A., Brown, D. J., Zare, R. N. 2005; 123 (13)

    Abstract

    We have investigated the effects of C-H stretching excitation on the H+CH4-->CH3+H2 reaction dynamics using the photo-LOC technique. The CH3 product vibrational state and angular distribution are measured for the reaction of fast H atoms with methane excited in either the antisymmetric stretching fundamental (nu3=1) or first overtone (nu3=2) with a center-of-mass collision energy of Ecoll ranging from 1.52 to 2.20 eV. We find that vibrational excitation of the nu3=1 mode enhances the overall reaction cross section by a factor of 3.0+/-1.5 for Ecoll=1.52 eV, and this enhancement factor is approximately constant over the 1.52-2.20-eV collision energy range. A local-mode description of the CH4 stretching vibration, in which the C-H oscillators are uncoupled, is used to describe the observed state distributions. In this model, the interaction of the incident H atom with either a stretched or an unstretched C-H oscillator determines the vibrational state of the CH3 product. We also compare these results to the similar quantities obtained previously for the Cl+CH4-->CH3+HCl reaction at Ecoll=0.16 eV [Z. H. Kim, H. A. Bechtel, and R. N. Zare, J. Chem. Phys. 117, 3232 (2002); H. A. Bechtel, J. P. Camden, D. J. A. Brown, and R. N. Zare, ibid. 120, 5096 (2004)] in an attempt to elucidate the differences in reactivity for the same initially prepared vibration.

    View details for DOI 10.1063/1.2034507

    View details for Web of Science ID 000232442500016

    View details for PubMedID 16223282

  • Phenanthrene and pyrene sorption and intraparticle diffusion in polyoxymethylene, coke, and activated carbon ENVIRONMENTAL SCIENCE & TECHNOLOGY Ahn, S., Werner, D., Karapanagioti, H. K., McGlothlin, D. R., Zare, R. N., Luthy, R. G. 2005; 39 (17): 6516-6526

    Abstract

    We report sorption isotherms and uptake kinetics for phenanthrene and pyrene with three organic model sorbents: polyoxymethylene (POM), coke, and activated carbon. We combine batch equilibration and kinetic experiments with the direct observation of the long-term diffusion of phenanthrene and pyrene as measured within cross-sectioned particles using microprobe laser-desorption laser-ionization mass spectroscopy (muL2MS). For POM pellets, the intraparticle concentration profiles predicted from kinetic batch experiments and a polymer diffusion model with spherical geometry are in agreement with the independent muL2MS measurements. For coke particles, the apparent diffusivities decreased with smaller particle size. These trends in diffusivities were described by a sorption-retarded pore diffusion model with a particle-size-dependent solid-water partitioning coefficient obtained from apparent equilibrium observed in the kinetic batch studies. For activated carbon, the muL2MS measurements showed faster radial diffusion of phenanthrene and pyrene into the particle interior than predicted from diffusion models based on a single sorption domain and diffusivity. A branched pore kinetic model, comprising polycyclic aromatic hydrocarbon (PAH) macropore diffusion with kinetic exchange of PAH between macroporous and microporous domains, fits the experimental observations better. Because of parallel macro- and microdiffusion processes, nonlinear sorption isotherms, and a concentration-dependent diffusivity, it is not possible to make independent parameter estimations for intraparticle diffusion in activated carbon using our present procedures.

    View details for DOI 10.1021/es050113o

    View details for Web of Science ID 000231723800035

    View details for PubMedID 16190207

  • A reinterpretation of the mechanism of the simplest reaction at an sp3-hybridized carbon atom: H + CD4 --> CD3 + HD. Journal of the American Chemical Society Camden, J. P., Bechtel, H. A., Ankeny Brown, D. J., Martin, M. R., Zare, R. N., Hu, W., Lendvay, G., Troya, D., Schatz, G. C. 2005; 127 (34): 11898-11899

    Abstract

    A comparison between theory and experiment for the benchmark H + CD4 --> HD + CD3 abstraction reaction yields a reinterpretation of the reaction mechanism and highlights the unexpected contribution of a stripping mechanism. Whereas the best analytic surface fails to reproduce experiment, a first-principles direct-dynamics (on the fly) treatment is in good agreement, showing that the H + CD4 reaction exhibits extreme sensitivity to modest differences in the potential energy surface. We find that bent H-D-C transition state geometries play an important role in the dynamics. A simple model that relates the scattering angle impact parameter and cone of acceptance accounts well for the overall reaction dynamics.

    View details for PubMedID 16117502

  • A reinterpretation of the mechanism of the simplest reaction at an spa-hybridized carbon atom: H+CD4 -> CD3+HD JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Camden, J. P., Bechtel, H. A., Brown, D. J., Martin, M. R., Zare, R. N., Hu, W. F., Lendvay, G., Troya, D., Schatz, G. C. 2005; 127 (34): 11898-11899

    View details for DOI 10.1021/ja052684m

    View details for Web of Science ID 000231605900010

  • Collision-energy dependence of HD(nu(')=1,j ') product rotational distributions for the H+D-2 reaction JOURNAL OF CHEMICAL PHYSICS Koszinowski, K., Goldberg, N. T., Pomerantz, A. E., Zare, R. N., Juanes-Marcos, J. C., Althorpe, S. C. 2005; 123 (5)

    Abstract

    Product rotational distributions for the reaction H + D2 --> HD(nu'=1,j') + D have been measured for 16 collision energies in the range of 1.43 < or = E(coll) < or = 2.55 eV. Time-dependent quantum-mechanical calculations agree well in general with the experimental results, but they consistently yield slightly colder distributions. In terms of the average energy channeled into rotation, the differences between experiment and theory amount to approximately 10% for all collision energies sampled. No peculiarity is found for E(coll)=2.55 eV at which the system has sufficient energy to access the first HD2 electronically excited state.

    View details for DOI 10.1063/1.1978871

    View details for Web of Science ID 000231168700022

    View details for PubMedID 16108638

  • Enhanced proteolytic activity of covalently bound enzymes in photopolymerized sol gel. Analytical chemistry Dulay, M. T., Baca, Q. J., Zare, R. N. 2005; 77 (14): 4604-4610

    Abstract

    Trypsin is covalently linked to a photopolymerized sol-gel monolith modified by incorporating poly(ethylene glycol) (PSG-PEG) for on-column digestion of N(alpha)-benzoyl-l-arginine ethyl ester (BAEE) and two peptides, neurotensin and insulin chain B. The coupling of the enzyme to the monolith is via room-temperature Schiff chemistry in which an alkoxysilane reagent (linker) with an aldehyde functional group links to an inactive amine on trypsin to form an imine bond. The proteolytic activity of the immobilized trypsin was measured by monitoring the formation of N alpha-benzoyl-L-arginine (BA), the digestion product of BAEE. The BA is separated from BAEE by capillary electrophoresis and detected downstream (18.5 cm from the microreactor) by absorption (254 nm). Using the Bradford assay, we determined that 97 ng of trypsin is bound to the 1-cm microreactor located at the entrance of capillary column. The bioactivity of the trypsin-PSG-PEG microreactor at 20 degrees C for the digestion of BAEE was found to be 2270 units/mg of immobilized trypsin. The bioactivity of trypsin bound to the capillary wall in the open segment upstream from the monolith was 332 units/mg of immobilized trypsin under the same conditions. In contrast, the activity of free trypsin could not be observed for the digestion of BAEE at 20 degrees C after 16 h of incubation time.

    View details for PubMedID 16013879

  • Enhanced proteolytic activity enzymes in photopolymerized of covalently bound sol gel ANALYTICAL CHEMISTRY Dulay, M. T., Baca, Q. J., Zare, R. N. 2005; 77 (14): 4604-4610

    View details for DOI 10.1021/ac0504767

    View details for Web of Science ID 000230530300042

  • Correlated energy disposal and scattering dynamics of the Cl+CD4( v(3)=2) reaction MOLECULAR PHYSICS Bechtel, H. A., Kim, Z. H., Camden, J. P., Zare, R. N. 2005; 103 (13): 1837-1846

    View details for DOI 10.1080/00268970500044814

    View details for Web of Science ID 000229940900016

  • Peak height precision in Hadamard transform time-of-flight mass spectra JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Kimmel, J. R., Yoon, O. K., Zuleta, I. A., Trapp, O., Zare, R. N. 2005; 16 (7): 1117-1130

    View details for DOI 10.1016/j.jasms.2005.02.022

    View details for Web of Science ID 000230045500016

  • Extracts of impact breccia samples from Sudbury, Gardnos, and Ries impact craters and the effects of aggregation on C-60 detection GEOCHIMICA ET COSMOCHIMICA ACTA Elsila, J. E., de Leon, N. P., Plows, F. L., Buseck, P. R., Zare, R. N. 2005; 69 (11): 2891-2899

    View details for DOI 10.1016/j.gca.2004.11.023

    View details for Web of Science ID 000229759400014

  • Strange Fizzical Attraction - 2004 James Flack Norris Award, sponsored by the Northeastern Section of the ACS JOURNAL OF CHEMICAL EDUCATION Zare, R. N. 2005; 82 (5): 673-675

    View details for Web of Science ID 000228300200002

  • Effect of bin time on the photon counting histogram for one-photon excitation CHEMPHYSCHEM Perroud, T. D., Huang, B., Zare, R. N. 2005; 6 (5): 905-912

    Abstract

    We have demonstrated that our photon counting histogram (PCH) model with the correction for one-photon excitation is valid at multiple bin times. The fitted apparent brightness and concentration follow the three-dimensional diffusion model. More importantly, the semi-empirical parameter, F, introduced in the PCH model for one-photon excitation to correct for the non-Gaussian shape of the observation volume, shows small variations with different bin times. These variations are consistent with the physical interpretation of F, and they do not affect the resolving power of the PCH model for one-photon excitation. Based on these findings, we extend the time-independent PCH analysis to time-dependent photon counting multiple histograms (PCMH). This model considers the effect of bin time on the PCH parameters in a way that is similar to fluorescence intensity multiple distribution analysis (FIMDA). From the same set of data, PCMH extracts time-dependent parameters (diffusion time and triplet-state relaxation time) as well as time-independent parameters (true specific brightness and true average number of molecules). Given a three- to fourfold experimental difference in molecular brightness, we find that PCMH can resolve each species in a two-species sample and extract their respective diffusion times even when fluorescence correlation spectroscopy cannot.

    View details for DOI 10.1002/cphc.200400547

    View details for Web of Science ID 000229133300017

    View details for PubMedID 15884075

  • Evanescent-wave cavity ring-down investigation of polymer/solvent interactions JOURNAL OF PHYSICAL CHEMISTRY B Hannon, T. E., Chah, S. W., Zare, R. N. 2005; 109 (15): 7435-7442

    Abstract

    Evanescent-wave cavity ring-down spectroscopy (EW-CRDS) is used to measure interfacial phenomena when methanol or water is placed in contact with a film of poly(dimethylsiloxane) (PDMS), which is attached to the face of a fused-silica prism that constitutes part of a ring cavity. In the first few minutes after contact, the uptake of methanol is slower than that of water, but after this initial period the methanol diffuses more rapidly in the film than water does. Bulk weight-gain measurements confirm this result and yield diffusion coefficients of (25.1 +/- 0.7) x 10(-7) cm(2)/s for methanol in PDMS and (7 +/- 2) x 10(-7) cm(2)/s for water in PDMS. The interfacial optical losses found in the EW-CRDS measurements result primarily from scatter. In particular, we find that delamination of the film from the fused-silica substrate dominates the optical losses in the case of methanol. This conclusion is confirmed by separate surface plasmon resonance experiments.

    View details for DOI 10.1021/jp050045s

    View details for Web of Science ID 000228419100074

    View details for PubMedID 16851852

  • A soft on-column metal coating procedure for robust sheathless electrospray emitters used in capillary electrophoresis-mass spectrometry ELECTROPHORESIS Trapp, O., Pearce, E. W., Kimmel, J. R., Yoon, O. K., Zuleta, I. A., Zare, R. N. 2005; 26 (7-8): 1358-1365

    Abstract

    An on-column metal coating procedure was developed for sheathless electrospray emitters, based on Justus von Liebig's electroless silver mirror reaction followed by electrochemical deposition of gold onto the silver layer. The coating procedure is straightforward, mild, inexpensive, and can be performed with standard laboratory equipment. A long-term (600 h) stability investigation of the conductive coating was carried out by continuous electrospray in the positive electrospray mode, and no degradation in performance was found. The simplicity of the coating procedure and the robustness of the spray tips makes the spray tips highly suitable to couple delicate wall-coated or monolithic capillary columns to mass spectrometry. Peptide mixtures were separated by capillary electrophoresis and injected into either a Hadamard-transform time-of-flight mass analyzer or a commercial quadrupole mass analyzer using the described sheathless electrospray emitters. The performance was judged to be excellent.

    View details for DOI 10.1002/elps.200410152

    View details for Web of Science ID 000228784000009

    View details for PubMedID 15759300

  • Molecular orientation study of methylene blue at an air/fused-silica interface using evanescent-wave cavity ring-down spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Li, F. P., Zare, R. N. 2005; 109 (8): 3330-3333

    Abstract

    Using evanescent-wave cavity ring-down spectroscopy (EW-CRDS), we monitored the change in the absorbance of a thin film of methylene blue (MB) at an air/fused-silica interface while varying the polarization of the incident light (600 nm). We derived the average orientation angle of the planar MB molecules with respect to the surface normal and observed that the average orientation angle decreases as the surface concentration increases. At low surface concentrations, the MB molecules lie almost flat on the surface, whereas at higher surface concentrations the molecules become vertically oriented.

    View details for DOI 10.1021/jp045290a

    View details for Web of Science ID 000227247100037

    View details for PubMedID 16851361

  • Gold nanoparticles as a colorimetric sensor for protein conformational changes CHEMISTRY & BIOLOGY Chah, S., Hammond, M. R., Zare, R. N. 2005; 12 (3): 323-328

    Abstract

    Spherical gold nanoparticles and flat gold films are prepared in which yeast iso-1-cytochrome c (Cyt c) is covalently bound to the gold surface by a thiol group in the cystein 102 residue. Upon exposure to solutions of different pH, bound Cyt c unfolds at low pH and refolds at high pH. This conformational change causes measurable shifts in the color of the coated nanoparticle solutions detected by UV-VIS absorption spectroscopy and in the refractive index (RI) of the flat gold films detected by surface plasmon resonance (SPR) spectroscopy. Both experiments demonstrate the same trend with pH, suggesting the use of protein-covered gold nanoparticles as a simple colorimetric sensor for conformational change.

    View details for DOI 10.1016/j.chembiol.2005.01.013

    View details for Web of Science ID 000228260000011

    View details for PubMedID 15797216

  • Alkylation of polycyclic aromatic hydrocarbons in carbonaceous chondrites GEOCHIMICA ET COSMOCHIMICA ACTA Elsila, J. E., de Leon, N. P., Buseck, P. R., Zare, R. N. 2005; 69 (5): 1349-1357

    View details for DOI 10.1016/j.gca.2004.09.009

    View details for Web of Science ID 000227638900021

  • Effect of bending and torsional mode excitation on the reaction Cl+CH4 -> HCl+CH3 JOURNAL OF CHEMICAL PHYSICS Kim, Z. H., Bechtel, H. A., Camden, J. P., Zare, R. N. 2005; 122 (8)

    Abstract

    A beam containing CH(4), Cl(2), and He is expanded into a vacuum chamber where CH(4) is prepared via infrared excitation in a combination band consisting of one quantum of excitation each in the bending and torsional modes (nu(2)+nu(4)). The reaction is initiated by fast Cl atoms generated by photolysis of Cl(2) at 355 nm, and the resulting CH(3) and HCl products are detected in a state-specific manner using resonance-enhanced multiphoton ionization (REMPI). By comparing the relative amplitudes of the action spectra of Cl+CH(4)(nu(2)+nu(4)) and Cl+CH(4)(nu(3)) reactions, we determine that the nu(2)+nu(4) mode-driven reaction is at least 15% as reactive as the nu(3) (antisymmetric stretch) mode-driven reaction. The REMPI spectrum of the CH(3) products shows no propensity toward the formation of umbrella bend mode excited methyl radical, CH(3)(nu(2)=1), which is in sharp distinction to the theoretical expectation based on adiabatic correlations between CH(4) and CH(3). The rotational distribution of HCl(v=1) products from the Cl+CH(4)(nu(2)+nu(4)) reaction is hotter than the corresponding distribution from the Cl+CH(4)(nu(3)) reaction, even though the total energies of the two reactions are the same within 4%. An explanation for this enhanced rotational excitation of the HCl product from the Cl+CH(4)(nu(2)+nu(4)) reaction is offered in terms of the projection of the bending motion of the CH(4) reagent onto the rotational motion of the HCl product. The angular distributions of the HCl(nu=0) products from the Cl+CH(4)(nu(2)+nu(4)) reaction are backward scattered, which is in qualitative agreement with theoretical calculation. Overall, nonadiabatic product vibrational correlation and mode specificity of the reaction indicate that either the bending mode or the torsional mode or both modes are strongly coupled to the reaction coordinate.

    View details for DOI 10.1063/1.1844295

    View details for Web of Science ID 000227372200025

    View details for PubMedID 15836035

  • Moving beyond traditional UV-visible absorption detection: Cavity ring-down spectroscopy for HPLC ANALYTICAL CHEMISTRY Bechtel, K. L., Zare, R. N., Kachanov, A. A., Sanders, S. S., Paldus, B. A. 2005; 77 (4): 1177-1182

    Abstract

    We describe the use of liquid-phase continuous-wave cavity ring-down spectroscopy for the detection of an HPLC separation. This technique builds on earlier work by Snyder and Zare using pulsed laser sources and improves upon commercially available UV-visible detectors by a factor of up to 50. The system employs a compact doubled-diode single-mode continuous-wave laser operating at 488 nm and a previously described Brewster's-angle flow cell. Ring-down time constants as long as 5.8 micros were observed with liquid samples in a 0.3-mm path length cell. The baseline noise during an HPLC separation was only 2 x 10(-7) absorbance units (AU) peak to peak, as compared to 1 x 10(-5) AU for a state-of-the-art commercial UV-visible detector.

    View details for DOI 10.1021/ac048444r

    View details for Web of Science ID 000227111200031

    View details for PubMedID 15859003

  • Inductive behavior of electrolytes in AC conductance measurements CHEMICAL PHYSICS LETTERS Bardos, A., Zare, R. N., Markides, K. 2005; 402 (1-3): 274-278

    View details for DOI 10.1016/j.cplett.2004.12.047

    View details for Web of Science ID 000226479900052

  • Coating of poly(dimethylsiloxane) with n-dodecyl-beta-D-maltoside to minimize nonspecific protein adsorption LAB ON A CHIP Huang, B., Wu, H. K., Kim, S., Zare, R. N. 2005; 5 (10): 1005-1007

    Abstract

    Poly(dimethylsiloxane)(PDMS) surface is coated with n-dodecyl-beta-D-maltoside, which reduces the nonspecifically adsorbed protein on the PDMS surface to the single molecule level.

    View details for DOI 10.1039/b509251e

    View details for Web of Science ID 000232003200001

    View details for PubMedID 16175253

  • Plasma Diagnostics Non-Equilibrium Air Plasmas at Atmospheric Pressure Ganguly, B. N., Lampert, W. R., Akhtar, K., Scharer, J. E., Leipold, F., Laux, C. O., Zare, R. N., Yalin, A. P. edited by Becker, K. H., Kogelschatz, U., Schoenbach, K. H., Barker, R. J. Institute of Physics Publishing: Bristol. 2005: 446–536
  • Bursting Bubbles The Nucleus Zare, R. N. 2005; 83: 9-10
  • Construction of microfluidic chips using polydimethylsiloxane for adhesive bonding LAB ON A CHIP Wu, H. K., Huang, B., Zare, R. N. 2005; 5 (12): 1393-1398

    Abstract

    A thin layer of polydimethylsiloxane (PDMS) prepolymer, which is coated on a glass slide, is transferred onto the embossed area surfaces of a patterned substrate. This coated substrate is brought into contact with a flat plate, and the two structures are permanently bonded to form a sealed fluidic system by thermocuring (60 degrees C for 30 min) the prepolymer. The PDMS exists only at the contact area of the two surfaces with a negligible portion exposed to the microfluidic channel. This method is demonstrated by bonding microfluidic channels of two representative soft materials (PDMS substrate on a PDMS plate), and two representative hard materials (glass substrate on a glass plate). The effects of the adhesive layer on the electroosmotic flow (EOF) in glass channels are calculated and compared with the experimental results of a CE separation. For a channel with a size of approximately 10 to 500 microm, a approximately 200-500 nm thick adhesive layer creates a bond without voids or excess material and has little effect on the EOF rate. The major advantages of this bonding method are its generality and its ease of use.

    View details for DOI 10.1039/b510494g

    View details for Web of Science ID 000233276100009

    View details for PubMedID 16286971

  • Effects of bending excitation on the reaction of chlorine atoms with methane ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Bechtel, H. A., Camden, J. P., Brown, D. J., Martin, M. R., Zare, R. N., Vodopyanov, K. 2005; 44 (16): 2382-2385

    View details for DOI 10.1002/anie.200462837

    View details for Web of Science ID 000228709200016

    View details for PubMedID 15765488

  • Capillary electrophoretic and micellar electrokinetic separations of asymmetric dimethyl-L-arginine and structurally related amino acids: Quantitation in human plasma JOURNAL OF SEPARATION SCIENCE Trapp, G., Sydow, K., Dulay, M. T., Chou, T., Cooke, J. P., Zare, R. N. 2004; 27 (17-18): 1483-1490

    Abstract

    We report the development of efficient electrophoretic methods for the separation and quantification of L-arginine and six naturally occurring derivatives that are structurally and functionally related. Capillary electrophoresis (CE) employing a concentrated borate buffer at pH 9.4 achieves the separation of mixtures containing dimethyl-L-arginine, NG-monomethyl-L-arginine, L-arginine, L-homoarginine, L-ornithine, and L-citrulline as 4-fluoro-7-nitrobenzofurazan derivatives. In addition, the separation of the isomeric dimethyl-L-arginine derivatives (symmetric and asymmetric) is attained with baseline resolution by micellar electrokinetic chromatography (MEKC) when a high concentration of deoxycholic acid is added as a surfactant to the same running buffer. The influence of buffer type, concentration, and pH on the separation was studied to optimize separation conditions. The limit of quantitation (LOQ) for asymmetric dimethyl-L-arginine in aqueous solution was determined to be 20 microM using UV absorption in a CE separation and 0.1 microM using laser induced fluorescence (LIF) detection in an MEKC separation. This newly developed method was successfully applied for the quantitation of asymmetric dimethyl-L-arginine and L-arginine in human plasma samples at levels that might be used as a clinical diagnostic for cardiovascular disease (0.125 microM LOQ).

    View details for DOI 10.1002/jssc.200401918

    View details for Web of Science ID 000225938100011

    View details for PubMedID 15638156

  • Optical-optical double resonance photoionization spectroscopy of nf Rydberg states of nitric oxide JOURNAL OF CHEMICAL PHYSICS Zhao, R. C., Konen, I. M., Zare, R. N. 2004; 121 (20): 9938-9947

    Abstract

    The spectra of vibrationally excited nf Rydberg states of nitric oxide were recorded by monitoring the photoion current produced using two-photon double resonance excitation via the NO A (2)Sigma(+) state followed by photoexcitation of the Rydberg state that undergoes autoionization. The optical transition intensities from NO A state to nf Rydberg states were calculated, and the results agree closely with experiment. These results combined with circular dichroism measurements allow us to assign rotational quantum numbers to the nf Rydberg states even in a spectrum of relatively low resolution. We report the positions of these nf (upsilon,N,N(c)) Rydberg levels converging to the NO X (1)Sigma(+) upsilon(+) = 1 and 2 ionization limits where N is the total angular momentum excluding electron and nuclear spin and N(c) represents the rotational quantum number of the ion core. Our two-color optical-optical double resonance measurements cover the range of N from 15 to 28, N(c) from 14 to 29, and the principal quantum number n from 9 to 21. The electrostatic interaction between the Rydberg electron and the ion core is used to account for the rotational fine structure and a corresponding model is used to fit the energy levels to obtain the quadrupole moment and polarizability of the NO(+) core. Comparison with a multichannel quantum defect theory fit to the same data confirms that the model we use for the electrostatic interaction between the nf Rydberg electron and the ion core of NO well describes the rotational fine structure.

    View details for DOI 10.1063/1.1807373

    View details for Web of Science ID 000225042700020

    View details for PubMedID 15549868

  • Photon counting histogram: One-photon excitation CHEMPHYSCHEM Huang, B., Perroud, T. D., Zare, R. N. 2004; 5 (10): 1523-1531

    Abstract

    The photon counting histogram (PCH) analysis is a fluorescence fluctuation method that is able to characterize the brightness and concentration of different fluorescent species present in a liquid sample. We find that the PCH model using a three-dimensional Gaussian observation volume profile is inadequate for fitting experimental data obtained from a confocal setup with one-photon excitation. We propose an imoroved model, which is based on the correction to the observation volume profile for the out-of-focus emission. We demonstrate that this model is able to resolve different species present under a wide range of conditions. Attention is given to how this model allows the examination of the effects of different instrumental setups on the resolvability.

    View details for DOI 10.1002/cphc.200400176

    View details for Web of Science ID 000224692100008

    View details for PubMedID 15535551

  • Rovibrational product state distribution for inelastic H+D-2 collisions JOURNAL OF CHEMICAL PHYSICS Pomerantz, A. E., Ausfelder, F., Zare, R. N., Juanes-Marcos, J. C., Althorpe, S. C., Rabanos, V. S., Aoiz, F. J., Banares, L., Castillo, J. F. 2004; 121 (14): 6587-6590

    Abstract

    Experimental measurements of rovibrational product state distributions for the inelastic scattering process H + D2(nu=0,j)-->H + D2(nu' = 1,2,j') are presented and compared with the results of quasiclassical and quantum mechanical calculations. Agreement between theory and experiment is almost quantitative. Two subtle trends are found: the relative amount of energy in product rotational excitation decreases slightly with increasing collision energy and increases slightly with increasing product vibrational excitation. These trends are the reverse of what has been found for reactive scattering in which the opposite trends are much more pronounced.

    View details for DOI 10.1063/1.1804940

    View details for Web of Science ID 000224269200001

    View details for PubMedID 15473712

  • Probing excited electronic states using vibrationally mediated photolysis: Application to hydrogen iodide JOURNAL OF PHYSICAL CHEMISTRY A Camden, J. P., Bechtel, H. A., Brown, D. J., Pomerantz, A. E., Zare, R. N., Le Roy, R. J. 2004; 108 (39): 7806-7813

    View details for DOI 10.1021/jp49051z

    View details for Web of Science ID 000224071600006

  • Application of ion chromatography to the investigation of real-world samples JOURNAL OF CHEMICAL EDUCATION Whelan, R. J., Hannon, T. E., Zare, R. N., Rakestraw, D. J. 2004; 81 (9): 1299-1302

    View details for Web of Science ID 000223203100015

  • Chemical cytometry on a picoliter-scale integrated microfluidic chip PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Wu, H. K., Wheeler, A., Zare, R. N. 2004; 101 (35): 12809-12813

    Abstract

    An integrated microfluidic device has been fabricated for analyzing the chemical contents of a single cell (chemical cytometry). The device is designed to accomplish four different functions: (i) cell handling, (ii) metering and delivering of chemical reagents, (iii) cell lysis and chemical derivatization, and (iv) separating derivatized compounds and detecting them by laser-induced fluorescence. These functions are accomplished with only two valves, formed by multilayer soft lithography. A new kind of three-state valve and a picopipette are described; these elements are crucial for minimizing the reaction volume and ensuring optimal shape of the channel for electrophoresis injection. By using these valves, a reaction volume of approximately 70 pl is achieved for the lysis and derivitization of the contents of a single Jurkat T cell (approximately 10 microm diameter). As a demonstration of the use of this integrated microfluidic device, electropherograms of amino acids from individual Jurkat T cells are recorded and compared with those collected from a multiple-cell homogenate.

    View details for DOI 10.1073/pnas.0405299101

    View details for Web of Science ID 000223694700008

    View details for PubMedID 15328405

    View details for PubMedCentralID PMC516477

  • Walk-off ring-down spectroscopy: attaining ultrafast resolution by converting time into space 18th Colloquium on High Resolution Molecular Spectroscopy Rypkema, H. A., Martin, M. R., Zare, R. N. TAYLOR & FRANCIS LTD. 2004: 1501–8

    View details for DOI 10.1080/00268970410001725819

    View details for Web of Science ID 000225105500002

  • Line strength factors for E,F-1 Sigma(+)(g)(v '=0, J '=J '')-X-1 Sigma(+)(g) (v '', J '') (2+1) REMPI transitions in molecular hydrogen CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE Pomerantz, A. E., Ausfelder, F., Zare, R. N., Huo, W. M. 2004; 82 (6): 723-729

    View details for DOI 10.1139/V04-074

    View details for Web of Science ID 000224450700007

  • Surface plasmon resonance analysis of aqueous mercuric ions SENSORS AND ACTUATORS B-CHEMICAL Chah, S., Yi, J. H., Zare, R. N. 2004; 99 (2-3): 216-222

    View details for DOI 10.1016/j.snb.2003.11.015

    View details for Web of Science ID 000221580100003

  • Factors affecting quantitative analysis in laser desorption/laser ionization mass spectrometry ANALYTICAL CHEMISTRY Elsila, J. E., de Leon, N. P., Zare, R. N. 2004; 76 (9): 2430-2437

    Abstract

    Microprobe laser desorption/laser ionization mass spectrometry (microL(2)MS) is a sensitive and selective technique that has proven useful in the qualitative and semiquantitative detection of trace organic compounds, particularly polycyclic aromatic hydrocarbons (PAHs). Recent efforts have focused on developing microL(2)MS as a quantitative method, often by measuring the ratio of signal strength of an analyte to an internal standard. Here, we present evidence of factors that affect these ratios and thus create uncertainty and irreproducibility in quantification. The power and wavelength of the desorption laser, the delay time between the desorption and ionization steps, the power of the ionization laser, and the ionization laser alignment are all shown to change PAH ratios, in some cases by up to a factor of 24. Although changes in the desorption laser parameters and the delay time cause the largest effects, the ionization laser power and alignment are the most difficult parameters to control and thus provide the most practical limitations for quantitative microL(2)MS. Variation in ratios is seen in both synthetic poly(vinyl chloride) membranes and in "real-life" samples of Murchison meteorite powder. Ratios between similar PAHs vary less than those between PAHs that differ greatly in mass and structure. This finding indicates that multiple internal standards may be needed for quantification of samples containing diverse PAHs.

    View details for DOI 10.1021/ac0354140

    View details for Web of Science ID 000221205900010

    View details for PubMedID 15117180

  • Electroosmotic flow in a poly(dimethylsiloxane) channel does not depend on percent curing agent ELECTROPHORESIS Wheeler, A. R., Trapp, G., Trapp, O., Zare, R. N. 2004; 25 (7-8): 1120-1124

    Abstract

    Poly(dimethylsiloxane) (PDMS) microfluidic devices were prepared from different ratios of "curing agent" (which contains silicon hydride groups) to "base" (which contains vinyl-terminated noncross-linked PDMS), to determine the effect of this ratio on electroosmotic flow (EOF). In fabricating devices for this purpose, a novel method for permanently enclosing PDMS channels was developed. As a supplement to the microfluidic method, the inner walls of capillaries were coated with PDMS formed from varying ratios of curing agent to base. EOF was found to be constant for PDMS formed with each ratio, which implies that the negative surface charges do not arise from chemical species present only in the base or the curing agent.

    View details for DOI 10.1002/elps.200305784

    View details for Web of Science ID 000221168700024

    View details for PubMedID 15095455

  • Integration of on-line protein digestion, peptide separation, and protein identification using pepsin-coated photopolymerized sol-gel columns and capillary electrophoresis/mass spectrometry ANALYTICAL CHEMISTRY Kato, M., Sakai-Kato, K., Jin, H. M., Kubota, K., Miyano, H., Toyo'oka, T., Dulay, M. T., Zare, R. N. 2004; 76 (7): 1896-1902

    Abstract

    A miniaturized pepsin reactor was prepared inside a fused-silica capillary (i.d. 75 microm) by coating a pepsin-containing gel on a photopolymerized porous silica monolith. The pepsin-encapsulated film was prepared by a sol-gel method. The sol-gel reaction was optimized so that the sol solution containing pepsin forms a thin film on the photopolymerized sol-gel (PSG) monolith that was initially fabricated at the inlet of the capillary. Pepsin was encapsulated into the gel matrix without losing its activity. The large surface area of the PSG monolith enabled the immobilized pepsin to achieve a high catalytic turnover rate, and the porous nature of the PSG promotes penetration of large molecular proteins into the column. The immobilized pepsin-digested peptides and proteins, and the resulting mixture of peptide fragments, could be directly separated in the portion of the capillary where no PSG monolith exists. The durability and repeatability of the fabricated pepsin-coated column was tested and found to be satisfactory. An acidic solution consisting of 0.5 M formic acid was used as the running buffer, because it suppresses the adsorption of proteins or peptides on the inner surface of the capillary as well as enables direct connection of the output of the capillary electrophoresis column to a mass spectrometer. The on-line digestion of insulin chain beta and lysozyme provides identification of the proteolytic peptides. Recovery was achieved for 100% of the insulin chain beta amino acid sequence and 73% of the lysozyme amino acid sequence.

    View details for DOI 10.1021/ac035107u

    View details for Web of Science ID 000220618400022

    View details for PubMedID 15053649

  • Denaturation and renaturation of self-assembled yeast iso-1-cytochrome c on Au ANALYTICAL CHEMISTRY Chah, S., Kumar, C. V., Hammond, M. R., Zare, R. N. 2004; 76 (7): 2112-2117

    Abstract

    We have made surface plasmon resonance (SPR) measurements of yeast iso-1-cytochrome c (Cyt c) on a gold surface. Angle-resolved SPR curves are recorded as a function of urea concentration before and after self-assembly of the Cyt c. Exposure to a urea solution causes denaturation of Cyt c, which shifts the minimum in the SPR curve to a larger angle and decreases the signal amplitude. The Gibbs free energy change for denaturation of the protein on Au is calculated from the change of the SPR signal amplitude with urea concentration. We find that (1) Cyt c can be reversibly denatured and renatured, depending on the urea concentration, and (2) the Gibbs free energy change for denaturation of Cyt c on Au surface in water, DeltaG degrees (water), is 1.5 kcal/mol, which is approximately 4 times less than that in bulk solution.

    View details for DOI 10.1021/ac035416k

    View details for Web of Science ID 000220618400050

    View details for PubMedID 15053677

  • Laboratory experiments of Titan tholin formed in cold plasma at various pressures: implications for nitrogen-containing polycyclic aromatic compounds in Titan haze ICARUS Imanaka, H., Khare, B. N., Elsila, J. E., Bakes, E. L., McKay, C. P., Cruikshank, D. P., Sugita, S., Matsui, T., Zare, R. N. 2004; 168 (2): 344-366

    View details for DOI 10.1016/j.icarus.2003.12.014

    View details for Web of Science ID 000220474300011

  • Poly(dimethylsiloxane) microfluidic flow cells for surface plasmon resonance spectroscopy SENSORS AND ACTUATORS B-CHEMICAL Wheeler, A. R., Chah, S., Whelan, R. J., Zare, R. N. 2004; 98 (2-3): 208-214

    View details for DOI 10.1016/j.snb.2003.06.004

    View details for Web of Science ID 000220214300014

  • Comparing the dynamical effects of symmetric and antisymmetric stretch excitation of methane in the Cl+CH4 reaction JOURNAL OF CHEMICAL PHYSICS Bechtel, H. A., Camden, J. P., Brown, D. J., Zare, R. N. 2004; 120 (11): 5096-5103

    Abstract

    The effects of two nearly isoenergetic C-H stretching motions on the gas-phase reaction of atomic chlorine with methane are examined. First, a 1:4:9 mixture of Cl(2), CH(4), and He is coexpanded into a vacuum chamber. Then, either the antisymmetric stretch (nu(3)=3019 cm(-1)) of CH(4) is prepared by direct infrared absorption or the infrared-inactive symmetric stretch (nu(1)=2917 cm(-1)) of CH(4) is prepared by stimulated Raman pumping. Photolysis of Cl(2) at 355 nm generates fast Cl atoms that initiate the reaction with a collision energy of 1290+/-175 cm(-1) (0.16+/-0.02 eV). Finally, the nascent HCl or CH(3) products are detected state-specifically via resonance enhanced multiphoton ionization and separated by mass in a time-of-flight spectrometer. We find that the rovibrational distributions and state-selected differential cross sections of the HCl and CH(3) products from the two vibrationally excited reactions are nearly indistinguishable. Although Yoon et al. [J. Chem. Phys. 119, 9568 (2003)] report that the reactivities of these two different types of vibrational excitation are quite different, the present results indicate that the reactions of symmetric-stretch excited or antisymmetric-stretch excited methane with atomic chlorine follow closely related product pathways. Approximately 37% of the reaction products are formed in HCl(v=1,J) states with little rotational excitation. At low J states these products are sharply forward scattered, but become almost equally forward and backward scattered at higher J states. The remaining reaction products are formed in HCl(v=0,J) and have more rotational excitation. The HCl(v=0,J) products are predominantly back and side scattered. Measurements of the CH(3) products indicate production of a non-negligible amount of umbrella bend excited methyl radicals primarily in coincidence with the HCl(v=0,J) products. The data are consistent with a model in which the impact parameter governs the scattering dynamics.

    View details for DOI 10.1063/1.1647533

    View details for Web of Science ID 000220225000014

    View details for PubMedID 15267378

  • State-to-state dynamics of the Cl+CH3OH -> HCl+CH2OH reaction JOURNAL OF CHEMICAL PHYSICS Bechtel, H. A., Camden, J. P., Zare, R. N. 2004; 120 (9): 4231-4239

    Abstract

    Molecular chlorine, methanol, and helium are co-expanded into a vacuum chamber using a custom designed "late-mixing" nozzle. The title reaction is initiated by photolysis of Cl2 at 355 nm, which generates monoenergetic Cl atoms that react with CH3OH at a collision energy of 1960 +/- 170 cm(-1) (0.24 +/- 0.02 eV). Rovibrational state distributions of the nascent HCl products are obtained via 2 + 1 resonance enhanced multiphoton ionization, center-of-mass scattering distributions are measured by the core-extraction technique, and the average internal energy of the CH3OH co-products is deduced by measuring the spatial anisotropy of the HCl products. The majority (84 +/- 7%) of the HCl reaction products are formed in HCl(v = 0) with an average rotational energy of [Erot] = 390 +/- 70 cm(-1). The remaining 16 +/- 7% are formed in HCl(v = 1) and have an average rotational energy of [Erot] = 190 +/- 30 cm(-1). The HCl(v = 1) products are primarily forward scattered, and they are formed in coincidence with CH2OH products that have little internal energy. In contrast, the HCl(v = 0) products are formed in coincidence with CH2OH products that have significant internal energy. These results indicate that two or more different mechanisms are responsible for the dynamics in the Cl + CH3OH reaction. We suggest that (1) the HCl(v = 1) products are formed primarily from collisions at high impact parameter via a stripping mechanism in which the CH2OH co-products act as spectators, and (2) the HCl(v = 0) products are formed from collisions over a wide range of impact parameters, resulting in both a stripping mechanism and a rebound mechanism in which the CH2OH co-products are active participants. In all cases, the reaction of fast Cl atoms with CH3OH is with the hydrogen atoms on the methyl group, not the hydrogen on the hydroxyl group.

    View details for DOI 10.1063/1.1644797

    View details for Web of Science ID 000189209200020

    View details for PubMedID 15268590

  • Collision energy dependence of the HD(nu(')=2) product rotational distribution of the H+D-2 reaction in the range 1.30-1.89 eV JOURNAL OF CHEMICAL PHYSICS Ausfelder, F., Pomerantz, A. E., Zare, R. N., Althorpe, S. C., Aoiz, F. J., Banares, L., Castillo, J. F. 2004; 120 (7): 3255-3264

    Abstract

    An experimental and theoretical investigation of the collision energy dependence of the HD(nu' = 2,j') rotational product state distribution for the H + D2 reaction in the collision energy range of Ecol = 1.30-1.89 eV has been carried out. Theoretical results based on time-dependent and time-independent quantum mechanical methods agree nearly perfectly with each other, and the agreement with the experiment is good at low collision energies and very good at high collision energies. This behavior is in marked contrast to a previous report on the HD(nu' = 3,j') product state rotational distribution [Pomerantz et al., J. Chem. Phys. 120, 3244 (2004)] where a systematic difference between experiment and theory was observed, especially at the highest collision energies. The reason for this different behavior is not yet understood. In addition, this study employs Doppler-free spectroscopy to resolve an ambiguity in the E, F-X resonantly enhanced multiphoton ionization transition originating from the HD(nu' = 2,j' = 1) state, which is found to be caused by an accidental blending with the transition coming from the HD(nu' = 1,j' = 14) state.

    View details for DOI 10.1063/1.1641009

    View details for Web of Science ID 000188880900025

    View details for PubMedID 15268479

  • Disagreement between theory and experiment in the simplest chemical reaction: Collision energy dependent rotational distributions for H+D-2 -> HD(nu(')=3,j('))+D JOURNAL OF CHEMICAL PHYSICS Pomerantz, A. E., Ausfelder, F., Zare, R. N., Althorpe, S. C., Aoiz, F. J., Banares, L., Castillo, J. F. 2004; 120 (7): 3244-3254

    Abstract

    We present experimental rotational distributions for the reaction H + D2 --> HD(nu' = 3,j') + D at eight different collision energies between 1.49 and 1.85 eV. We combine a previous measurement of the state-resolved excitation function for this reaction [Ayers et al., J. Chem. Phys. 119, 4662 (2003)] with the current data to produce a map of the relative reactive cross section as a function of both collision energy and rotational quantum number (an E-j' plot). To compare with the experimental data, we also present E-j' plots resulting from both time-dependent and time-independent quantum mechanical calculations carried out on the BKMP2 surface. The two calculations agree well with each other, but they produce rotational distributions significantly colder than the experiment, with the difference being more pronounced at higher collision energies. Disagreement between theory and experiment might be regarded as surprising considering the simplicity of this system; potential causes of this discrepancy are discussed.

    View details for DOI 10.1063/1.1641008

    View details for Web of Science ID 000188880900024

    View details for PubMedID 15268478

  • Design and characterization of a late-mixing pulsed nozzle REVIEW OF SCIENTIFIC INSTRUMENTS Camden, J. P., Bechtel, H. A., Zare, R. N. 2004; 75 (2): 556-558

    View details for DOI 10.1063/1.1641158

    View details for Web of Science ID 000188532400043

  • Bond and mode selectivity in the reaction of atomic chlorine with vibrationally excited CH2D2 JOURNAL OF CHEMICAL PHYSICS Bechtel, H. A., Kim, Z. H., Camden, J. P., Zare, R. N. 2004; 120 (2): 791-799

    Abstract

    The title reaction is investigated by co-expanding a mixture of Cl2 and CH2D2 into a vacuum chamber and initiating the reaction by photolyzing Cl2 with linearly polarized 355 nm light. Excitation of the first C-H overtone of CH2D2 leads to a preference for hydrogen abstraction over deuterium abstraction by at least a factor of 20, whereas excitation of the first C-D overtone of CH2D2 reverses this preference by at least a factor of 10. Reactions with CH2D2 prepared in a local mode containing two quanta in one C-H oscillator /2000>- or in a local mode containing one quantum each in two C-H oscillators /1100> lead to products with significantly different rotational, vibrational, and angular distributions, although the vibrational energy for each mode is nearly identical. The Cl+CH2D2/2000>- reaction yields methyl radical products primarily in their ground state, whereas the Cl+CH2D2/1100> reaction yields methyl radical products that are C-H stretch excited. The HCl(v=1) rotational distribution from the Cl+CH2D2/2000>- reaction is significantly hotter than the HCl(v=1) rotational distribution from the Cl+CH2D2/1100> reaction, and the HCl(v=1) differential cross-section (DCS) of the Cl+CH2D2/2000>- reaction is more broadly side scattered than the HCl(v=1) DCS of the Cl+CH2D2/1100> reaction. The results can be explained by a simple spectator model and by noting that the /2000>- mode leads to a wider cone of acceptance for the reaction than the /1100> mode. These measurements represent the first example of mode selectivity observed in a differential cross section, and they demonstrate that vibrational excitation can be used to direct the reaction pathway of the Cl+CH2D2 reaction.

    View details for DOI 10.1063/1.1630961

    View details for Web of Science ID 000187718200031

    View details for PubMedID 15267915

  • Continuous two-channel time-of-flight mass spectrometric detection of electrosprayed ions ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Trapp, O., Kimmel, J. R., Yoon, O. K., Zuleta, I. A., Fernandez, F. M., Zare, R. N. 2004; 43 (47): 6541-6544

    View details for DOI 10.1002/anie.200461240

    View details for Web of Science ID 000225718700026

    View details for PubMedID 15578763

  • Fizzical Attraction Nature Zare, R. N. 2004; 432: 954
  • An evolutionary connection between interstellar ices and IDPs? Clues from mass spectroscopy measurements of laboratory simulations 2nd World Space Congress/34th COSPAR Scientific Assembly Dworkin, J. P., Gillette, J. S., Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Elsila, J. E., McGlothlin, D. R., Zare, R. N. PERGAMON-ELSEVIER SCIENCE LTD. 2004: 67–71

    View details for DOI 10.1016/j.asr.2003.08.004

    View details for Web of Science ID 000189505400009

  • Photon counting histogram for one-photon excitation (vol 4, pg 1121, 2003) CHEMPHYSCHEM Perroud, T. D., Huang, B., Wallace, M. I., Zare, R. N. 2003; 4 (12): 1280-1280

    View details for Web of Science ID 000187663800001

  • Single-cell immunosensors for protein detection BIOSENSORS & BIOELECTRONICS Whelan, R. J., Zare, R. N. 2003; 19 (4): 331-336

    Abstract

    A single-cell detector is described that combines the natural signal amplification of whole-cell biosensors with the flexibility and specificity of immunological recognition. An immune cell that expresses receptors for the constant region of immunoglobulin G (IgG) is loaded with a Ca(2+)-indicating dye and with antibodies directed against the protein of interest. Introduction of a multivalent protein antigen causes cross-linking of the receptors, which results in a detectable increase in the concentration of cytosolic Ca(2+). Some immune cell lines respond to stimulation with oscillations in their cytosolic Ca(2+) levels that complicate their use as detectors. The human monocytic cell line U-937, when treated with the cytokine interferon-gamma, produces a large, short-lived Ca(2+) signal in response to cross-linking of its high-affinity IgG receptors. U-937 was therefore chosen for development as an immunity-based detector. Human and rabbit antibodies are found to effectively stimulate the cell, causing a prompt and transient response. The cell is able to respond to repeated stimulation, though the response diminishes during rapid stimulation. Ovalbumin can be detected in micromolar concentrations. Possible fundamental constraints on the size of a detectable analyte are discussed.

    View details for DOI 10.1016/S0956-5663(03)00190-8

    View details for Web of Science ID 000186918900008

    View details for PubMedID 14615091

  • Photon counting histogram for one-photon excitation CHEMPHYSCHEM Perroud, T. D., Huang, B., Wallace, M. I., Zare, R. N. 2003; 4 (10): 1121-1123

    View details for DOI 10.1002/cphc.200300824

    View details for Web of Science ID 000186151200016

    View details for PubMedID 14596014

  • Reflections on the development of Laboratory instrumentation AMERICAN LABORATORY Howard, B., Stevenson, R., Abramowitz, M., Avdalovic, N., Bidlingmeyer, B. A., Coates, J., Ettre, L., Finnigan, R. E., Gooding, K., Hancock, W., Hobbs, J., Hoehn, D., Jinno, K., Middaugh, C. R., Patel, P., Nalepa, R., Olesik, S. V., Raynie, D., Sands, A., Shuett, L. C., Slavin, W., Smallcombe, S., Wilkinson, G., Willis, B. G., Zare, R. N., Zhang, Y. K. 2003; 35 (20): 24-?

    View details for Web of Science ID 000186357100006

  • Measurement of the cross section for H+D-2 -> HD(v(')=3,j '=0)+D as a function of angle and energy JOURNAL OF CHEMICAL PHYSICS Ayers, J. D., Pomerantz, A. E., Fernandez-Alonso, F., Ausfelder, F., Bean, B. D., Zare, R. N. 2003; 119 (9): 4662-4670

    View details for DOI 10.1063/1.1595092

    View details for Web of Science ID 000184775200007

  • PAH sorption mechanism and partitioning behavior in lampblack-impacted soils from former oil-gas plant sites ENVIRONMENTAL SCIENCE & TECHNOLOGY Hong, L., Ghosh, U., Mahajan, T., Zare, R. N., Luthy, R. G. 2003; 37 (16): 3625-3634

    Abstract

    This study assessed polycyclic aromatic hydrocarbon (PAH) association and aqueous partitioning in lampblack-impacted field soils from five sites in California that formerly housed oil-gas process operations. Lampblack is the solid residue resulting from the decomposition of crude oil at high temperatures in the gas-making operation and is coated or impregnated with oil gasification byproducts, among which PAHs are the compounds of the greatest regulatory concern. A suite of complementary measurements investigated the character of lampblack particles and PAH location and the associated effects on PAH partitioning between lampblack and water. PAH analyses on both whole samples and density-separated components demonstrated that 81-100% of PAHs in the lampblack-impacted soils was associated with lampblack particles. FTIR, 13C NMR, and SEM analyses showed that oil-gas lampblack solids comprise primarily aromatic carbon with soot-like structures. A free-phase aromatic oil may be present in some of the lampblack soils containing high PAH concentrations. Comparable long-term aqueous partitioning measurements were obtained with an air-bridge technique and with a centrifugation/alum flocculation procedure. Large solid/water partition coefficient (Kd) values were observed in samples exhibiting lower PAH and oil levels, whereas smaller Kd values were measured in lampblack samples containing high PAH levels. The former result is in agreement with an oil-soot partitioning model, and the latter is in agreement with a coal tar-water partitioning model. Lampblack containing high PAH levels appears to exhaust the sorption capacity of the soot-carbon, creating a free aromatic oil phase that exhibits partitioning behavior similar to PAHs in coal tar. This study improves mechanistic understanding of PAH sorption on aged lampblack residuals at former oil-gas sites and provides a framework for mechanistic assessment of PAH leaching potential and risk from such site materials.

    View details for DOI 10.1021/es0262683

    View details for Web of Science ID 000184803700022

    View details for PubMedID 12953875

  • Teaching effective communication in a writing-intensive analytical chemistry course JOURNAL OF CHEMICAL EDUCATION Whelan, R. J., Zare, R. N. 2003; 80 (8): 904-906

    View details for Web of Science ID 000184143500010

  • Adsorption of crystal violet to the silica-water interface monitored by evanescent wave cavity ring-down spectroscopy JOURNAL OF PHYSICAL CHEMISTRY B Shaw, A. M., Hannon, T. E., Li, F. P., Zare, R. N. 2003; 107 (29): 7070-7075

    View details for DOI 10.1021/jp027636s

    View details for Web of Science ID 000184242600022

  • Microfluidic device for single-cell analysis ANALYTICAL CHEMISTRY Wheeler, A. R., Throndset, W. R., Whelan, R. J., Leach, A. M., Zare, R. N., Liao, Y. H., Farrell, K., Manger, I. D., Daridon, A. 2003; 75 (14): 3581-3586

    Abstract

    We have developed a novel microfluidic device constructed from poly(dimethylsiloxane) using multilayer soft lithography technology for the analysis of single cells. The microfluidic network enables the passive and gentle separation of a single cell from the bulk cell suspension, and integrated valves and pumps enable the precise delivery of nanoliter volumes of reagents to that cell. Various applications are demonstrated, including cell viability assays, ionophore-mediated intracellular Ca2+ flux measurements, and multistep receptor-mediated Ca2+ measurements. These assays, and others, are achieved with significant improvements in reagent consumption, analysis time, and temporal resolution over macroscale alternatives.

    View details for DOI 10.1021/ac0340758

    View details for Web of Science ID 000184649500041

    View details for PubMedID 14570213

  • Determination of glutamine and serine in rat cerebrospinal fluid using capillary electrochromatography with a modified photopolymerized sol-gel monolithic column JOURNAL OF CHROMATOGRAPHY A Kato, M., Jin, H. M., Sakai-Kato, K., Toyo'oka, T., Dulay, M. T., Zare, R. N. 2003; 1004 (1-2): 209-215

    Abstract

    Capillary electrochromatographic separations of amino acid mixtures were studied using two modified porous photopolymerized sol-gel monolithic columns. One was modified with dimethyloctadecylchlorosilane (DMOS), and the other was modified with DMOS, followed by chlorotrimethylsilane to end-cap residual silanol groups. Prior to separation, amino acids were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole using as a mobile phase 50 mM phosphate (pH 2.5), water, and acetonitrile in the ratio of 1:1:8. Five derivatized amino acids (Asn, Phe, Ala, Ile, and Leu) were separated within 7 min. Theoretical plate numbers varied between 58700 and 105000/m. This separation method with the end-capped monolithic column was applied to rat cerebrospinal fluid. The dominant amino acid found was Gln at a concentration of 420 microM along with small quantities of Ser (54 microM).

    View details for DOI 10.1016/S0021-9673(03)00451-5

    View details for Web of Science ID 000184296600023

    View details for PubMedID 12929975

  • Cavity ring-down spectroscopy as a detector for liquid chromatography ANALYTICAL CHEMISTRY Snyder, K. L., Zare, R. N. 2003; 75 (13): 3086-3091

    Abstract

    We have demonstrated the use of cavity ring-down spectroscopy (CRDS) as a detector for high performance liquid chromatography (HPLC). For this use, we have designed and implemented a Brewster's angle flow cell such that cavity ring-down spectroscopy can be performed on microliter volumes of liquids. The system exhibits a linear dynamic range of 3 orders of magnitude (30 nM to 30 microM quinalizarin at 470 nm) for static measurements and 2 orders of magnitude (0.5 microM to 50 microM) for HPLC measurements. For the static measurements, the baseline noise is 2.8 x 10(-6) AU rms and 1.0 x 10(-5) AU peak-to-peak, and for the HPLC separations, it is 3.2 x 10(-6) AU rms and 1.3 x 10(-5) AU peak-to-peak. The baseline noise is determined after the data are smoothed by an 11-point boxcar average. The peak areas detected from HPLC separations are reproducible to within 2-3%. The HPLC mass detection limit for a molecule with epsilon = 9 x 10(3) M(-1) cm(-1) in a 300-microm path length cell (illuminated volume, 0.5 microL) is reported as 2.5 x 10(-8) g/mL. These results were obtained using a simple pulsed CRDS system and are comparable to, if not better than, a high-quality commercial UV-vis absorption detector for the same path length.

    View details for DOI 10.1021/ac0340152

    View details for Web of Science ID 000183975300026

    View details for PubMedID 12964755

  • Photodissociation of O-2 via the Herzberg continuum: Measurements of O-atom alignment and orientation JOURNAL OF CHEMICAL PHYSICS Alexander, A. J., Kim, Z. H., Zare, R. N. 2003; 118 (23): 10566-10574

    View details for DOI 10.1063/1.1574511

    View details for Web of Science ID 000183124300023

  • Optical diagnostics of atmospheric pressure air plasmas PLASMA SOURCES SCIENCE & TECHNOLOGY Laux, C. O., Spence, T. G., Kruger, C. H., Zare, R. N. 2003; 12 (2): 125-138

    View details for Web of Science ID 000183461900001

  • Use of broadband, continuous-wave diode lasers in cavity ring-down spectroscopy for liquid samples APPLIED SPECTROSCOPY Hallock, A. J., Berman, E. S., Zare, R. N. 2003; 57 (5): 571-573

    Abstract

    Cavity ring-down spectroscopy (CRDS) is an extremely sensitive absorption technique that has been applied primarily to gas samples, which are characterized by having narrow absorption features. Recently, CRDS has also been applied to liquid samples, which have broad absorption features. The use of small inexpensive diode lasers as light sources for liquid samples is demonstrated. The low cost coupled with the ease and technical straightforwardness of application gives this technique wide appeal.

    View details for Web of Science ID 000184358400016

    View details for PubMedID 14658685

  • Evidence that polycyclic aromatic hydrocarbons in two carbonaceous chondrites predate parent-body formation GEOCHIMICA ET COSMOCHIMICA ACTA Plows, F. L., Elsila, J. E., Zare, R. N., Buseck, P. R. 2003; 67 (7): 1429-1436

    View details for DOI 10.1016/S0016-7037(02)01277-2

    View details for Web of Science ID 000181734000013

  • Surface plasmon resonance detection for capillary electrophoresis separations ANALYTICAL CHEMISTRY Whelan, R. J., Zare, R. N. 2003; 75 (6): 1542-1547

    Abstract

    A miniaturized surface plasmon resonance sensor has been used as an on-line detector for capillary electrophoresis separations. The capillary was modified slightly to shield the sensor electronics from the high voltages applied during the separation. A three-component mixture of high refractive index materials was separated and detected at the millimolar level by an untreated gold-sensing surface. A simple protein immobilization procedure was used to functionalize the surface for selective protein detection. A hybrid buffer system was developed, in which both the deposition of immobilized protein layers and the electrophoretic delivery of protein analytes were optimized. The detection system has a reproducibility of 15%, a dynamic range of 3 orders of magnitude, and a detection limit for IgG of 2 fmol.

    View details for DOI 10.1021/ac0263521

    View details for Web of Science ID 000181675900042

    View details for PubMedID 12659220

  • Doppler-free multi-photon ionization: a proposal for enhancing ion images CHEMICAL PHYSICS LETTERS Pomerantz, A. E., Zare, R. N. 2003; 370 (3-4): 515-521

    View details for DOI 10.1016/S0009-2614(03)00158-1

    View details for Web of Science ID 000181386600034

  • Effects of modulation defects on Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Kimmel, J. R., Fernandez, F. M., Zare, R. N. 2003; 14 (3): 278-286

    Abstract

    In any Hadamard multiplexing technique, discrepancies between the intended and the applied encoding sequences may reduce the intensity of real spectral features and create discrete, artificial signals. In our implementation of Hadamard transform time-of-flight mass spectrometry (HT-TOFMS), the encoding sequence is applied to the ion beam by means of an interleaved comb of wires (Bradbury-Nielson gate), which shutters the ion beam on and off. By isolating and exaggerating individual skewing effects in simulating the HT-TOFMS process, we determined the nature of errors that arise from various defects. In particular, we find that the most damaging defects are: mismatched voltages between the wire sets and the acceleration voltage of the instrument, which cause positive and negative peaks throughout mass spectra; insufficient deflection voltage, which reduces the intensity of real peaks and causes negative peaks that are spread across the entire mass range; and voltage errors as the wire sets return from their deflection voltage to their transmission value, which yield significant reductions in peak intensities, create artificial peaks throughout mass spectra, and broaden real peaks by causing positive peaks to grow in the bins adjacent to them. Because the magnitude of the modulation defects grows as the applied modulation voltage is increased, Bradbury-Nielson gates with finer wire spacing, and hence stronger effective fields for a given applied voltage, were produced and installed. Operating at 10 to 15 V where errors in the electronics are essentially absent, the most finely spaced gate (100 microm) yielded signal-to-noise ratios that were more than two times higher than those achieved with more widely spaced gates. As an alternative method for minimizing skewing effects, HT-TOFMS data were post processed using an exact knowledge of the modulation defects. Nonbinary matrices that mimic the actual encoding process were built by measuring voltage versus time traces and then translating these traces to transmission versus time. Use of these matrices in the deconvolution step led to marked improvements in spectral resolution but require full knowledge of the encoding defects.

    View details for DOI 10.1016/S1044-0305(03)00006-0

    View details for Web of Science ID 000181561400014

    View details for PubMedID 12648935

  • Flow injection analysis in a microfluidic format ANALYTICAL CHEMISTRY Leach, A. M., Wheeler, A. R., Zare, R. N. 2003; 75 (4): 967-972

    Abstract

    A microfluidic flow injection analysis system has been designed and evaluated. The system incorporates within a single two-layer poly(dimethylsiloxane) monolith multiple pneumatically driven peristaltic pumps, an injection loop, a mixing column, and a transparent window for fluorescence detection. Central to this device is an injection system that mimics the operation of a standard six-port, two-way valve used in conventional liquid chromatography and flow injection experiments. Analyte and carrier solutions continuously flow through this injection system allowing for measurements and sample changes to be performed rapidly and simultaneously. Injection volumes of 1.25 nL generated peak area reproducibility of better than 3% relative standard deviation. The flow injection device was evaluated with fluorescent dyes and demonstrated a detection limit of 400 zmol for fluorescein. A rudimentary sample selection system allowed calibration curves to be rapidly produced, often in less than 10 min. The hydrolysis of fluorescein diphosphate by alkaline phosphatase demonstrates that chemical assays can be carried out with this device in a manner characterized by short analysis times and low sample consumption.

    View details for DOI 10.1021/ac026112l

    View details for Web of Science ID 000181073800038

    View details for PubMedID 12622393

  • Ultratrace kinetic measurements of the reduction of methylene blue JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Hallock, A. J., Berman, E. S., Zare, R. N. 2003; 125 (5): 1158-1159

    Abstract

    The kinetics of methylene blue reduction by ascorbic acid in acetonitrile was investigated by cavity ring-down spectroscopy. Because of our high sensitivity we were able to use very low concentrations (1-10 nM) of the dye. Under these conditions, we observed a second-order loss of dye as well as a competing back reaction with dissolved oxygen. The use of an inexpensive diode laser and a relatively simple setup should make ultratrace kinetic studies more accessible.

    View details for Web of Science ID 000180713000025

    View details for PubMedID 12553804

  • Formation of carbon-carbon bonds in the photochemical alkylation of polycyclic aromatic hydrocarbons ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES Mahajan, T. B., Elsila, J. E., Deamer, D. W., Zare, R. N. 2003; 33 (1): 17-35

    Abstract

    The reaction of polycyclic aromatic hydrocarbons (PAHs) with alkanes was examined in the presence of ultraviolet (UV) light under model prebiotic Earth and interstellar medium (ISM) conditions. We observed the formation of alkylated PAHs from a variety of PAHs and alkanes, which was caused by the absorption of UV light by the PAH molecule. Photoalkylation occurred in PAHs and alkanes in solution, in thin films in contact with simulated ocean water, and in matrices simulating ISM conditions. Photoalkylation occurred readily, with significant product yields within 5 h of irradiation. Because alkanes and PAHs are presumed to be part of the organic inventory in the ISM and on the early Earth, we propose that this photoalkylation reaction is a plausible pathway for the formation of carbon-carbon bonds in both these environments.

    View details for Web of Science ID 000183130500002

    View details for PubMedID 12967271

  • Dynamics of the simplest reaction of a carbon atom in a tetrahedral environment ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Camden, J. P., Bechtel, H. A., Zare, R. N. 2003; 42 (42): 5227-5230

    View details for DOI 10.1022/anie.200352642

    View details for Web of Science ID 000186550800018

    View details for PubMedID 14601179

  • Rotationally resolved photoelectron spectra from vibrationally autoionizing Rydberg states of NO Symposium on Dissociative Recombination of Molecular Ions with Electrons Konen, I., Zhao, R. C., Zare, R. N. KLUWER ACADEMIC/PLENUM PUBL. 2003: 289–299

    View details for Web of Science ID 000188891600028

  • Side group addition to the polycyclic aromatic hydrocarbon coronene by proton irradiation in cosmic ice analogs ASTROPHYSICAL JOURNAL Bernstein, M. P., Moore, M. H., Elsila, J. E., Sandford, S. A., Allamandola, L. J., Zare, R. N. 2003; 582 (1): L25-L29

    View details for Web of Science ID 000180000700005

  • Hadamard transform time-of-flight mass spectrometry: More signal, more of the time ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Zare, R. N., Fernandez, F. M., Kimmel, J. R. 2003; 42 (1): 30-35

    Abstract

    Hadamard transform time-of-flight mass spectrometry (HT-TOF MS) is a type of mass analysis that was developed to couple continuous ion sources to the inherently pulsed nature of time-of-flight measurements. Unlike conventional TOF MS, the Hadamard transform method offers a duty cycle of 50%, with the possibility of extending it to 100%. Because it is a multiplexing technique, the attainable signal-to-noise ratio (SNR) is also significantly higher than that of conventional TOF MS. This review covers the basic principles behind HT-TOF MS. We illustrate, through examples, the source of the high-duty cycle and the increase in SNR. These features translate to a mass spectral storage rate that is the fastest among similar instruments, which enables its use as a detector for high-speed separations.

    View details for Web of Science ID 000180458100006

    View details for PubMedID 19757587

  • Programmable modification of cell adhesion and zeta potential in silica microchips LAB ON A CHIP Kirby, B. J., Wheeler, A. R., Zare, R. N., Fruetel, J. A., Shepodd, T. J. 2003; 3 (1): 5-10

    Abstract

    Spatial patterning of thin polyacrylamide films bonded to self-assembled monolayers on silica microchannels is described as a means for manipulating cell-adhesion and electroosmotic properties in microchips. Streaming potential measurements indicate that the zeta potential is reduced by at least two orders of magnitude at biological pH, and the adhesion of several kinds of cells is reduced by 80-100%. Results are shown for cover slides and in wet-etched silica microchannels. Because the polyacrylamide film is thin and transparent, this film is consistent with optical manipulation of cells and detection of cell contents. The spatial patterning technique is straightforward and has the potential to aid on-chip analysis of single adherent cells.

    View details for DOI 10.1039/b210621n

    View details for Web of Science ID 000181095300004

    View details for PubMedID 15100798

  • Toward sol-gel electrochromatographic separations on a chip JOURNAL OF SEPARATION SCIENCE Morishima, K., Bennett, B. D., Dulay, M. T., Quirino, J. P., Zare, R. N. 2002; 25 (15-17): 1226-1230

    View details for Web of Science ID 000179959200035

  • Visualizing chemistry JOURNAL OF CHEMICAL EDUCATION Zare, R. N. 2002; 79 (11): 1290-1291

    View details for Web of Science ID 000178517000003

  • Functional immobilization of a ligand-activated G-protein-coupled receptor CHEMBIOCHEM Neumann, L., Wohland, T., Whelan, R. J., Zare, R. N., Kobilka, B. K. 2002; 3 (10): 993-998

    Abstract

    G-protein-coupled receptors (GPCRs) mediate the majority of cellular responses to hormones and neurotransmitters. They are the largest family of receptors in the human genome and constitute the largest class of targets for drug discovery. To facilitate studies of GPCR activation and interactions with other proteins, we developed a simple method to immobilize a functional, detergent-solubilized GPCR on gold and glass surfaces. The beta(2) adrenergic receptor (beta(2)AR), a prototypical GPCR, was purified and labeled with a reporter fluorophore at a conformationally sensitive site. The detergent-soluble fluorescent beta(2)AR was immobilized through its amino-terminal FLAG epitope on a surface layered with biotinylated bovine serum albumin, avidin, and biotinylated M1 antibody. Agonist activation of the beta(2)AR was monitored in real time by fluorescence microscopy. This approach will make it possible to study conformational dynamics of single immobilized receptors and to generate arrays of functional GPCRs for novel high-throughput screening strategies.

    View details for Web of Science ID 000178555900009

    View details for PubMedID 12362365

  • Coupled electrorotation of polymer microspheres for microfluidic sensing and mixing ANALYTICAL CHEMISTRY Wilson, C. F., Wallace, M. I., Morishima, K., Simpson, G. J., Zare, R. N. 2002; 74 (19): 5099-5104

    Abstract

    We show that coupled electrorotation (CER) of microscopic particles using microfabricated electrodes can be used for localized sensing and mixing. The effective use of microelectromechanical systems and micro total analysis systems requires many types of control. These include the abilityto (1) manipulate objects within microchannels by noncontact means, (2) mix fluids, and (3) sense local chemical parameters. Coupled electrorotation, in which the interactions between induced electric dipoles of adjacent particles lead to particle rotation, addresses aspects of all three challenges simultaneously. CER is a simple means of controlling the rotation of dielectric objects using homogeneous external radio frequency electric fields. CER is sensitive to several chemical and physical parameters such as the solution conductivity, pH, and viscosity. As a step toward integrating CER devices into microfluidic systems, a simple chip was designed to induce local mixing and to detect local changes in salt concentration, pH, and viscosity.

    View details for DOI 10.1021/ac0258599

    View details for Web of Science ID 000178418100042

    View details for PubMedID 12380836

  • Side group addition to the polycyclic aromatic hydrocarbon coronene by ultraviolet photolysis in cosmic ice analogs ASTROPHYSICAL JOURNAL Bernstein, M. P., Elsila, J. E., Dworkin, J. P., Sandford, S. A., Allamandola, L. J., Zare, R. N. 2002; 576 (2): 1115-1120

    View details for Web of Science ID 000177804800046

  • Capillary electrophoresis separation and native laser-induced fluorescence detection of metallotexaphrins JOURNAL OF SEPARATION SCIENCE Quirino, J. P., Dulay, M. T., Fu, L., Mody, T. D., Zare, R. N. 2002; 25 (13): 819-824

    View details for Web of Science ID 000178547800004

  • Analysis of bimolecular interactions using a miniaturized surface plasmon resonance sensor ANALYTICAL CHEMISTRY Whelan, R. J., Wohland, T., Neumann, L., Huang, B., Kobilka, B. K., Zare, R. N. 2002; 74 (17): 4570-4576

    Abstract

    A commercially available miniaturized surface plasmon resonance sensor has been investigated for its applicability to biological interaction analysis. The sensor was found to exhibit excellent repeatability and linearity for high-refractive index solutions and good reproducibility for the binding of proteins. Its detection limit for the monoclonal antibody M1 was found to be 2.1 fmol, which corresponds to a surface concentration of 21 pg/mm2. Simple surface immobilization procedures relying on biotin/avidin or glycoprotein/lectin chemistry have been explored. Equilibrium dissociation constants for the binding of the FLAG peptide to its monoclonal antibody (M1) and for the binding of concanavalin A to a glycoprotein have been determined. The close agreement of these measurements with values obtained by surface fluorescence microscopy and fluorescence correlation spectroscopy helps to validate the use of this device. Thus, this sensor shows promise as an inexpensive, portable, and accurate tool for bioanalytical applications in laboratory and clinical settings.

    View details for DOI 10.1021/ac025669y

    View details for Web of Science ID 000177862800039

    View details for PubMedID 12236371

  • Temporally resolved cavity ring-down spectroscopy in a pulsed nitrogen plasma APPLIED PHYSICS LETTERS Yalin, A. P., Zare, R. N., Laux, C. O., Kruger, C. H. 2002; 81 (8): 1408-1410

    View details for DOI 10.1063/1.1500427

    View details for Web of Science ID 000177351600014

  • Channel-specific angular distributions of HCl and CH3 products from the reaction of atomic chlorine with stretch-excited methane JOURNAL OF CHEMICAL PHYSICS Kim, Z. H., Bechtel, H. A., Zare, R. N. 2002; 117 (7): 3232-3242

    View details for DOI 10.1063/1.1493192

    View details for Web of Science ID 000177202300028

  • Spatial profiles of N-2(+) concentration in an atmospheric pressure nitrogen flow discharge PLASMA SOURCES SCIENCE & TECHNOLOGY Yalin, A. P., Laux, C. O., Kruger, C. H., Zare, R. N. 2002; 11 (3): 248-253

    View details for Web of Science ID 000178018900004

  • Effect of laser lineshape on the quantitative analysis of cavity ring-down signals LASER PHYSICS Yalin, A. P., Zare, R. N. 2002; 12 (8): 1065-1072

    View details for Web of Science ID 000177820400003

  • Effect of preparatory conditions on the performance of photopolymerized sol-gel monoliths for capillary electrochromatography International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC Kyoto) Kato, M., Sakai-Kato, K., Toyo'oka, T., Dulay, M. T., Quirino, J. P., Bennett, B. D., Zare, R. N. ELSEVIER SCIENCE BV. 2002: 45–51

    Abstract

    We prepared different photopolymerized sol-gel (PSG) columns by varying the amount of monomer (methacryloxypropyltrimethoxysilane), porogen (toluene) and catalyst (hydrochloric acid) in the reaction solution containing a photoinitiator (Irgacure 1800). The effects of these variations on the chromatographic behavior of the PSG columns were studied. All of the columns studied exhibited reversed-phase character. The concentration of hydrochloric acid was important for the rigidity of the columns, although it did not affect the separation property. The ratio of monomer solution to porogen was a critical factor in controlling the through-pore size and the surface area of PSG, which were found to significantly affect the separation properties, such as permeability, theoretical plate number, retention time, and separation efficiency, of a mixture of test analytes-thiourea, benzene, and naphthalene. There was no change in the retention order for the test analytes. Short separation times were achieved on PSG columns made from a 10% monomer stock solution and 90% porogen with 1 M hydrochloric acid. Mixtures of polycyclic aromatic hydrocarbons and alkylbenzenes were separated with theoretical plate numbers greater than 100 000 plates/m.

    View details for Web of Science ID 000177061200006

    View details for PubMedID 12186390

  • Coupled electrorotation: Two proximate microspheres spin in registry with an AC electric field CHEMPHYSCHEM Simpson, G. J., Wilson, C. F., Gericke, K. H., Zare, R. N. 2002; 3 (5): 416-?

    Abstract

    We report a novel approach to micro- and nanoparticle rotation, uniting the fine translational control afforded by optical trapping with the flexibility and simplicity of dipole-field-induced coupled electrorotation (CER). Fluorescence imaging using a microparticle photopatterning technique was combined with optical trapping to quantify both the senses and speeds of rotation for individual pairs of particles. Laser tweezers allowed controlled positioning of a pair of particles within a dipole field while simultaneously providing an axis about which the particles rotated. The particle-particle interactions inherent in CER offer several distinct advantages compared with electrorotation in multipole fields. Results from several investigations highlight the utility of this approach, including quantification of rotation in spheres as small as 750 nm in diameter, observation of rotation rates as high as 1800 rpm, fabrication of coupled electrorotational "antigears", trapping and rotation of sphere dimers, and exploitation of the registry of sphere rotation to probe the dielectric properties of immobile objects.

    View details for Web of Science ID 000175811800005

    View details for PubMedID 12465501

  • Stable isotope ratios using cavity ring-down spectroscopy: Determination of C-13/C-12 for carbon dioxide in human breath ANALYTICAL CHEMISTRY Crosson, E. R., Ricci, K. N., Richman, B. A., Chilese, F. C., Owano, T. G., Provencal, R. A., Todd, M. W., Glasser, J., Kachanov, A. A., Paldus, B. A., Spence, T. G., Zare, R. N. 2002; 74 (9): 2003-2007

    Abstract

    We have constructed a cavity ring-down spectrometer employing a near-IR external cavity diode laser capable of measuring 13C/12C isotopic ratios in CO2 in human breath. The system, which has a demonstrated minimum detectable absorption loss of 3.2 x 10(-11) cm(-1) Hz(-1/2), determines the isotopic ratio of 13C16O16O/12C16O16O by measuring the intensities of rotationally resolved absorption features of each species. As in isotope ratio mass spectrometry (IRMS), the isotopic ratio of a sample is compared to that of a standard CO2 sample calibrated to the Pee Dee Belemnite scale and reported as the sample's delta13C value. Measurements of eight replicate CO2 samples standardized by IRMS and consisting of 5% CO2 in N2 at atmospheric pressure demonstrated a precision of 0.22/1000 for the technique. Delta13C values were also obtained for breath samples from individuals testing positive and negative for the presence of Helicobacter pylori, the leading cause of peptic ulcers in humans. This study demonstrates the ability of the instrument to obtain delta13C values in breath samples with sufficient precision to serve as a useful medical diagnostic.

    View details for DOI 10.1021/ac025511d

    View details for Web of Science ID 000175358800036

    View details for PubMedID 12033299

  • State-resolved differential and integral cross sections for the reaction H+D-2 -> HD(v '=3,j(')=0-7)+D at 1.64 eV collision energy JOURNAL OF CHEMICAL PHYSICS Bean, B. D., Ayers, J. D., Fernandez-Alonso, F., Zare, R. N. 2002; 116 (15): 6634-6639

    View details for DOI 10.1063/1.1462576

    View details for Web of Science ID 000174767200027

  • Hadamard transform time-of-flight mass spectrometry: A high-speed detector for capillary-format separations ANALYTICAL CHEMISTRY Fernandez, F. M., Vadillo, J. M., Kimmel, J. R., Wetterhall, M., Markides, K., Rodriguez, N., Zare, R. N. 2002; 74 (7): 1611-1617

    Abstract

    This work demonstrates that with an intrinsic duty cycle of 50% and spectral storage speeds up to 277 spectra s(-1) Hadamard transform time-of-flight mass spectrometry (HT-TOFMS) is a promising detector for any capillary-format separation that can be coupled to MS by electrospray ionization. Complete resolution of the components of a nine-peptide standard was achieved by coupling pressurized-capillary electrophoresis (pCE) to HT-TOFMS. The addition of pressure to the separation capillary decreased analysis times and stabilized the electrospray ionization source. Pulsed-pressurized injection of reserpine was used to experimentally simulate narrower peaks than those obtained in the pCE. HT-TOFMS was able to sample peaks having widths in the millisecond range.

    View details for DOI 10.1021/ac015673u

    View details for Web of Science ID 000174841600031

    View details for PubMedID 12033252

  • Direct monitoring of absorption in solution by cavity ring-down spectroscopy ANALYTICAL CHEMISTRY Hallock, A. J., Berman, E. S., Zare, R. N. 2002; 74 (7): 1741-1743

    Abstract

    Cavity ring-down spectroscopy is applied to the liquid phase by placing the target solution directly into the optical cavity. We demonstrate that solutions in the cavity can be stirred and more importantly monitored in a flow. We report a minimum detectable absorption of 10(-6) cm(-1) for a range of organic solvents. This detection limit corresponds to picomolar concentrations for strong absorbers.

    View details for DOI 10.1021/ac011103i

    View details for Web of Science ID 000174841600050

    View details for PubMedID 12033270

  • Observation and interpretation of a time-delayed mechanism in the hydrogen exchange reaction NATURE Althorpe, S. C., Fernandez-Alonso, F., Bean, B. D., Ayers, J. D., Pomerantz, A. E., Zare, R. N., Wrede, E. 2002; 416 (6876): 67-70

    Abstract

    Extensive theoretical and experimental studies have shown the hydrogen exchange reaction H+H2 --> H2+H to occur predominantly through a 'direct recoil' mechanism: the H--H bonds break and form concertedly while the system passes straight over a collinear transition state, with recoil from the collision causing the H2 product molecules to scatter backward. Theoretical predictions agree well with experimental observations of this scattering process. Indirect exchange mechanisms involving H3 intermediates have been suggested to occur as well, but these are difficult to test because bimolecular reactions cannot be studied by the femtosecond spectroscopies used to monitor unimolecular reactions. Moreover, full quantum simulations of the time evolution of bimolecular reactions have not been performed. For the isotopic variant of the hydrogen exchange reaction, H+D2 --> HD+D, forward scattering features observed in the product angular distribution have been attributed to possible scattering resonances associated with a quasibound collision complex. Here we extend these measurements to a wide range of collision energies and interpret the results using a full time-dependent quantum simulation of the reaction, thus showing that two different reaction mechanisms modulate the measured product angular distribution features. One of the mechanisms is direct and leads to backward scattering, the other is indirect and leads to forward scattering after a delay of about 25 femtoseconds.

    View details for Web of Science ID 000174211600038

    View details for PubMedID 11882892

  • Irradiation of dye-doped microspheres with a stronqly focused laser beam results in alignment upon optical trapping NANO LETTERS Sirnpson, G. J., Wohland, T., Zare, R. N. 2002; 2 (3): 207-210

    View details for DOI 10.1021/nl015632d

    View details for Web of Science ID 000174640900008

  • Electroosmotic flow pumps with polymer frits SENSORS AND ACTUATORS B-CHEMICAL Zeng, S. L., Chen, C. H., Santiago, J. G., Chen, J. R., Zare, R. N., Tripp, J. A., Svec, F., Frechet, J. M. 2002; 82 (2-3): 209-212

    View details for Web of Science ID 000174483000010

  • Genetic screening using the colour change of a PNA-DNA hybrid-binding cyanine dye NUCLEIC ACIDS RESEARCH Wilhelmsson, L. M., Norden, B., Mukherjee, K., Dulay, M. T., Zare, R. N. 2002; 30 (2)

    Abstract

    As the relationship between human genes and various malfunctions and diseases becomes revealed at an ever-increasing pace, the need arises for the development of rapid genetic screening methods for diagnostic purposes. Genetic diseases show great diversity. Some are caused by a few characteristic localised mutations, while others arise from a large number of variations. Hence, it is unlikely that a single, general diagnostic method that applies to all cases will ever exist. Instead, a combination of methods is frequently applied. Here we propose the use of a dramatic colour change that a cyanine dye, 3,3'-diethylthiadicarbocyanine, displays upon binding to DNA-PNA duplexes. This method could become an inexpensive, fast and simple genetic screening test by visual inspection, with no need for complicated equipment. Our results demonstrate that this diagnostic method may be sufficiently sensitive to discriminate between even a fully complementary and a single mutation DNA sequence.

    View details for Web of Science ID 000173551200027

    View details for PubMedID 11788729

  • Scattering resonances in the simplest chemical reaction ANNUAL REVIEW OF PHYSICAL CHEMISTRY Fernandez-Alonso, F., Zare, R. N. 2002; 53: 67-99

    Abstract

    Recent studies of state-resolved angular distributions show the participation of reactive scattering resonances in the simplest chemical reaction. This review is intended for those who wish to learn about the state-of-the-art in the study of the H + H2 reaction family that has made this breakthrough possible. This review is also intended for those who wish to gain insight into the nature of reactive scattering resonances. Following a tour across several fields of physics and chemistry where the concept of resonance has been crucial for the understanding of new phenomena, we offer an operational definition and taxonomy of reactive scattering resonances. We introduce simple intuitive models to illustrate each resonance type. We focus next on the last decade of H + H2 reaction dynamics. Emphasis is placed on the various experimental approaches that have been applied to the search for resonance behavior in the H + H2 reaction family. We conclude by sketching the road ahead in the study of H + H2 reactive scattering resonances.

    View details for DOI 10.1146/annurev.physchem.53.091001.194554

    View details for Web of Science ID 000176264900005

    View details for PubMedID 11972003

  • Bonded-phase photopolymerized sol-gel monoliths for reversed phase capillary electrochromatography JOURNAL OF SEPARATION SCIENCE Dulay, M. T., Quirino, J. P., Bennett, B. D., Zare, R. N. 2002; 25 (1-2): 3-9

    View details for Web of Science ID 000173610600002

  • Analysis of Biomolecular Interactions Using a Miniaturized Plasmon Resonance Sensor Anal. Chem. Whelan, R. J., Wohland, T., Neumann, L., Huang, B., Kobilka, B. K., Zare, R. N. 2002; 74: 4570-4576
  • Observation of Scattering Resonances in the H+D2 Reaction: Direct Probe of the HD2 Transition-State Geometry Femtochemistry And Femtobiology: Ultrafast Dynamics in Molecular Science Aoiz, F. J., Bañares, L., Castillo, J. F., Sokolovski, D., Alonso, F. F., Bean, B. D., Ayers, J. D., Pomerantz, A. E., Zare, R. N. World Scientific Press. 2002: 61–72
  • Electroosmotic Flow Pumps with Large Flow Rates Sensors & Actuators B Zeng, S., Chen, C. H., Santiago, J. G., Chen, J. R., Zare, R. N., Tripp, J. A., Svec, F., Frechet, J. J. 2002; 82: 209-212
  • Irradiation of Dye-Doped Microspheres with a Strongly Focused Laser Beam Results in Alignment upon Optical Trapping Nano Letters Simpson, G. J., Wohland, T., Zare, R. N. 2002; 2 (3): 207-210
  • Formation of Carbon-Carbon bonds in Photochemical Alkylation of Polycyclic Aromatic Hydrocarbons The Origins and Early Evolution of Life Mahajan, T. B., Elsila, J. E., Deamer, D. W., Zare, R. N. 2002; 139
  • Microscale detection of polychlorinated biphenyls using two-step laser mass spectrometry INTERNATIONAL JOURNAL OF MASS SPECTROMETRY Mahajan, T. B., Ghosh, U., Zare, R. N., Luthy, R. G. 2001; 212 (1-3): 41-48

    View details for Web of Science ID 000173003600007

  • Vibrational control in the reaction of methane with atomic chlorine JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Kim, Z. H., Bechtel, H. A., Zare, R. N. 2001; 123 (50): 12714-12715

    View details for DOI 10.1021/ja017180c

    View details for Web of Science ID 000172745300046

    View details for PubMedID 11741451

  • Novel method for the production of finely spaced Bradbury-Nielson gates REVIEW OF SCIENTIFIC INSTRUMENTS Kimmel, J. R., Engelke, F., Zare, R. N. 2001; 72 (12): 4354-4357

    View details for Web of Science ID 000172387400005

  • Effect of sequence length, sequence frequency, and data acquisition rate on the performance of a Hadamard transform time-of-flight mass spectrometer JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Fernandez, F. M., Vadillo, J. M., Engelke, F., Kimmel, J. R., Zare, R. N., Rodriguez, N., Wetterhall, M., Markides, K. 2001; 12 (12): 1302-1311

    Abstract

    Various factors influencing the performance of a Hadamard transform time-of-flight mass spectrometer (HT-TOFMS) have been investigated. Using a nitrogen corona discharge to produce an ion stream of N2+, N3+, and N4+, it is found for spectra containing only N4+ that the signal-to-noise ratio (SNR) closely approaches the value calculated from the ion background by assuming that the ion background follows a Poisson distribution. In contrast, for a more intense beam containing N2+, N3+, and N4+, the SNR is less than its theoretical value because of the appearance of discrete spikes in the mass spectrum caused by deviations in the actual modulation sequence from the ideal one. These spikes can be reduced, however, by decreasing the modulation voltage. Under these optimized conditions, the pseudo-random sequence length is varied to understand how it alters SNR, mass resolution, and scan speed. When the length of the pseudo-random sequence is doubled, the SNR increases by the square root of 2 while the time necessary to record a mass spectrum also doubles. Mass resolution can be varied between 500 and 1200 at m/z = 609 as the sequence length, modulation speed (10 MHz, 25 MHz), and acquisition rate (up to 50 MHz) are changed. Scan speeds of 6000 passes per s can be obtained using a sequence containing 4095 elements modulated at 25 MHz. The capability to tailor the HT-TOFMS to increase the scan speed and resolution with a constant 50% duty cycle makes the technique extremely appealing as a mass analyzer for measuring rapid changes in the composition of an ion stream.

    View details for Web of Science ID 000172644400009

    View details for PubMedID 11766757

  • Strategy for on-line preconcentration in chromatographic separations ANALYTICAL CHEMISTRY Quirino, J. P., Dulay, M. T., Bennett, B. D., Zare, R. N. 2001; 73 (22): 5539-5543

    Abstract

    In chromatographic separations, the heights of peaks are proportional to the concentrations of sample components present in an injected mixture. In general, an increase in the peak height cannot be achieved by simply increasing the injection time or the sample plug length. An exception occurs if some form of on-line preconcentration is possible. We present a new strategy for achieving on-line preconcentration by the use of a porous chromatographic material that acts as a solid-phase extractor as well as a stationary-phase separator. We are able to realize significant on-line preconcentration using capillary columns filled with a photopolymerized sol-gel (PSG). More than 2-cm plugs of sample solution can be loaded into the capillary and concentrated using a running buffer that is the same as the injection buffer (to avoid solvent gradient effects). As a demonstration, mixtures of three different polycyclic aromatic hydrocarbons, eight different alkyl phenyl ketones, and five different peptides in solutions of aqueous acetonitrile have been injected onto the PSG column and separated by capillary electrochromatography. The preconcentration is marked in terms of peak heights, with up to 100-fold increase for the PAH mixture, 30-fold for the alkyl phenyl ketone mixture, and 20-fold for the peptide mixture. Preconcentration takes place because of the high mass-transfer rates possible in the highly porous structure, and the extent of preconcentration follows the retention factor k for a given analyte.

    View details for DOI 10.1021/ac015522r

    View details for Web of Science ID 000172209400027

    View details for PubMedID 11816585

  • On-line preconcentration in capillary electrochromatography using a porous monolith together with solvent gradient and sample stacking ANALYTICAL CHEMISTRY Quirino, J. P., Dulay, M. T., Zare, R. N. 2001; 73 (22): 5557-5563

    Abstract

    Preconcentration effects of solvent gradient and sample stacking are investigated on a photopolymerized sol-gel (PSG) in capillary electrochromatography. The porous PSG monolith has a high mass-transfer rate. This characteristic promotes preconcentration of dilute samples. Plugs of samples more than 2 cm in length prepared in the separation solution (nongradient condition) are injected onto the PSG column. The extent of preconcentration is quite significant, showing up to a 100-fold increase in peak heights of the separated analytes. Even larger preconcentrations are achieved under gradient conditions by dissolving the sample in a matrix with a higher concentration of noneluting solvent (water). For eight alkyl phenyl ketones and four polycyclic aromatic hydrocarbons that serve as neutral test analytes, improvements in peak heights obtained under gradient conditions can be more than a 1000-fold. Indeed, injection of a 91.2-cm plug, which is more than 3 times the total length of the capillary, was possible with only a minor loss in resolution. Five peptides serve as charged test analytes. Nongradient conditions in which the sample is hydrodynamically injected onto the PSG column show sizable preconcentration because of sample stacking. The use of a solvent gradient with the same ionic strength, however, does not appear to have practical value because of destacking caused by the changing organic composition that affects the conductivity. As an alternative preconcentration method, we demonstrate that electric field-enhanced sample injection on the PSG yielded up to a 1000-fold improvement in detection sensitivity for the test peptides.

    View details for Web of Science ID 000172209400030

    View details for PubMedID 11816588

  • N-2 product internal-state distributions for the steady-state reactions of NO with H-2 and NH3 on the Pt(100) surface JOURNAL OF PHYSICAL CHEMISTRY B Hallock, A. J., Matthews, C. M., Balzer, F., Zare, R. N. 2001; 105 (37): 8725-8728

    View details for Web of Science ID 000171032600012

  • Forward scattering in the H+D-2 -> HD+D reaction: Comparison between experiment and theoretical predictions JOURNAL OF CHEMICAL PHYSICS Fernandez-Alonso, F., Bean, B. D., Zare, R. N., Aoiz, F. J., Banares, L., Castillo, J. F. 2001; 115 (10): 4534-4545

    View details for Web of Science ID 000170647600015

  • Comparison of microprobe two-step laser desorption/laser ionization mass spectrometry and gas chromatography/mass spectrometry studies of polycyclic aromatic hydrocarbons in ancient terrestrial rocks JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY Mahajan, T. B., Plows, F. L., Gillette, J. S., Zare, R. N., Logan, G. A. 2001; 12 (9): 989-1001

    View details for Web of Science ID 000171108600002

  • Photopolymerized sol-gel monoliths for capillary electrochromatography ANALYTICAL CHEMISTRY Dulay, M. T., Quirino, J. P., Bennett, B. D., Kato, M., Zare, R. N. 2001; 73 (16): 3921-3926

    Abstract

    A solution of methacryloxypropyltrimethoxysilane in the presence of an acid catalyst, water, toluene, and a photoinitiator was irradiated at 365 nm for 5 min in a 75-microm i.d. capillary to prepare a porous monolithic sol-gel column by a one-step, in situ, process. The photopolymerized sol-gel (PSG) column shows reversed-phase behavior. Using this column, a variety of low-molecular-weight neutral compounds, including polycyclic aromatic hydrocarbons, alkyl benzenes, alkyl phenyl ketones, and steroids are separated from mixtures. Various different operational parameters, such as buffer composition, field strength, and column temperature, were varied to assess their influence on column performance. Use of PSG as a stationary phase for a pressure-driven separation is also demonstrated.

    View details for DOI 10.1006/ac0100749

    View details for Web of Science ID 000170482800019

    View details for PubMedID 11534717

  • Photopolymerized sol-gel frits for packed columns in capillary electrochromatography 14th International Symposium on Microscale Separations and Analysis Kato, M., Dulay, M. T., Bennett, B. D., Quirino, J. P., Zare, R. N. ELSEVIER SCIENCE BV. 2001: 187–95

    Abstract

    Porous sol-gel frits are fabricated in a capillary column by filling it with a solution of 3-(trimethoxysilyl)propyl methacrylate, hydrochloric acid, water, toluene (porogen), and a photoinitiator (Irgacure 1800) and exposing it to UV light at 365 nm for 5 min. The separation column (30 cm x 75 microm I.D.) contains between the inlet and outlet frits a 15-cm packed segment filled with 5-microm silica particles modified with the chiral compound (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine. A detection window (1 mm long) is placed immediately after the outlet frit. To demonstrate the performance of this chiral separation column, mixtures of 16 different amino acids (three of which are not naturally occurring) derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole were separated by capillary chromatography. The enantiomeric separation of the column results in a resolution ranging from 1.21 to 8.29, and a plate height ranging from 8.7 to 39 microm.

    View details for Web of Science ID 000170359200018

    View details for PubMedID 11521865

  • Electrophoretron: a new method for enhancing resolution in electrokinetic separations 14th International Symposium on Microscale Separations and Analysis Choi, J. G., Kim, M., Dadoo, R., Zare, R. N. ELSEVIER SCIENCE BV. 2001: 53–58

    Abstract

    Two capillaries, each of which have different surface preparations on their inside walls, are joined together to form a closed loop, and electrodes are placed inside the two capillaries. When the loop is filled with liquid and a potential difference is applied between the two electrodes, a circulating flow of liquid is established inside the loop because the resistance to flow is unequal in going from one electrode to another in a clockwise versus a counterclockwise direction. Consequently, a sample injected into this device, which we call an electrophoretron, repeatedly circulates between the two electrodes and the capillary separation column becomes effectively one of unlimited length. On each cycle the separation between analytes with different mobilities increases, thus enhancing resolution of analytes having nearly the same mobilities. The operation of a prototype electrophoretron is demonstrated.

    View details for Web of Science ID 000170359200005

    View details for PubMedID 11521906

  • Single-molecule spectroscopy of the beta(2) adrenergic receptor: Observation of conformational substates in a membrane protein PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Peleg, G., Ghanouni, P., Kobilka, B. K., Zare, R. N. 2001; 98 (15): 8469-8474

    Abstract

    Single-molecule studies of the conformations of the intact beta(2) adrenergic receptor were performed in solution. Photon bursts from the fluorescently tagged adrenergic receptor in a micelle were recorded. A photon-burst algorithm and a Poisson time filter were implemented to characterize single molecules diffusing across the probe volume of a confocal microscope. The effects of molecular diffusion and photon number fluctuations were deconvoluted by assuming that Poisson distributions characterize the molecular occupation and photon numbers. Photon-burst size histograms were constructed, from which the source intensity distributions were extracted. Different conformations of the beta(2) adrenergic receptor cause quenching of the bound fluorophore to different extents and hence produce different photon-burst sizes. An analysis of the photon-burst histograms shows that there are at least two distinct substates for the native adrenergic membrane receptor. This behavior is in contrast to one peak observed for the dye molecule, rhodamine 6G. We test the reliability and robustness of the substate number determination by investigating the application of different binning criteria. Conformational changes associated with agonist binding result in a marked change in the distribution of photon-burst sizes. These studies provide insight into the conformational heterogeneity of G protein-coupled receptors in the presence and absence of a bound agonist.

    View details for Web of Science ID 000169967000049

    View details for PubMedID 11438704

    View details for PubMedCentralID PMC37459

  • Vibrational and collisional energy effects in the reaction of ammonia ions with methylamine JOURNAL OF CHEMICAL PHYSICS Flad, J. E., Everest, M. A., Poutsma, J. C., Zare, R. N. 2001; 115 (1): 124-132

    View details for Web of Science ID 000169385300014

  • Comparison of near-threshold reactivity of ground-state and spin-orbit excited chlorine atoms with methane JOURNAL OF CHEMICAL PHYSICS Kim, Z. H., Alexander, A. J., Bechtel, H. A., Zare, R. N. 2001; 115 (1): 179-183

    View details for Web of Science ID 000169385300021

  • Cavity ring-down spectroscopy of CH and CD radicals in a diamond thin film chemical vapor deposition reactor APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Lommatzsch, U., Wahl, E. H., Aderhold, D., Owano, T. G., Kruger, C. H., Zare, R. N. 2001; 73 (1): 27-33

    View details for Web of Science ID 000169584100003

  • Semipreparative capillary electrochromatography ANALYTICAL CHEMISTRY Chen, J. R., Zare, R. N., Peters, E. C., Svec, F., Frechet, J. J. 2001; 73 (9): 1987-1992

    Abstract

    Capillaries with inner diameters of 550 microm have successfully been packed with 1.5-microm octadecyl silica particles using frits made of macroporous polymers by the UV photopolymerization of a solution of glycidyl methacrylate and trimethylolpropane trimethacrylate. This type of frit is found superior to one made of low-melting point poly(styrene-co-divinylbenzene) beads. Bubble formation is not observed to occur within these capillary columns under our experimental conditions. Separations can be achieved with sample injection volumes as high as 1 microL. To demonstrate its semipreparative use, a mixture of 500 nL of taxol (20 mM) and its precursor, baccatin III (30 mM), is separated using such a column with a Tris buffer.

    View details for Web of Science ID 000168519800017

    View details for PubMedID 11354480

  • Low temperature ice photochemistry as a source of meteoritic and cometary organics. Elsila, J. E., Gillette, J. S., Zare, R. N., Bernstein, M. P., Dworkin, J. P., Sandford, S. A., Allamandola, L. J. AMER CHEMICAL SOC. 2001: U540–U540

    View details for Web of Science ID 000168824703564

  • Distribution of rovibrational product states for the "prompt" reaction H+D-2(nu=0,j=0-4) -> HD(nu '=1,2,j ')+D near 1.6 eV collision energy JOURNAL OF PHYSICAL CHEMISTRY A Bean, B. D., Fernandez-Alonso, F., Zare, R. N. 2001; 105 (11): 2228-2233

    View details for DOI 10.1021/jp0027288

    View details for Web of Science ID 000167632400013

  • Bounce-by-bounce cavity ring-down spectroscopy: Femtosecond temporal imaging CHEMPHYSCHEM Shaw, A. M., Zare, R. N., Bennett, C. V., Kolner, B. H. 2001; 2 (2): 118-?

    Abstract

    A time microscope (100× magnification) allows light pulses exiting an optical cavity to be viewed one at a time. A linearly chirped Gaussian pulse is mixed in a nonlinear crystal with the dispersed input waveform; the up-converted light is sent onto an output dispersive network. The resulting temporal image is recorded both with a streak camera and with a spectrometer.

    View details for Web of Science ID 000168286600005

    View details for PubMedID 23696438

  • Nanoengineered structures for holding and manipulating liposomes and cells ANALYTICAL CHEMISTRY Wilson, C. F., Simpson, G. J., Chiu, D. T., Stromberg, A., Orwar, O., Rodriguez, N., Zare, R. N. 2001; 73 (4): 787-791

    Abstract

    We describe the fabrication of nanoengineered holding pipets with concave seating surfaces and fine pressure control. These pipets were shown to exhibit exceptional stability in capturing, transporting, and releasing single cells and liposomes 1-12 microm in diameter, which opens previously inaccessible avenues of research. Three specific examples demonstrated the utility and versatility of this manipulation system. In the first, carboxyrhodamine was selectively incorporated into individual cells by electroporation, after which nearly all the medium (hundreds of microliters) surrounding the docked and tagged cells was rapidly exchanged (in seconds) and the cells were subsequently probed by laser-induced fluorescence (LIF). In the second study, a single liposome containing carboxyrhodamine was transported to a dye-free solution using a transfer pipet, docked to a holding pipet, and held firmly during physical agitation and interrogation by LIF. In the third study, pairs of liposomes were positioned between two microelectrodes, held in contact, and selectively electrofused and the resulting liposomes undocked intact.

    View details for DOI 10.1021/ac001020m

    View details for Web of Science ID 000167076700010

    View details for PubMedID 11248893

  • Microprobe laser mass spectrometry studies of polycyclic aromatic hydrocarbon distributions on harbor sediments and coals ISRAEL JOURNAL OF CHEMISTRY Gillette, J. S., Ghosh, U., Mahajan, T. B., Zare, R. N., Luthy, R. G. 2001; 41 (2): 105-110

    View details for Web of Science ID 000172703700005

  • On the One Hand But Not the Other: The Challenge of the Origin and Survival of Homochirality in Prebiotic Chemistry Chemistry for the 21st Century Frank, P., Bonner, W. A., Zare, R. N. edited by Keinan, E., Schechter, I. Wiley-VCH Gmbh: Weinheim, Germany. 2001: 175–208
  • Confining and Probing Single Molecules in Synthetic Liposomes Single-Molecule Spectroscopy: Nobel Conference Lectures Wilson, C. F., Chiu, D. T., Zare, R. N., Stromberg, A., Karlsson, A., Orwar, O. edited by Rigler, R., Orrit, M., Basche, T. Springer-Verlag: Berlin Heidelberg. 2001
  • Nanoforms: A new type of protein-associated mineralization GEOCHIMICA ET COSMOCHIMICA ACTA Vali, H., McKee, M. D., Ciftcioglu, N., Sears, S. K., Plows, F. L., Chevet, E., Ghiabi, P., Plavsic, M., Kajander, E. O., Zare, R. N. 2001; 65 (1): 63-74

    View details for Web of Science ID 000166362200006

  • Oriented chlorine atoms as a probe of the nonadiabatic photodissociation dynamics of molecular chlorine JOURNAL OF CHEMICAL PHYSICS Alexander, A. J., Kim, Z. H., Kandel, S. A., Zare, R. N., Rakitzis, T. P., Asano, Y., Yabushita, S. 2000; 113 (20): 9022-9031

    View details for Web of Science ID 000165217000018

  • Mode selectivity in ion-molecule reactions of NH3+ APPLIED PHYSICS B-LASERS AND OPTICS Poutsma, J. C., Everest, M. A., Flad, J. E., Zare, R. N. 2000; 71 (5): 623-625

    View details for Web of Science ID 000165410800003

  • Remarks on the signs of g factors in atomic and molecular Zeeman spectroscopy MOLECULAR PHYSICS Brown, J. M., Buenker, R. J., Carrington, A., di Lauro, C., Dixon, R. N., Field, R. W., Hougen, J. T., Huttner, W., KUCHITSU, K., Mehring, M., Merer, A. J., Miller, T. A., QUACK, M., Ramsay, D. A., Veseth, L., Zare, R. N. 2000; 98 (20): 1597-1601

    View details for Web of Science ID 000089819200001

  • Chemical physics - Spinning molecules to bits NATURE Gupta, M., Zare, R. N. 2000; 407 (6800): 33-34

    View details for Web of Science ID 000089124000027

  • Enantiomeric separation of amino acids and nonprotein amino acids using a particle-loaded monolithic column ELECTROPHORESIS Kato, M., Dulay, M. T., Bennett, B., Chen, J. R., Zare, R. N. 2000; 21 (15): 3145-3151

    Abstract

    A solution is prepared of 5 microm silica particles modified with (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine (particle 1) or (S)-N-3,5-dinitrophenylaminocarbonyl-valine (particle 2) suspended in liquid tetraethylorthosilicate, ethanol, and aqueous hydrochloric acid. This solution is injected under pressure into a 30 cm long, 75 microm inner diameter capillary column and heated for 1 h at 120 degrees C after which the modified particles are embedded in a monolithic column of sol gel. The packed column measures approximately 15 cm from the inlet to the window used to view the laser-induced fluorescence. Thirteen different amino acids and three nonprotein amino acids are derivatized with the fluorogenic reagent 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) before injection onto the column for capillary electrochromatographic separation. The enantiomeric separation of the monolithic column packed with particle 1 results in a resolution ranging from 1.14 to 4.45, whereas that packed with particle 2 results in a resolution ranging from 0.79 to 1.17. On the basis of resolution and amount of chiral packing material the enantiomeric separation obtained by capillary electrochromatography is judged to be superior to that obtained previously with high performance liquid chromatography (HPLC).

    View details for Web of Science ID 000089318300012

    View details for PubMedID 11001212

  • Interstellar ice photochemistry and the deuterium enrichment and chemical properties of meteoritic polycyclic aromatic hydrocarbons. Sandford, S. A., Bernstein, M. P., Allamandola, L. J., Gillette, J. S., Zare, R. N. WILEY-BLACKWELL. 2000: A141–A141

    View details for Web of Science ID 000089787400246

  • Evidence for Scattering Resonances in the H+D(2) Reaction We thank Donald G. Truhlar, Patrick Brown, Zee Hwan Kim, and Stephen Cho for careful and critical reading of the manuscript prior to publication. We also thank Andrew J. Alexander for his assistance in the preparation of the polar plots. Elf-Atochem (B.D.B.), the Hertz Foundation and Stanford University (J.D.A.), and the National Science Foundation (A.E.P.) are gratefully acknowledged for their support in the form of Graduate Fellowships. This work was supported at Stanford University by the U.S. National Science Foundation under Grant Number CHE-99-00305 and at Universidad Complutense by DGCYT PB98-0762-C03-01. Angewandte Chemie (International ed. in English) Fernández-Alonso, BEAN, Ayers, Pomerantz, Zare, Bañares, Aoiz 2000; 39 (15): 2748-2752

    View details for PubMedID 10934414

  • Deuterium enrichment of polycyclic aromatic hydrocarbons by photochemically induced exchange with deuterium-rich cosmic ices ASTROPHYSICAL JOURNAL Sandford, S. A., Bernstein, M. P., Allamandola, L. J., Gillette, J. S., Zare, R. N. 2000; 538 (2): 691-697

    Abstract

    The polycyclic aromatic hydrocarbon (PAH) coronene (C24H12) frozen in D2O ice in a ratio of less than 1 part in 500 rapidly exchanges its hydrogen atoms with the deuterium in the ice at interstellar temperatures and pressures when exposed to ultraviolet radiation. Exchange occurs via three different chemical processes: D atom addition, D atom exchange at oxidized edge sites, and D atom exchange at aromatic edge sites. Observed exchange rates for coronene (C24H12)-D2O and d12-coronene (C24D12)-H2O isotopic substitution experiments show that PAHs in interstellar ices could easily attain the D/H levels observed in meteorites. These results may have important consequences for the abundance of deuterium observed in aromatic materials in the interstellar medium and in meteorites. These exchange mechanisms produce deuteration in characteristic molecular locations on the PAHs that may distinguish them from previously postulated processes for D enrichment of PAHs.

    View details for Web of Science ID 000088824800024

    View details for PubMedID 11543580

  • Scattering of N-2 from Ni(111) SURFACE SCIENCE Matthews, C. M., Balzer, F., Hallock, A. J., Ellison, M. D., Zare, R. N. 2000; 460 (1-3): 12-20

    View details for Web of Science ID 000088689700004

  • Frequency-switched heterodyne cavity ringdown spectroscopy OPTICS LETTERS Levenson, M. D., Paldus, B. A., Spence, T. G., Harb, C. C., Zare, R. N., Lawrence, M. J., Byer, R. L. 2000; 25 (12): 920-922

    Abstract

    When the frequency of light coupled into a cavity is suddenly shifted, the radiation emanating from the input port of the previously excited cavity can beat with the reflection of the frequency-shifted input on the surface of a photodetector. When the beat frequency is stable, the time decay of the resulting optical heterodyne signal can be used to measure intracavity absorption spectra with near quantum-limited sensitivity.

    View details for Web of Science ID 000087642400018

    View details for PubMedID 18064227

  • Microscale location, characterization, and association of polycyclic aromatic hydrocarbons on harbor sediment particles ENVIRONMENTAL SCIENCE & TECHNOLOGY Ghosh, U., Gillette, J. S., Luthy, R. G., Zare, R. N. 2000; 34 (9): 1729-1736

    View details for Web of Science ID 000086794500033

  • Cavity ringdown spectroscopy using mid-infrared quantum-cascade lasers OPTICS LETTERS Paldus, B. A., Harb, C. C., Spence, T. G., Zare, R. N., Gmachl, C., Capasso, F., Sivco, D. L., Baillargeon, J. N., Hutchinson, A. L., Cho, A. Y. 2000; 25 (9): 666-668

    Abstract

    Cavity ringdown spectra of ammonia at 10 parts in 10(9) by volume (ppbv) and higher concentrations were recorded by use of a 16-mW continuous-wave quantum-casacde distributed-feedback laser at 8.5 mum whose wavelength was continuously temperature tuned over 15 nm. A sensitivity (noise-equivalent absorbance) of 3.4x10(-9) cm(-1) Hz(-1/2) was achieved for ammonia in nitrogen at standard temperature and pressure, which corresponds to a detection limit of 0.25 ppbv.

    View details for Web of Science ID 000086680100025

    View details for PubMedID 18064145

  • Partial-wave decomposition of the ionization continuum accessed by vibrational autoionization of the NO 14s (nu=1, N=20, N-R(+)=20) level PHYSICAL REVIEW LETTERS Park, H., Konen, I., Zare, R. N. 2000; 84 (17): 3819-3822

    View details for Web of Science ID 000086635900022

  • Spatial concentration and temperature distribution of CH radicals formed in a diamond thin-film hot-filament reactor CHEMICAL PHYSICS LETTERS Lommatzsch, U., Wahl, E. H., Owano, T. G., Kruger, C. H., Zare, R. N. 2000; 320 (3-4): 339-344

    View details for Web of Science ID 000086308400021

  • Molecular tennis - Flat smashes and wicked cuts ACCOUNTS OF CHEMICAL RESEARCH Alexander, A. J., Zare, R. N. 2000; 33 (4): 199-205

    Abstract

    Molecular photodissociation typically produces open-shell photofragments that have angular momentum. This Account explores how the measurement of the directional nature of photofragment angular momentum can provide us with a new viewpoint for seeing and understanding the process whereby molecules fall apart under irradiation. Although the photodissociation process is more complicated than might be imagined at first, the measurements reveal detail that approaches conventional bound-state spectroscopy, enhancing our understanding of the chemical bond and even allowing us to manipulate the ultimate fate of a photofragment by selecting the wavelength and the polarization of the photolysis source.

    View details for Web of Science ID 000086787200001

    View details for PubMedID 10775312

  • Softening of fused-silica capillaries during particle packing ELECTROPHORESIS Chen, J. R., Dulay, M. T., Zare, R. N. 2000; 21 (7): 1430-1431

    Abstract

    When a semipreparative capillary electrochromatography (CEC) capillary is packed with silica particles and exposed to solvent, its mechanical strength is markedly reduced. In our studies, a fused-silica capillary (internal diameter > 200 microm and wall thickness < 150 microm) was packed under pressure (approximately 200 psi) with spherical silica particles (1.5-5 microm) suspended in water or various common organic solvents. After one hour of exposure, the capillary can be readily deformed, and it keeps its deformed shape upon release of the force causing deformation. It is suggested that capillary softening is promoted through the propagation of internal microcracks that have been caused by action of the particles during packing in the presence of solvent. Application of a protective coating to the inside of the capillary is found to reduce or eliminate capillary softening.

    View details for Web of Science ID 000087022300025

    View details for PubMedID 10826691

  • Macroporous photopolymer frits for capillary electrochromatography ANALYTICAL CHEMISTRY Chen, J. R., Dulay, M. T., Zare, R. N., Svec, F., Peters, E. 2000; 72 (6): 1224-1227

    View details for Web of Science ID 000085975200018

  • Near-surface reduction of cavity ring-down spectroscopy detection sensitivity CHEMICAL PHYSICS LETTERS Zhao, M. S., Wahl, E. H., Owano, T. G., Largent, C. C., Zare, R. N., Kruger, C. H. 2000; 318 (6): 555-560

    View details for Web of Science ID 000085722600010

  • Characterization of a Hadamard transform time-of-flight mass spectrometer REVIEW OF SCIENTIFIC INSTRUMENTS Brock, A., Rodriguez, N., Zare, R. N. 2000; 71 (3): 1306-1318

    View details for Web of Science ID 000085688600009

  • Ultraviolet photoprocessing of interstellar dust mantles as a source of polycyclic aromatic hydrocarbons and other conjugated molecules ASTROPHYSICAL JOURNAL Greenberg, J. M., Gillette, J. S., Caro, G. M., Mahajan, T. B., Zare, R. N., Li, A. G., Schutte, W. A., de Groot, M., Mendoza-Gomez, C. 2000; 531 (1): L71-L73

    View details for Web of Science ID 000086105900018

  • Separation of related opiate compounds using capillary electrochromatography ELECTROPHORESIS Lim, J. T., Zare, R. N., Bailey, C. G., Rakestraw, D. J., Yan, C. 2000; 21 (4): 737-742

    Abstract

    Capillary electrophoretic separations have been investigated for six controlled narcotic analgesic compounds having related structures. Owing to the similar charge-to-mass ratios of these compounds, capillary zone electrophoresis failed to provide a satisfactory separation, whereas a baseline-resolved separation was achieved in 10 min using micellar electrokinetic chromatography. Column efficiencies of 40,000-150,000 plates/m were obtained with a 50 cm long, 50 microm inner diameter (ID) capillary using 50 mM sodium dodecyl sulfate (SDS) in a 50 mM borate solution containing 12% isopropanol. In contrast, separation of this mixture by capillary electrochromatography proved to be significantly superior. The capillary was 15 cm long, with an ID of 75 microm, and was packed with 1.5 microm nonporous octadecyl silica (ODS) particles. The mobile phase consisted of 80% 10 mM tris(hydroxymethyl)aminomethane (Tris) and 20% acetonitrile, and contained 5 mM SDS. A complete separation was obtained in 2.5 min with an efficiency of 250,000-500,000 plates/m.

    View details for Web of Science ID 000085779400008

    View details for PubMedID 10733214

  • A laser-locked cavity ring-down spectrometer employing an analog detection scheme 8th International Conference on Ion Sources (ICIS 99) Spence, T. G., Harb, C. C., Paldus, B. A., Zare, R. N., Willke, B., Byer, R. L. AMER INST PHYSICS. 2000: 347–53

    View details for Web of Science ID 000085115100005

  • Scattering of xenon from Ni(111): Collision-induced corrugation and energy transfer dynamics JOURNAL OF CHEMICAL PHYSICS Ellison, M. D., Matthews, C. M., Zare, R. N. 2000; 112 (4): 1975-1983

    View details for Web of Science ID 000084776000038

  • Cl + HD (v=1; J=1,2) reaction dynamics: Comparison between theory and experiment JOURNAL OF CHEMICAL PHYSICS Kandel, S. A., Alexander, A. J., Kim, Z. H., Zare, R. N., Aoiz, F. J., Banares, L., Castillo, J. F., Rabanos, V. S. 2000; 112 (2): 670-685

    View details for Web of Science ID 000084507000021

  • Manipulating the genetic identity and biochemical surface properties of individual cells with electric-field-induced fusion PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Stromberg, A., Ryttsen, F., Chiu, D. T., Davidson, M., Eriksson, P. S., Wilson, C. F., Orwar, O., Zare, R. N. 2000; 97 (1): 7-11

    Abstract

    A method for cell-cell and cell-liposome fusion at the single-cell level is described. Individual cells or liposomes were first selected and manipulated either by optical trapping or by adhesion to a micromanipulator-controlled ultramicroelectrode. Spatially selective fusion of the cell-cell or cell-liposome pair was achieved by the application of a highly focused electric field through a pair of 5-micrometer o.d. carbon-fiber ultramicroelectrodes. The ability to fuse together single cells opens new possibilities in the manipulation of the genetic and cellular makeup of individual cells in a controlled manner. In the study of cellular networks, for example, the alteration of the biochemical identity of a selected cell can have a profound effect on the behavior of the entire network. Fusion of a single liposome with a target cell allows the introduction of the liposomal content into the cell interior as well as the addition of lipids and membrane proteins onto the cell surface. This cell-liposome fusion represents an approach to the manipulation of the cytoplasmic contents and surface properties of single cells. As an example, we have introduced a membrane protein (gamma-glutamyltransferase) reconstituted in liposomes into the cell plasma membrane.

    View details for Web of Science ID 000084624500004

    View details for PubMedID 10618361

    View details for PubMedCentralID PMC26606

  • Evidence for scattering resonances in the H+D-2 reaction ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Fernandez-Alonso, F., Bean, B. D., Ayers, J. D., Pomerantz, A. E., Zare, R. N., Banares, L., Aoiz, F. J. 2000; 39 (15): 2748-2752

    View details for Web of Science ID 000088702200025

  • Spatially resolved measurements of CH concentration and temperature in a hot-filament CVD reactor 6th International Symposium on Diamond Materials at the 196th Meeting of the Electrochemical-Society Wahl, E. H., Owano, T. G., Kruger, C. H., Lommatzsch, U., Aderhold, D., Zare, R. N. ELECTROCHEMICAL SOCIETY INC. 2000: 80–90

    View details for Web of Science ID 000089239900009

  • Scattering of N2 from Ni(111) Surface Science Matthews, C. M., Balzer, F., Hallock, A. J., Ellison, M. D., Zare, R. N. 2000; 460: 12-20
  • New scheme for measuring the angular momentum spatial anisotropy of vibrationally excited H-2 via the I (1)Pi(g) state ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS Fernandez-Alonso, F., Bean, B. D., Ayers, J. D., Pomerantz, A. E., Zare, R. N. 2000; 214: 1167-1186

    View details for Web of Science ID 000089661000001

  • Novel separation method on a chip using capillary electrophoresis in combination with dielectrophoresis 4th International Symposium on Micro Total Analysis Systems ((mu)TAS 2000) Morishima, K., Arnold, D. W., Wheeler, A. R., Rakestraw, D. J., Zare, R. N. SPRINGER. 2000: 269–272

    View details for Web of Science ID 000167335400061

  • Orientation as a Probe of Photodissociation Dynamics Faraday Discuss. Kim, Z. H., Alexander, A. J., Kandel, S. A., Rakitzis, T. P., Zare, R. N. 2000; 113: 27-36
  • Speed-dependent photofragment orientation in the photodissociation of OCS at 223 nm JOURNAL OF PHYSICAL CHEMISTRY A Kim, Z. H., Alexander, A. J., Zare, R. N. 1999; 103 (49): 10144-10148

    View details for Web of Science ID 000084318700013

  • Relationship between bipolar moments and molecule-frame polarization parameters in Doppler photofragment spectroscopy JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Hall, G. E., Costen, M. L., Zare, R. N. 1999; 111 (19): 8751-8754

    View details for Web of Science ID 000083437400001

  • Demonstration of optical rotatory dispersion of sucrose JOURNAL OF CHEMICAL EDUCATION Mahurin, S. M., Compton, R. N., Zare, R. N. 1999; 76 (9): 1234-1236

    View details for Web of Science ID 000082149300024

  • Reaction of state-selected ammonia ions with methane JOURNAL OF CHEMICAL PHYSICS Everest, M. A., Poutsma, J. C., Flad, J. E., Zare, R. N. 1999; 111 (6): 2507-2512

    View details for Web of Science ID 000081711200019

  • Differential cross sections for H+D-2 -> HD (v '=2, J '=0,3,5)+D at 1.55 eV JOURNAL OF CHEMICAL PHYSICS Fernandez-Alonso, F., Bean, B. D., Zare, R. N. 1999; 111 (6): 2490-2498

    View details for Web of Science ID 000081711200017

  • Manipulating the biochemical nanoenvironment around single molecules contained within vesicles CHEMICAL PHYSICS Chiu, D. T., Wilson, C. F., Karlsson, A., Danielsson, A., Lundqvist, A., Stromberg, A., Ryttsen, F., Davidson, M., Nordholm, S., Orwar, O., Zare, R. N. 1999; 247 (1): 133-139

    View details for Web of Science ID 000082303000013

  • Measurement of the HD(v '=2,J '=3) product differential cross section for the H+D-2 exchange reaction at 1.55 +/- 0.05 eV using the photoloc technique JOURNAL OF CHEMICAL PHYSICS Fernandez-Alonso, F., Bean, B. D., Zare, R. N. 1999; 111 (3): 1022-1034

    View details for Web of Science ID 000081309100028

  • Differential cross sections for H+D-2 -> HD(v(')=1, J(')=1,5,8)+D at 1.7 eV JOURNAL OF CHEMICAL PHYSICS Fernandez-Alonso, F., Bean, B. D., Zare, R. N. 1999; 111 (3): 1035-1042

    View details for Web of Science ID 000081309100029

  • State-selected studies of the reaction of NH3+ (nu(1),nu(2)) with D-2 CHEMICAL PHYSICS LETTERS Poutsma, J. C., Everest, M. A., Flad, J. E., Jones, G. C., Zare, R. N. 1999; 305 (5-6): 343-347

    View details for Web of Science ID 000080630800005

  • Direct observation of polycyclic aromatic hydrocarbons on geosorbents at the subparticle scale ENVIRONMENTAL SCIENCE & TECHNOLOGY Gillette, J. S., Luthy, R. G., Clemett, S. J., Zare, R. N. 1999; 33 (8): 1185-1192

    View details for Web of Science ID 000079974600007

  • Chemical transformations in individual ultrasmall biomimetic containers SCIENCE Chiu, D. T., Wilson, C. F., Ryttsen, F., Stromberg, A., Farre, C., Karlsson, A., Nordholm, S., Gaggar, A., Modi, B. P., Moscho, A., Garza-Lopez, R. A., Orwar, O., Zare, R. N. 1999; 283 (5409): 1892-1895

    Abstract

    Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes.

    View details for Web of Science ID 000079228600040

    View details for PubMedID 10082457

  • UV irradiation of polycyclic aromatic hydrocarbons in ices: Production of alcohols, quinones, and ethers SCIENCE Bernstein, M. P., Sandford, S. A., Allamandola, L. J., Gillette, J. S., Clemett, S. J., Zare, R. N. 1999; 283 (5405): 1135-1138

    Abstract

    Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis.

    View details for Web of Science ID 000078738400042

    View details for PubMedID 10024233

  • Measurements of Cl-atom photofragment angular momentum distributions in the photodissociation of Cl-2 and ICl JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Kandel, S. A., Alexander, A. J., Kim, Z. H., Zare, R. N. 1999; 110 (7): 3351-3359

    View details for Web of Science ID 000078446100011

  • Photofragment angular momentum distributions in the molecular frame: Determination and interpretation JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Zare, R. N. 1999; 110 (7): 3341-3350

    View details for Web of Science ID 000078446100010

  • Photoacoustic spectroscopy using quantum-cascade lasers OPTICS LETTERS Paldus, B. A., Spence, T. G., Zare, R. N., Oomens, J., Harren, F. J., Parker, D. H., Gmachl, C., Cappasso, F., Sivco, D. L., Baillargeon, J. N., Hutchinson, A. L., Cho, A. Y. 1999; 24 (3): 178-180

    Abstract

    Photoacoustic spectra of ammonia and water vapor were recorded by use of a continuous-wave quantum-cascade distributed-feedback (QC-DFB) laser at 8.5 mum with a 16-mW power output. The gases were flowed through a cell that was resonant at 1.6 kHz, and the QC-DFB source was temperature tuned over 35 nm for generation of spectra or was temperature stabilized on an absorption feature peak to permit real-time concentration measurements. A detection limit of 100 parts in 10(9) by volume ammonia at standard temperature and pressure was obtained for a 1-Hz bandwidth in a measurement time of 10 min.

    View details for Web of Science ID 000078480400020

    View details for PubMedID 18071446

  • Pulse-stacked cavity ring-down spectroscopy REVIEW OF SCIENTIFIC INSTRUMENTS Crosson, E. R., Haar, P., Marcus, G. A., Schwettman, H. A., Paldus, B. A., Spence, T. G., Zare, R. N. 1999; 70 (1): 4-10

    View details for Web of Science ID 000078186800002

  • Voltage-clamp biosensors for capillary electrophoresis. Methods in enzymology Orwar, O., Jardemark, K., Farre, C., Jacobson, I., Moscho, A., Shear, J. B., Fishman, H. A., Lillard, S. J., Zare, R. N. 1999; 294: 189-208

    View details for PubMedID 9916228

  • Orientation as a probe of photodissociation dynamics FARADAY DISCUSSIONS Kim, Z. H., Alexander, A. J., Kandel, S. A., Rakitzis, T. P., Zare, R. N. 1999; 113: 27-36

    View details for Web of Science ID 000083334200002

  • Absorption Spectroscopies: From Early Beginnings to Cavity Ring-Down Spectroscopy Cavity-Ringdown Spectroscopy--An Ultratrace-Absorption Measurement Technique Paldus, B. A., Zare, R. N. edited by Busch, K. W., Busch, M. A. American Chemical Society: Washington, DC. 1999: 49–70
  • Historical Overview of Spectral Studies: From Sunlight to Lasers Cavity-Ringdown Spectroscopy--An Ultratrace-Absorption Measurement Technique Paldus, B. A., Zare, R. N. edited by Busch, K. W., Busch, M. A. American Chemical Society: Washington, DC. 1999: 1–6
  • Reaction dynamics of atomic chlorine with methane: Importance of methane bending and torsional excitation in controlling reactivity JOURNAL OF CHEMICAL PHYSICS Kandel, S. A., Zare, R. N. 1998; 109 (22): 9719-9727

    View details for Web of Science ID 000077276000013

  • Preparation and characterization of monolithic porous capillary columns loaded with chromatographic particles ANALYTICAL CHEMISTRY Dulay, M. T., Kulkarni, R. P., Zare, R. N. 1998; 70 (23): 5103-5107

    Abstract

    Using sol-gel technology, a porous glass matrix (xerogel) is formed in a capillary column and acts as a support for a stationary phase of chromatographic particles used in capillary electrochromatography. Preparation of the sol-gel matrix and immobilization of the octadecylsilica (ODS) stationary phase occur in a single step. The presence of the particles in the column greatly reduces matrix cracking caused by internal pressure differentials within the pores of the sol-gel matrix. Good electroosmotic flow is achieved in part because of the inherent negative charge of both the particles and the sol-gel matrix. The performance of these sol-gel/ODS capillary columns was evaluated with a mixture of aromatic and nonaromatic organic compounds. Efficiencies of up to 80 000 plates/m were observed in columns with immobilized 3-μm ODS particles. The efficiency and resolution are enhanced when 3-μm ODS particles are used in place of the 5-μm particles.

    View details for Web of Science ID 000077278700046

    View details for PubMedID 21644688

  • Vibrational and translational energy effects in the reaction of ammonia ions with water molecules JOURNAL OF PHYSICAL CHEMISTRY A Everest, M. A., Poutsma, J. C., Zare, R. N. 1998; 102 (47): 9593-9598

    View details for Web of Science ID 000078514000040

  • Advances in capillary electrochromatography: Rapid and high-efficiency separations of PAHs 1997 Pittsburgh Conference Dadoo, R., Zare, R. N., Yan, C., Anex, D. S. AMER CHEMICAL SOC. 1998: 4787–92

    View details for Web of Science ID 000077003600021

  • Observation of indigenous polycyclic aromatic hydrocarbons in 'giant' carbonaceous Antarctic micrometeorites 1996 ISSOL Meeting Clemett, S. J., Chillier, X. D., Gillette, S., Zare, R. N., Maurette, M., Engrand, C., Kurat, G. SPRINGER. 1998: 425–48

    Abstract

    Two-step laser desorption/laser ionization mass spectrometry (microL2 MS) was used to establish the nature and mass distribution of polycyclic aromatic hydrocarbons (PAHs) in fragments of fifteen 'giant' (approximately 200 microns) carbonaceous Antarctic micrometeorites (AMMs). Detectable concentrations of PAHs were observed in all AMMs showing a fine-grained matrix. The range of integrated PAH signal intensities varied between samples by over two orders of magnitude. No evidence of contamination whilst in the Antarctic environment could be found. The dramatic variation of both PAH signal intensities and mass distributions between AMMs along with comprehensive contamination checks demonstrates that particles are not exposed to terrestrial PAHs at or above detection limits, either subsequent, during or prior to collection. Comparison of the observed PAH distributions with those measured in three carbonaceous chondrites [Orgueil (CI1), Murchison (CM2) and Allende (CV3)] under identical conditions demonstrated that marked differences exist in the trace organic composition of these two sources of extraterrestrial matter. In general, AMMs show a far richer distribution of unalkylated 'parent' PAHs with more extended alkylation series (replacement of -H with -(CH2)n-H; n = 1, 2, 3 ...). The degree of alkylation loosely correlates with a metamorphic index that represents the extent of frictional heating incurred during atmospheric entry. A search for possible effects of the chemical composition of the fine-grain matrix of host particles on the observed PAH distributions reveals that high degrees of alkylation are associated with high Na/Si ratios. These results, in addition to other observations by Maurette, indicate that 'giant' micrometeorites survive hypervelocity (> or = 11 km s-1) atmospheric entry unexpectedly well. Because such micrometeorites are believed to represent the dominant mass fraction of extraterrestrial material accreted by the Earth, they may have played a significant role in the prebiotic chemical evolution of the early Earth through the delivery of complex organic matter to the surface of the planet.

    View details for Web of Science ID 000075658100006

    View details for PubMedID 9742724

  • Hadamard transform time of flight mass spectrometry ANALYTICAL CHEMISTRY Brock, A., Rodriguez, N., Zare, R. N. 1998; 70 (18): 3735-3741

    View details for Web of Science ID 000075911500003

  • Separation and characterization of amines from individual atrial gland vesicles of Aplysia californica ANALYTICAL CHEMISTRY Lillard, S. J., Chiu, D. T., Scheller, R. H., Zare, R. N., Rodriguez-Cruz, S. E., Williams, E. R., Orwar, O., SANDBERG, M., Lundqvist, J. A. 1998; 70 (17): 3517-3524

    Abstract

    Several amine-containing components of individual vesicles from the atrial gland of Aplysia californica were identified with capillary electrophoresis (CE). On-line derivatization with naphthalene-2,3-dicarboxaldehyde was performed, and the derivatized amine-containing components were detected with laser-induced fluorescence (LIF). Amino acids, including taurine, that had not been determined previously in atrial gland vesicles were observed by using CE-LIF, and their identities were confirmed with CE, HPLC, NMR, and electrospray ionization mass spectrometry. The finding that taurine is packaged and stored into secretory vesicles supports the hypothesis that taurine may exhibit neuromodulatory activity. The bioactive peptides, well-known to be in atrial gland vesicles, were detected in lysed vesicle samples fractionated with HPLC and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. These peptides were also observed in single-vesicle runs with CE-LIF. The atrial gland vesicles (ranging from 0.5 to 2 microns diameter and 65 aL to 4 fL volume, respectively) studied in this work represent the smallest biological entities to be analyzed chemically on an individual basis.

    View details for Web of Science ID 000075680000007

    View details for PubMedID 9737203

  • Anatomy of elementary chemical reactions JOURNAL OF CHEMICAL EDUCATION Alexander, A. J., Zare, R. N. 1998; 75 (9): 1105-1118

    View details for Web of Science ID 000075421900021

  • Photofragment helicity caused by matter-wave interference from multiple dissociative states SCIENCE Rakitzis, T. P., Kandel, S. A., Alexander, A. J., Kim, Z. H., Zare, R. N. 1998; 281 (5381): 1346-1349

    View details for Web of Science ID 000075666800048

  • Indigenous polycyclic aromatic hydrocarbons in circumstellar graphite grains from primitive meteorites ASTROPHYSICAL JOURNAL Messenger, S., Amari, S., Gao, X., Walker, R. M., Clemett, S. J., Chillier, X. D., Zare, R. N., Lewis, R. S. 1998; 502 (1): 284-295

    View details for Web of Science ID 000077743300025

  • Electrically floating conductivity detection system for capillary electrophoresis JOURNAL OF CHROMATOGRAPHY A Zhao, H., Dadoo, R., Reay, R. J., Kovacs, G. T., Zare, R. N. 1998; 813 (1): 205-208

    View details for Web of Science ID 000074862100022

  • Optical heterodyne detection in cavity ring-down spectroscopy CHEMICAL PHYSICS LETTERS Levenson, M. D., Paldus, B. A., Spence, T. G., Harb, C. C., Harris, J. S., Zare, R. N. 1998; 290 (4-6): 335-340

    View details for Web of Science ID 000074715000007

  • Screening of receptor antagonists using agonist-activated patch clamp detection in chemical separations ANALYTICAL CHEMISTRY Jardemark, K., Farre, C., Jacobson, I., Zare, R. N., Orwar, O. 1998; 70 (13): 2468-2474

    Abstract

    We present a capillary electrophoresis-patch clamp detection system optimized for screening of antagonists and inhibitors of ligand-gated ion channels. In this system, highly selective receptor agonists are delivered through the electrophoresis capillary to the cell surface where they continuously activate a receptor, resulting in increased steady-state transmembrane currents. Thus, receptor selection and biosensor functionality is simply achieved by selection of an appropriate agonist. The antagonists are fractionated in the same electrophoresis capillary and inhibit the agonist-evoked response, resulting in transiently decreased steady-state transmembrane currents. Specifically, a mixture containing 6-cyano-7-nitroquinoxaline-2,3-dione, that reversibly blocks alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and kainate receptors, and 6,7-dichloro-3-hydroxy-2-quinoxaline-carboxylate, a broad-spectrum glutamate receptor antagonist, were separated and detected by kainate-activated patch-clamped interneurons freshly dissociated from rat brain olfactory bulb. In addition, Mg2+ that reversibly blocks the N-methyl-D-aspartate receptor in a voltage-dependent way was detected using the same cell detector system when activated by N-methyl-D-aspartate and the co-agonist glycine. The presented method offers new possibilities for drug screening and for identifying endogenous receptor antagonists and to determine their mode of action on any ionotropic receptor system of interest.

    View details for Web of Science ID 000074584700034

    View details for PubMedID 9666721

  • Photolysis of ICl causes mass-dependent interference in the Cl(P-2(3/2)) photofragment angular momentum distributions JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Kandel, S. A., Zare, R. N. 1998; 108 (20): 8291-8294

    View details for Web of Science ID 000075255700001

  • Cavity-locked ring-down spectroscopy JOURNAL OF APPLIED PHYSICS Paldus, B. A., Harb, C. C., Spence, T. G., Wilke, B., Xie, J., Harris, J. S., Zare, R. N. 1998; 83 (8): 3991-3997

    View details for Web of Science ID 000073273900006

  • Assaying for peptides in individual Aplysia neurons with mass spectrometry PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Chiu, D. T., Zare, R. N. 1998; 95 (7): 3338-3340

    View details for Web of Science ID 000072848500003

    View details for PubMedID 9520363

    View details for PubMedCentralID PMC33846

  • Angular distributions for the Cl+C2H6 -> HCl+C2H5 reaction observed via multiphoton ionization of the C2H5 radical JOURNAL OF PHYSICAL CHEMISTRY A Kandel, S. A., Rakitzis, T. P., Lev-On, T., Zare, R. N. 1998; 102 (13): 2270-2273

    View details for Web of Science ID 000072904300004

  • Laser control of chemical reactions SCIENCE Zare, R. N. 1998; 279 (5358): 1875-1879

    View details for Web of Science ID 000072613300031

  • Near-infrared cavity ringdown spectroscopy of water-vapor in an atmospheric flame CHEMICAL PHYSICS LETTERS Xie, J., Paldus, B. A., Wahl, E. H., Martin, J., Owano, T. G., Kruger, C. H., Harris, J. S., Zare, R. N. 1998; 284 (5-6): 387-395

    View details for Web of Science ID 000072935500015

  • Probing single secretory vesicles with capillary electrophoresis SCIENCE Chiu, D. T., Lillard, S. J., Scheller, R. H., Zare, R. N., Rodriguez-Cruz, S. E., Williams, E. R., Orwar, O., SANDBERG, M., Lundqvist, J. A. 1998; 279 (5354): 1190-1193

    Abstract

    Secretory vesicles obtained from the atrial gland of the gastropod mollusk Aplysia californica were chemically analyzed individually with a combination of optical trapping, capillary electrophoresis separation, and a laser-induced fluorescence detection. With the use of optical trapping, a single vesicle that had attoliters (10(-18) liters) of volume was introduced into the tapered inlet of a separation capillary. Once the vesicle was injected, it was lysed, and its components were fluorescently labeled with naphthalene-2, 3-dicarboxaldehyde before separation. The resultant electropherograms indicated distinct variations in the contents of single vesicles.

    View details for Web of Science ID 000072115200037

    View details for PubMedID 9469805

  • Voltage Clamp Biosensors for Capillary Electrophoresis Methods in Enzymology Orwar, O., Jardemark, K., Farre, C., Jacobson, I., Moscho, A., Shear, J. B., Fishman, H. A., Lillard, S. J., Zare, R. N. 1998
  • Biosensors in chemical separations ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE Fishman, H. A., Greenwald, D. R., Zare, R. N. 1998; 27: 165-198

    Abstract

    Identification of biomolecules in complex biological mixtures represents a major challenge in biomedical, environmental, and chemical research today. Chemical separations with traditional detection schemes such as absorption, fluorescence, refractive index, conductivity, and electrochemistry have been the standards for definitive identifications of many compounds. In many instances, however, the complexity of the biomixture exceeds the resolution capability of chemical separations. Biosensors based on molecular recognition can dramatically improve the selectivity of and provide biologically relevant information about the components. This review describes how coupling chemical separations with online biosensors solves challenging problems in sample analysis by identifying components that would not normally be detectable by either technique alone. This review also presents examples and principles of combining chemical separations with biosensor detection that uses living systems, whole cells, membrane receptors, enzymes, and immunosensors.

    View details for Web of Science ID 000074324000008

    View details for PubMedID 9646866

  • Companion to Angular Momentum Kleiman, D., Park, H., Gordon, R. J., Zare, R. N. John Wiley & Sons: New York. 1998
  • Evidence for the extraterrestrial origin of polycyclic aromatic hydrocarbons in the Martian meteorite ALH84001 General Discussion on Chemistry and Physics of Molecules and Grains in Space Clemett, S. J., Dulay, M. T., Gillette, J. S., Chillier, X. D., Mahajan, T. B., Zare, R. N. ROYAL SOC CHEMISTRY. 1998: 417–436

    Abstract

    Possible sources of terrestrial contamination are considered for the observation of polycyclic aromatic hydrocarbons (PAHs) in the Martian meteorite ALH84001. Contamination is concluded to be negligible.

    View details for Web of Science ID 000076353800024

    View details for PubMedID 9809015

  • Electrically Floating Conductivity Detection System for Capillary Electrophoresis Journal of Chromatography A Zhao, H., Dadoo, R., Reay, R. J., Kovacs, G. T. A., Zare, R. N. 1998; 813 (1): 205 - 208
  • Differential cross section polarization moments: Location of the D-atom transfer in the transition-state region for the reactions Cl+C2D6->DCl(v'=0,J'=1)+C2D5 and Cl+CD4->DCl(v'=0,J'=1)+CD3 JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Kandel, S. A., LevOn, T., Zare, R. N. 1997; 107 (22): 9392-9405

    View details for Web of Science ID A1997YJ04300013

  • Determination of differential-cross-section moments from polarization-dependent product velocity distributions of photoinitiated bimolecular reactions JOURNAL OF CHEMICAL PHYSICS Rakitzis, T. P., Kandel, S. A., Zare, R. N. 1997; 107 (22): 9382-9391

    View details for Web of Science ID A1997YJ04300012

  • Rate constants and products for the reaction of HBr+ with HBr and DBr CHEMICAL PHYSICS LETTERS Green, R. J., Xie, J., Zare, R. N., Viggiano, A. A., Morris, R. A. 1997; 277 (1-3): 1-5

    View details for Web of Science ID A1997YC09400001

  • Laser diode cavity ring-down spectroscopy using acousto-optic modulator stabilization JOURNAL OF APPLIED PHYSICS Paldus, B. A., Harris, J. S., Martin, J., Xie, J., Zare, R. N. 1997; 82 (7): 3199-3204

    View details for Web of Science ID A1997XY05700005

  • Nonequilibrium in thermal plasmas with applications to diamond synthesis XXIIIrd International Conference on Phenomena in Ionized Gases Kruger, C. H., Owano, T. G., Laux, C. O., Zare, R. N. EDP SCIENCES S A. 1997: 67–92

    View details for Web of Science ID 000071769900007

  • Packed column capillary electrochromatography: Advances in single column and multiple column techniques. Anex, D. S., Neyer, D. W., Zare, R. N., Zhao, H. AMER CHEMICAL SOC. 1997: 179-ANYL

    View details for Web of Science ID A1997XQ85700435

  • Patch clamp detection in capillary electrophoresis ANALYTICAL CHEMISTRY Jardemark, K., Orwar, O., Jacobson, I., Moscho, A., Zare, R. N. 1997; 69 (17): 3427-3434

    Abstract

    We describe a capillary electrophoresis-patch clamp (CE-PC) analysis of biomolecules that activate ligand-gated ion channels. CE-PC offers a powerful means for identifying receptor ligands based on the combination of the characteristic receptor responses they evoke and their differential electrophoretic migration rates. Corner frequencies, membrane reversal potentials, and mean and unitary single-channel receptor responses were calculated from currents recorded with patch clamp detection. This information was then combined with the electrophoretic mobility of the receptor ligand, which is proportional to the charge-to-frictional-drag ratio of that species. We applied CE-PC to separate and detect the endogenous receptor agonists gamma-aminobutyrate and L-glutamate and the synthetic glutamate receptor agonists N-methyl-D-aspartate and kainic acid. We present dose-response data for electrophoretically separated kainic acid and discuss its implications for making the CE-PC detection system quantitative.

    View details for Web of Science ID A1997XU10100009

    View details for PubMedID 9286160

  • Measurement of the rotational distribution for the OD product from the reaction ND3++D2O->ND4++OD JOURNAL OF CHEMICAL PHYSICS Green, R. J., Zare, R. N. 1997; 107 (3): 772-778

    View details for Web of Science ID A1997XK17900012

  • Advances toward the routine use of capillary electrochromatography LC GC-MAGAZINE OF SEPARATION SCIENCE Dadoo, R., Yan, C., Zare, R. N., Anex, D. S., Rakestraw, D. J., Hux, G. A. 1997; 15 (7): 630-?

    View details for Web of Science ID A1997XK06600006

  • Formation of a reverse parabolic flow profile with electroosmosis in capillary zone electrophoresis and the behavior of zone progress related to the application of a pulsed electric field BUNSEKI KAGAKU Tsuda, T., Kitagawa, S., Dadoo, R., Zare, R. N. 1997; 46 (6): 409-414

    View details for Web of Science ID A1997XF77400001

  • Injection of ultrasmall samples and single molecules into tapered capillaries ANALYTICAL CHEMISTRY Chiu, D. T., Hsiao, A., Gaggar, A., GARZALOPEZ, R. A., Orwar, O., Zare, R. N. 1997; 69 (10): 1801-1807

    Abstract

    A novel injection scheme is described in which ultrasmall samples in the attoliter (10(-18) L) and low femtoliter (10(-15) L) range, or even single molecules, are controllably introduced into a tapered capillary so that electrophoretic separation can be carried out. To match the dimensions of the capillary inlet with that of the sample, capillary tips are tapered to an inside diameter ranging from hundreds of nanometers to a few micrometers. To inject an ultrasmall sample, optical trapping is used to immobilize and manipulate the sample in order to place it inside or next to the capillary inlet. A small controlled suction results in the loading of the sample into the capillary.

    View details for Web of Science ID A1997WX86100001

    View details for PubMedID 9164157

  • Scattering-angle resolved product rotational alignment for the reaction of Cl with vibrationally excited methane JOURNAL OF CHEMICAL PHYSICS ORREWING, A. J., Simpson, W. R., Rakitzis, T. P., Kandel, S. A., Zare, R. N. 1997; 106 (14): 5961-5971

    View details for Web of Science ID A1997WR62000018

  • Spatially resolved measurements of absolute CH3 concentration in a hot-filament reactor 7th European Conf on Diamond, Diamond-Like and Related Materials (Diamond Films 96) / 5th International Conf on the New Diamond Science and Technology (ICNDST-5) Wahl, E. H., Owano, T. G., Kruger, C. H., Ma, Y., ZALICKI, P., Zare, R. N. ELSEVIER SCIENCE SA. 1997: 476–80

    View details for Web of Science ID A1997WY50000057

  • Optical detection and manipulation of single molecules in room-temperature solutions CHEMISTRY-A EUROPEAN JOURNAL Chiu, D. T., Zare, R. N. 1997; 3 (3): 335-339

    View details for Web of Science ID A1997WW25400002

  • Two-color resonant four-wave mixing: Analytical expressions for signal intensity JOURNAL OF CHEMICAL PHYSICS Williams, S., Rohlfing, E. A., Rahn, L. A., Zare, R. N. 1997; 106 (8): 3090-3102

    View details for Web of Science ID A1997WH84300011

  • Rotationally resolved photoelectron spectra from vibrational autoionization of NO rydberg levels JOURNAL OF CHEMICAL PHYSICS Park, H., Zare, R. N. 1997; 106 (6): 2239-2247

    View details for Web of Science ID A1997WG30700021

  • Dynamical effects of reagent vibrational excitation in the Cl+C2H6(nu(5)=1)->HCl+C2H5 reaction CHEMICAL PHYSICS LETTERS Kandel, S. A., Rakitzis, T. P., LevOn, T., Zare, R. N. 1997; 265 (1-2): 121-128

    View details for Web of Science ID A1997WF50000019

  • Microprobe two-step laser mass spectrometry as an analytical tool for meteoritic samples 178th Symposium of the International-Astronomical-Union on Molecules in Astrophysics - Probes and Processes Clemett, S. J., Zare, R. N. SPRINGER. 1997: 305–20

    View details for Web of Science ID A1997BJ12H00027

  • Optical detection of single molecules ANNUAL REVIEW OF BIOPHYSICS AND BIOMOLECULAR STRUCTURE Nie, S. M., Zare, R. N. 1997; 26: 567-596

    Abstract

    Recent advances in ultrasensitive instrumentation have allowed for the detection, identification, and dynamic studies of single molecules in the condensed phase. This measurement capability provides a new set of tools for scientists to address important current problems and to explore new frontiers in many scientific disciplines, such as chemistry, molecular biology, molecular medicine, and nanostructured materials. This review focuses on the methodologies and biological applications of single-molecule detection based on laser-induced fluorescence.

    View details for Web of Science ID A1997XD14100021

    View details for PubMedID 9241430

  • Evaluating the evidence for past life on Mars - Response SCIENCE Clemett, S. J., Zare, R. N. 1996; 274 (5295): 2122-2123

    View details for Web of Science ID A1996VY97400066

  • Measurement of rapidly varying electric fields through parity oscillations in the Rydberg states of hydrogenic atoms APPLIED PHYSICS LETTERS SHAFERRAY, N. E., Zare, R. N. 1996; 69 (24): 3749-3751

    View details for Web of Science ID A1996VW75000043

  • Dynamics for the Cl+C2H6->HCl+C2H5 reaction examined through state-specific angular distributions JOURNAL OF CHEMICAL PHYSICS Kandel, S. A., Rakitzis, T. P., LevOn, T., Zare, R. N. 1996; 105 (17): 7550-7559

    View details for Web of Science ID A1996VP28800030

  • Rapid preparation of giant unilamellar vesicles PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Moscho, A., Orwar, O., Chiu, D. T., Modi, B. P., Zare, R. N. 1996; 93 (21): 11443-11447

    Abstract

    We report here a rapid evaporation method that produces in high yield giant unilamellar vesicles up to 50 microns in diameter. The vesicles are obtained after only 2 min and can be prepared from different phospholipids, including L-alpha-phosphatidylcholine (lecithin), dipalmitoleoyl L-alpha-phosphatidylcholine, and beta-arachidonoyl gamma-palmitoyl L-alpha-phosphatidylcholine. Vesicles can be produced in distilled water and in Hepes, phosphate, and borate buffers in the pH range of 7.0 to 11.5 with ionic strengths up to 50 mM. The short preparation time allows encapsulation of labile molecular targets or enzymes with high catalytic activities. Cell-sized proteoliposomes have been prepared in which gamma-glutamyltransferase (EC 2.3.2.2) was functionally incorporated into the membrane wall.

    View details for Web of Science ID A1996VM68100028

    View details for PubMedID 8876154

    View details for PubMedCentralID PMC38076

  • Gradient elution in capillary electrochromatography ANALYTICAL CHEMISTRY Yan, C., Dadoo, R., Zare, R. N., Rakestraw, D. J., Anex, D. S. 1996; 68 (17): 2726-2730

    Abstract

    In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with submicroliter per minute flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-μm reversed-phase particles. The inlet of one capillary arm is placed in a solution reservoir containing one mobile phase, and the inlet of the other is placed in a second reservoir containing a second mobile phase. Two independent computer-controlled, programmable, high-voltage power supplies (0-50 kV) [Formula: see text] one providing an increasing ramp and the other providing a decreasing ramp [Formula: see text] are used to apply variable high-voltage potentials to the mobile phase reservoirs to regulate the electroosmotic flow in each arm. The ratio of the electroosmotic flow rates between the two arms is changed with time according to the computer-controlled voltages to deliver the required gradient profile to the separation column. Experiments were performed to confirm the composition of the mobile phase during a gradient run and to determine the change of the composition in response to the programmed voltage profile. To demonstrate the performance of electroosmotically driven gradient elution in CEC, a mixture of 16 polycyclic aromatic hydrocarbons was separated in less than 90 min. This gradient technique is expected to be well-suited for generating not only solvent gradients in CEC but also other types of gradients, such as pH and ionic strength gradients, in capillary electrokinetic separations and analyses.

    View details for Web of Science ID A1996VE59800009

    View details for PubMedID 21619344

  • Search for past life on Mars: Possible relic biogenic activity in Martian meteorite ALH84001 SCIENCE McKay, D. S., Gibson, E. K., ThomasKeprta, K. L., Vali, H., Romanek, C. S., Clemett, S. J., Chillier, X. D., MAECHLING, C. R., Zare, R. N. 1996; 273 (5277): 924-930

    Abstract

    Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features, including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.

    View details for Web of Science ID A1996VC67000052

    View details for PubMedID 8688069

  • Cavity ring-down spectroscopy with Fourier-transform-limited light pulses CHEMICAL PHYSICS LETTERS Martin, J., Paldus, B. A., ZALICKI, P., Wahl, E. H., Owano, T. G., Harris, J. S., Kruger, C. H., Zare, R. N. 1996; 258 (1-2): 63-70

    View details for Web of Science ID A1996VB49400010

  • Biased diffusion, optical trapping, and manipulation of single molecules in solution JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Chiu, D. T., Zare, R. N. 1996; 118 (27): 6512-6513

    View details for Web of Science ID A1996UW48500023

  • Patch-clamp detection of neurotransmitters in capillary electrophoresis SCIENCE Orwar, O., Jardemark, K., Jacobson, I., Moscho, A., Fishman, H. A., Scheller, R. H., Zare, R. N. 1996; 272 (5269): 1779-1782

    Abstract

    Gamma-aminobutyrate acid, L-glutamate, and N-methyl-D-aspartate were separated by capillary electrophoresis and detected by the use of whole-cell and outside-out patch-clamp techniques on freshly dissociated rat olfactory interneurons. These neuroactive compounds could be identified from their electrophoretic migration times, unitary channel conductances, and power spectra that yielded corner frequencies and mean single-channel conductances characteristic for each of the different agonist-receptor interactions. This technique has the sensitivity to observe the opening of a single ion channel for agonists separated by capillary electrophoresis.

    View details for Web of Science ID A1996UT11000040

    View details for PubMedID 8650575

  • Mass spectrometric detection of alkaline earth monohalide dications MOLECULAR PHYSICS Falcinelli, S., FERNANDEZALONSO, F., Kalogerakis, K. S., Zare, R. N. 1996; 88 (3): 663-672

    View details for Web of Science ID A1996UT95100007

  • Evidence for thermalization of surface-desorbed molecules at heating rates of 10(8) K/s JOURNAL OF CHEMICAL PHYSICS MAECHLING, C. R., Clemett, S. J., Engelke, F., Zare, R. N. 1996; 104 (21): 8768-8776

    View details for Web of Science ID A1996UM90900059

  • Energy and angular momentum control of the specific opacity functions in the Ba+HI->BaI+H reaction JOURNAL OF CHEMICAL PHYSICS Kalogerakis, K. S., Zare, R. N. 1996; 104 (20): 7947-7964

    View details for Web of Science ID A1996UL12500016

  • Picturing the transition-state region and understanding vibrational enhancement for the Cl+CH4->HCl+CH3 reaction JOURNAL OF PHYSICAL CHEMISTRY Simpson, W. R., Rakitzis, T. P., Kandel, S. A., LevOn, T., Zare, R. N. 1996; 100 (19): 7938-7947

    View details for Web of Science ID A1996UK16900024

  • Cell-to-cell scanning in capillary electrophoresis ANALYTICAL CHEMISTRY Fishman, H. A., Orwar, O., Allbritton, N. L., Modi, B. P., Shear, J. B., Scheller, R. H., Zare, R. N. 1996; 68 (7): 1181-1186

    Abstract

    A widespread limitation in using cell-based biosensors for repetitive chemical analysis is loss of agonist-induced response caused by receptor desensitization. We overcome this problem by scanning an array of immobilized cells underneath a capillary electrophoresis column outlet. In this way, electrophoretically fractionated components that exit the separation capillary are always directed onto cells previously unexposed to receptor agonists. To demonstrate this concept of response recovery using a scanning format, we have chosen the bradykinin B2 receptor system in the NG108-15 cell line, which is known to undergo desensitization. Whereas four subsequent injections of 250 microM bradykinin separated by 120 s are found to reduce the NG108-15 cell response markedly, scanning to new cells can fully restore the response during the separation. Furthermore, by pretesting individual NG108-15 cells for an agonist response and then later scanning back to the same cell, we achieved a 100% success rate in detecting bradykinin in subsequent electrophoretic separations.

    View details for Web of Science ID A1996UC18200023

    View details for PubMedID 8651490

  • Measurement of absolute CH3 concentration in a hot-filament reactor using cavity ring-down spectroscopy 6th European Conference on Diamond, Diamond-like and Related Materials (Diamond Films 95) Wahl, E. H., Owano, T. G., Kruger, C. H., ZALICKI, P., Ma, Y., Zare, R. N. ELSEVIER SCIENCE SA. 1996: 373–77

    View details for Web of Science ID A1996UQ32500036

  • Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle- and energy-resolved photoelectron spectroscopy .1. Formalism JOURNAL OF CHEMICAL PHYSICS Park, H., Zare, R. N. 1996; 104 (12): 4554-4567

    View details for Web of Science ID A1996UA38100022

  • Molecular-orbital decomposition of the ionization continuum for a diatomic molecule by angle- and energy-resolved photoelectron spectroscopy .2. Ionization continuum of NO JOURNAL OF CHEMICAL PHYSICS Park, H., Zare, R. N. 1996; 104 (12): 4568-4580

    View details for Web of Science ID A1996UA38100023

  • Screening for genetic mutations NATURE Carlsson, C., Jonsson, M., Norden, B., Dulay, M. T., Zare, R. N., Noolandi, J., Nielsen, P. E., TSUI, L. C., Zielenski, J. 1996; 380 (6571): 207-207

    View details for Web of Science ID A1996UB11700032

    View details for PubMedID 8637567

  • Photofragment imaging of methane JOURNAL OF CHEMICAL PHYSICS Heck, A. J., Zare, R. N., Chandler, D. W. 1996; 104 (11): 4019-4030

    View details for Web of Science ID A1996TY72800017

  • Effects of different population, orientation, and alignment relaxation rates in resonant four-wave mixing JOURNAL OF CHEMICAL PHYSICS Williams, S., Rahn, L. A., Zare, R. N. 1996; 104 (11): 3947-3955

    View details for Web of Science ID A1996TY72800009

  • Extensive electron-nuclear angular momentum exchange in vibrational autoionization of np and nf Rydberg states of NO PHYSICAL REVIEW LETTERS Park, H., Leahy, D. J., Zare, R. N. 1996; 76 (10): 1591-1594

    View details for Web of Science ID A1996TX69600009

  • H/D fragment ratio in Lyman-alpha photolysis of CH2D2 JOURNAL OF CHEMICAL PHYSICS Heck, A. J., Zare, R. N., Chandler, D. W. 1996; 104 (9): 3399-3402

    View details for Web of Science ID A1996TW80900028

  • Automated capillary electrochromatography: Reliability and reproducibility studies JOURNAL OF CHROMATOGRAPHY A Dulay, M. T., Yan, C., Rakestraw, D. J., Zare, R. N. 1996; 725 (2): 361-366

    Abstract

    The routine application of capillary electrochromatography (CEC) is demonstrated by incorporating 75 microns I.D. capillaries packed with 3 microns octadecylsilica (ODS) particles into a commercial CZE instrument. A mixture of several neutral compounds is separated into its components with an average efficiency up to 181 000 plates/m in less than 8 min. Hundreds of consecutive runs are performed over a period of weeks from which it is concluded that the reproducibility of the capacity factors is better than 2% and that CEC separations can be achieved in a reliable and routine manner.

    View details for Web of Science ID A1996UB61000015

    View details for PubMedID 8900577

  • Capillary electrochromatography: Operating characteristics and enantiomeric separations JOURNAL OF CHROMATOGRAPHY A Lelievre, F., Yan, C., Zare, R. N., Gareil, P. 1996; 723 (1): 145-156

    View details for Web of Science ID A1996TW15200016

  • Preparation and characterization of long-lived molecular Rydberg states: Application to HD JOURNAL OF CHEMICAL PHYSICS Merkt, F., Xu, H., Zare, R. N. 1996; 104 (3): 950-961

    View details for Web of Science ID A1996TQ80100017

  • Reaction Product Imaging: The H + HI Reaction Proceedings of Gas Phase Chemical Reaction Systems: Experiments & Models 100 years after Max Bodenstein Kitsopoulos, T. N., Baldwin, D. P., Chandler, D. W., Heck, A. J., McKay, R. I., Buntine, M. A., Zare, R. N. edited by Wolfrum, J., Volpp, H. P., Rannacher, T., Warnatz, J. 1996
  • Deuterium Enrichments in Cluster IDPs Lunar Planet. Sci. Conf. XXVII Messenger, S., Walker, R. M., Clemett, S. J., Zare, R. N. 1996: 867
  • Indigenous Polycyclic Aromatic Hydrocarbon Molecules in Circumstellar Graphite Grains Planet. Sci. Conf. XXVII Clemett, S. J., Chiller, X. D., Gao, X., Walker, R. M., Zare, R. N. 1996: 229
  • Photofragment imaging of Kr-2 and ArKr van der Waals molecules following two-photon excitation JOURNAL OF PHYSICAL CHEMISTRY Heck, A. J., Neyer, D. W., Zare, R. N., Chandler, D. W. 1995; 99 (50): 17700-17710

    View details for Web of Science ID A1995TK40300006

  • USE OF 2,3-NAPHTHALENEDICARBOXALDEHYDE DERIVATIZATION FOR SINGLE-CELL ANALYSIS OF GLUTATHIONE BY CAPILLARY ELECTROPHORESIS AND HISTOCHEMICAL-LOCALIZATION ION BY FLUORESCENCE MICROSCOPY ANALYTICAL CHEMISTRY Orwar, O., Fishman, H. A., Ziv, N. E., Scheller, R. H., Zare, R. N. 1995; 67 (23): 4261-4268

    Abstract

    We report that 2,3-naphthalenedicarboxaldehyde reacts rapidly with glutathione and its precursor, gamma-glutamylcysteine, to form highly fluorescent derivatives under physiological conditions. In contrast to previous accounts of 2,3-naphthalenedicarboxaldehyde labeling of primary amines, no additional CN- ion or any other additional nucleophile is required. The fluorescence spectral properties of the chromophores (lambda exc max = 472 nm, lambda em max = 528 nm) make these derivatives amenable to excitation and detection by optical instrumentation that is optimized for fluorescein wavelengths. This selective labeling chemistry enabled quantitative determination and histochemical localization of glutathione in neurobiological samples. Intracellular glutathione was labeled by incubating cultured cells or cell suspensions in a 2,3-naphthalenedicarboxaldehyde-supplemented, DMSO-containing physiological buffer (pH = 7.4) for 2-10 min. Applications include imaging of cultured NG 108-15 cells (mouse neuroblastoma x rat glioma) and primary glial and neuronal cell cocultures (rat hippocampus) using epiluminescent and confocal fluorescence microscopy. Quantitative determination of glutathione in single NG 108-15 cells was accomplished using laser-induced fluorescence detection and capillary electrophoresis.

    View details for Web of Science ID A1995TG92800015

    View details for PubMedID 8633771

  • CORE EXTRACTION FOR MEASURING STATE-TO-STATE DIFFERENTIAL-CROSS SECTIONS OF BIMOLECULAR REACTIONS JOURNAL OF CHEMICAL PHYSICS Simpson, W. R., ORREWING, A. J., Rakitzis, T. P., Kandel, S. A., Zare, R. N. 1995; 103 (17): 7299-7312

    View details for Web of Science ID A1995TB63300009

  • REACTION OF CL WITH VIBRATIONALLY EXCITED CH4 AND CHD3 - STATE-TO-STATE DIFFERENTIAL CROSS-SECTIONS AND STERIC EFFECTS FOR THE HCL PRODUCT JOURNAL OF CHEMICAL PHYSICS Simpson, W. R., Rakitzis, T. P., Kandel, S. A., ORREWING, A. J., Zare, R. N. 1995; 103 (17): 7313-7335

    View details for Web of Science ID A1995TB63300010

  • D(2)E,F-1-SIGMA(+)(G)(V'=0 AND 1)-X(1)SIGMA(+)(G)(V''=0-5) TRANSITION ENERGIES FOR J'=J''=0-26 - COMPARISON OF EXPERIMENT AND THEORY JOURNAL OF MOLECULAR SPECTROSCOPY Heck, A. J., Huo, W. M., Zare, R. N., Chandler, D. W. 1995; 173 (2): 452-462

    View details for Web of Science ID A1995RY59500011

  • MEASUREMENT OF THE STATE-SPECIFIC DIFFERENTIAL CROSS-SECTION FOR THE H+D-2-]HD(V'=4, J'=3)+D REACTION AT A COLLISION ENERGY OF 2.2 EV JOURNAL OF CHEMICAL PHYSICS Xu, H., SHAFERRAY, N. E., Merkt, F., Hughes, D. J., Springer, M., Tuckett, R. P., Zare, R. N. 1995; 103 (12): 5157-5160

    View details for Web of Science ID A1995RU87600039

  • POLYCYCLIC AROMATIC-HYDROCARBONS IN THE MARTIAN (SNC) METEORITE ALLAN-HILLS-84001 - HYDROCARBONS FROM MARS, TERRESTRIAL CONTAMINANTS, OR BOTH Thomas, K. L., Clemett, S. J., Romanek, C. S., MACHELING, C. R., Gibson, E. K., McKay, D. S., SCORE, R., Zare, R. N. METEORITICAL SOC. 1995: 587–87

    View details for Web of Science ID A1995RR51800224

  • CHEMICAL AND MINERALOGICAL STUDIES OF AN EXTREMELY DEUTERIUM-RICH IDP Messenger, S., Clemett, S. J., Keller, L. P., Thomas, K. L., Chillier, X. D., Zare, R. N. METEORITICAL SOC. 1995: 546–47

    View details for Web of Science ID A1995RR51800144

  • REAL-TIME DETECTION OF SINGLE-MOLECULES IN SOLUTION BY CONFOCAL FLUORESCENCE MICROSCOPY ANALYTICAL CHEMISTRY Nie, S. M., Chiu, D. T., Zare, R. N. 1995; 67 (17): 2849-2857

    View details for Web of Science ID A1995RR26000024

  • CAPILLARY ELECTROCHROMATOGRAPHY Yan, C., Rakestraw, D. J., Dadoo, R., Dulay, M. T., Lelievre, F., Gareil, P., Zhao, H., Zare, R. N. AMER CHEMICAL SOC. 1995: 112-ANYL

    View details for Web of Science ID A1995RP25600460

  • IDENTIFICATION OF RECEPTOR LIGANDS AND RECEPTOR SUBTYPES USING ANTAGONISTS IN A CAPILLARY ELECTROPHORESIS SINGLE-CELL BIOSENSOR SEPARATION SYSTEM PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Fishman, H. A., Orwar, O., Scheller, R. H., Zare, R. N. 1995; 92 (17): 7877-7881

    Abstract

    A capillary electrophoresis system with single-cell biosensors as a detector has been used to separate and identify ligands in complex biological samples. The power of this procedure was significantly increased by introducing antagonists that inhibited the cellular response from selected ligand-receptor interactions. The single-cell biosensor was based on the ligand-receptor binding and G-protein-mediated signal transduction pathways in PC12 and NG108-15 cell lines. Receptor activation was measured as increases in cytosolic free calcium ion concentration by using fluorescence microscopy with the intracellular calcium ion indicator fluo-3-acetoxymethyl ester. Specifically, a mixture of bradykinin (BK) and acetylcholine (ACh) was fractionated and the components were identified by inhibiting the cellular response with icatibant (HOE 140), a selective antagonist to the BK B2 receptor subtype (B2BK), and atropine, an antagonist to muscarinic ACh receptor subtypes. Structurally related forms of BK were also identified based on inhibiting B2BK receptors. Applications of this technique include identification of endogenous BK in a lysate of human hepatocellular carcinoma cells (Hep G2) and screening for bioactivity of BK degradation products in human blood plasma. The data demonstrate that the use of antagonists with a single-cell biosensor separation system aids identification of separated components and receptor subtypes.

    View details for Web of Science ID A1995RP74800057

    View details for PubMedID 7644507

  • C-13/C-12 RATIO MEASUREMENTS OF AROMATIC-MOLECULES USING PHOTOIONIZATION WITH TOF MASS-SPECTROMETRY CHEMICAL PHYSICS LETTERS MAECHLING, C. R., Clemett, S. J., Zare, R. N. 1995; 241 (4): 301-310

    View details for Web of Science ID A1995RL96600006

  • MEASUREMENT OF THE METHYL RADICAL CONCENTRATION PROFILE IN A HOT-FILAMENT REACTOR APPLIED PHYSICS LETTERS ZALICKI, P., Ma, Y., Zare, R. N., Wahl, E. H., Owano, T. G., Kruger, C. H. 1995; 67 (1): 144-146

    View details for Web of Science ID A1995RF82900049

  • AN ASTEROIDAL BRECCIA - THE ANATOMY OF A CLUSTER IDP GEOCHIMICA ET COSMOCHIMICA ACTA Thomas, K. L., BLANFORD, G. E., Clemett, S. J., Flynn, G. J., Keller, L. P., Klock, W., MAECHLING, C. R., McKay, D. S., Messenger, S., Nier, A. O., Schlutter, D. J., Sutton, S. R., Warren, J. L., Zare, R. N. 1995; 59 (13): 2797-2815

    View details for Web of Science ID A1995RL23400013

  • CAPILLARY ELECTROCHROMATOGRAPHY - ANALYSIS OF POLYCYCLIC AROMATIC-HYDROCARBONS ANALYTICAL CHEMISTRY Yan, C., Dadoo, R., Zhao, H., Zare, R. N., Rakestraw, D. J. 1995; 67 (13): 2026-2029

    View details for Web of Science ID A1995RF79200025

  • BEYOND STATE-TO-STATE DIFFERENTIAL CROSS-SECTIONS - DETERMINATION OF PRODUCT POLARIZATION IN PHOTOINITIATED BIMOLECULAR REACTIONS JOURNAL OF PHYSICAL CHEMISTRY SHAFERRAY, N. E., ORREWING, A. J., Zare, R. N. 1995; 99 (19): 7591-7603

    View details for Web of Science ID A1995QY25200046

  • ANALYSIS OF UNDERIVATIZED AMINO-ACIDS BY CAPILLARY ELECTROPHORESIS USING CONSTANT POTENTIAL AMPEROMETRIC DETECTION ELECTROPHORESIS Guo, Y., Colon, L. A., Dadoo, R., Zare, R. N. 1995; 16 (4): 493-497

    Abstract

    A mixture of native (underivatized) amino acids is separated by capillary electrophoresis under alkaline conditions (pH approximately 12) and amperometrically detected with a copper-disk microelectrode. A simple design facilitates capillary-electrode alignment without the need for micropositioning equipment. The limits of detection for the amino acids are in the low microM concentration range, and the signal response is linear over 2-3 orders of magnitude. This procedure is applied to analyze the amino acid hydrolysis products from cytochrome c.

    View details for Web of Science ID A1995QZ37600005

    View details for PubMedID 7588516

  • THROUGH THE GLASS LIGHTLY SCIENCE Weintraub, H., Ashburner, M., Goodfellow, P. N., Lodish, H. F., ARNTZEN, C. J., ANDERSON, P. W., Rice, T. M., Geballe, T. H., Means, A. R., Ranney, H. M., Cech, T. R., COLWELL, R. R., Bourne, H. R., Richter, B., Singer, I. M., Marrack, P., Fearon, D. T., Penzias, A., Bard, A. J., BRINKMAN, W. F., Marks, P. A., VOGELSTEIN, B., KINZLER, K. W., BISHOP, J. M., Zare, R. N., Schatz, G., Benkovic, S. J., Gray, H. B., Valentine, J. S., Crutzen, P. J., Choi, D. W., Nakanishi, S., Kosslyn, S. M., Brauman, J. I., Rees, D. C., BRILL, W. J., SCHELL, J., Luhrmann, R., Will, C. L., Wulf, W., Vermeij, G. J., Arrow, K. J., Smelser, N. J., Anderson, D. L., ABELSON, P. H. 1995; 267 (5204): 1609-1618

    View details for Web of Science ID A1995QM39700026

    View details for PubMedID 7886446

  • METHYL RADICAL MEASUREMENT BY CAVITY RING-DOWN SPECTROSCOPY CHEMICAL PHYSICS LETTERS ZALICKI, P., Ma, Y., Zare, R. N., Wahl, E. H., DADAMIO, J. R., Owano, T. G., Kruger, C. H. 1995; 234 (4-6): 269-274

    View details for Web of Science ID A1995QK79900001

  • CAVITY RING-DOWN SPECTROSCOPY FOR QUANTITATIVE ABSORPTION-MEASUREMENTS JOURNAL OF CHEMICAL PHYSICS ZALICKI, P., Zare, R. N. 1995; 102 (7): 2708-2717

    View details for Web of Science ID A1995QF82100005

  • SINGLE CELLS AS BIOSENSORS FOR CHEMICAL SEPARATIONS SCIENCE Shear, J. B., Fishman, H. A., Allbritton, N. L., Garigan, D., Zare, R. N., Scheller, R. H. 1995; 267 (5194): 74-77

    Abstract

    A biosensor system based on the response of living cells was demonstrated that can detect specific components of a complex mixture fractionated by a microcolumn separation technique. This system uses ligand-receptor binding and signal-transduction pathways to biochemically amplify the presence of an analyte after electrophoretic separation. The transduced signal was measured by means of two approaches: (i) fluorescence determination of intracellular calcium concentrations in one or more rat PC-12 cells and (ii) measurement of transmembrane current in a Xenopus laevis oocyte microinjected with messenger RNA that encodes a specific receptor. This analysis system has the potential to identify biologically active ligands present in a complex mixture with exceptional sensitivity and selectivity.

    View details for Web of Science ID A1995QA23500030

    View details for PubMedID 7809609

  • Organic Molecules in Interstellar Graphite Grains II Lunar Planet. Sci. Conf. Clemett, S. J., Maechling, C. R., Chen, Y., Zare, R. N., Messenger, S., Amari, S., Gao, X., Walker, R. M., Lewis, R. 1995: 259
  • Orientation and Alignment of the Products of Bimolecular Reactions The Chemical Dynamics and Kinetics of Small Radicals Orr-Ewing, A. J., Zare, R. N. edited by Liu, K., Wagner, A. World Scientific: River Edge, NJ. 1995: 936–1063
  • Hydrogen Recombinative Desorption Dynamics Laser Spectroscopy and Photochemistry on Metal Surfaces Bent, S. F., Michelsen, H. A., Zare, R. N. edited by Dai, H., Ho, W. World Scientific Pub Co., Inc.. 1995: 977–1043
  • Hydrated Cluster Particles: Chemical and Mineralogical Analyses of Fragments from Two Interplanetary Dust Particles Lunar Planet. Sci. Conf. XXVI Thomas, K. L., Keller, L. P., Clemett, S. J., McKay, D. S., Messenger, S., Zare, R. N. 1995
  • DETERMINATION OF PHOTODESTRUCTION QUANTUM YIELDS USING CAPILLARY ELECTROPHORESIS - APPLICATION TO O-PHTHALALDEHYDE-LABELED BETA-MERCAPTOETHANOL-LABELED AMINO-ACIDS JOURNAL OF LIQUID CHROMATOGRAPHY Orwar, O., Fishman, H. A., Sundahl, M., Banthia, V., Dadoo, R., Zare, R. N. 1995; 18 (18-19): 3833-3846

    View details for Web of Science ID A1995TJ40000020

  • Organic Molecules in Interstellar Graphite Grains I Lunar Planet. Sci. Conf. XXVI Messenger, S., Amari, S., Gao, X., Walker, R. M., Clemett, S. J., Maechling, C. R., Chen, Y., Zare, R. N., Lewis, R. 1995
  • Laser Experiments for Beginners Zare, R. N., Spencer, B. H., Springer, D. S., Jacobson, M. P. University Science Books. 1995
  • Preliminary Analysis of Polycyclic Aromatic Hydrocarbons in the Martian (SNC) Meteorite ALH84001 Lunar Planet. Sci. Conf. XXVI Thomas, K. L., Romanek, C. S., Clemett, S. J., Gibson, E. K., McKay, D. S., Maechling, C. R., Zare, R. N. 1995
  • PROBING INDIVIDUAL MOLECULES WITH CONFOCAL FLUORESCENCE MICROSCOPY SCIENCE Nie, S. M., Chiu, D. T., Zare, R. N. 1994; 266 (5187): 1018-1021

    Abstract

    Confocal fluorescence microscopy coupled with a diffraction-limited laser beam and a high-efficiency detection system has been used to study the diffusive movement and emission process of individual fluorescent molecules in the liquid phase at room temperature. The high detection sensitivity achieved at fast data acquisition speeds (greater than 1 kilohertz) allows real-time observation of single-molecule fluorescence without statistical analysis. The results show fluorescence-cycle saturation at the single-molecule level and multiple recrossings of a single molecule into and out of the probe volume as well as the triplet state.

    View details for Web of Science ID A1994PQ92400036

    View details for PubMedID 7973650

  • ONLINE TIME-OF-FLIGHT MASS-SPECTROMETRIC ANALYSIS OF PEPTIDES SEPARATED BY CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY Fang, L. L., Zhang, R., Williams, E. R., Zare, R. N. 1994; 66 (21): 3696-3701

    View details for Web of Science ID A1994PP23500027

  • LASER-INDUCED THERMAL GRATING EFFECTS IN FLAMES OPTICS LETTERS Williams, S., Rahn, L. A., Paul, P. H., Forsman, J. W., Zare, R. N. 1994; 19 (21): 1681-1683

    Abstract

    Light scattering from a laser-induced thermal grating produced in an atmospheric-pressure H(2)/O(2) flame is observed with a phase-matching geometry commonly used in resonant four-wave mixing and laser-induced grating spectroscopy. The presence of thermal gratings is confirmed in both the time and the frequency domains in two distinct experiments. Diluting the flame with helium decreases the thermal grating signal intensity. Experimental results agree well with calculations based on a solution of the linearized hydrodynamic equations.

    View details for Web of Science ID A1994PN86800003

    View details for PubMedID 19855620

  • PARTIAL CONTROL OF AN ION-MOLECULE REACTION BY SELECTION OF THE INTERNAL MOTION OF THE POLYATOMIC REAGENT ION SCIENCE GUETTLER, R. D., Jones, G. C., Posey, L. A., Zare, R. N. 1994; 266 (5183): 259-261

    Abstract

    The ion-molecule reaction NH(3)(+) + ND(3) has been studied at various collision energies (1 to 5 electron volts in the center of mass) with preparation of the NH(3)(+) reagent in two nearly isoenergetic vibrational states. One state corresponds to pure out-of-plane bending of the planar NH(3)(+) ion (0.60 electron volts), whereas the other state is a combination of in-plane and out-of-plane motion (0.63 electron volts). The product branching ratios differ markedly for these two vibrational-state preparations. The differences in reactivity suggest that the in-plane totally symmetric stretching mode is essentially inactive in controlling the branching ratio of this reaction.

    View details for Web of Science ID A1994PM13400028

    View details for PubMedID 17771446

  • SELECTIVE DETERMINATION OF ADENINE-CONTAINING COMPOUNDS BY CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE DETECTION ANALYTICAL BIOCHEMISTRY Tseng, H. C., Dadoo, R., Zare, R. N. 1994; 222 (1): 55-58

    Abstract

    Capillary electrophoresis coupled with laser-induced fluorescence detection provides a selective analysis of mixtures of adenine-containing compounds (adenine, adenosine, cAMP, AMP, ADP, and ATP) that are derivatized using chloroacetaldehyde as a fluorogenic reagent. The components can be detected with linear response over the concentration range of 10(-4) to 10(-9) M, and the detection limit corresponds to 5 to 10 x 10(-19) mol for each nucleotide. Analysis is achieved in less than 10 min with high separation efficiencies (up to 400,000 theoretical plates) and shows good reproducibility for migration times (0.5 to 1.0%) and peak heights (2.8 to 7.7%). To demonstrate the rapid analysis of small-volume samples, the adenine-containing compounds present in an oocyte from Xenopus laevis are determined.

    View details for Web of Science ID A1994PM43900009

    View details for PubMedID 7856871

  • DUAL ELECTROCHEMICAL DETECTION OF CYSTEINE AND CYSTINE IN CAPILLARY ZONE ELECTROPHORESIS 6th International Symposium on High Performance Capillary Electrophoresis (HPCE 94) Lin, B. L., Colon, L. A., Zare, R. N. ELSEVIER SCIENCE BV. 1994: 263–70

    View details for Web of Science ID A1994PL67300032

  • MICROCOLUMN SAMPLE INJECTION BY SPONTANEOUS FLUID DISPLACEMENT 6th International Symposium on High Performance Capillary Electrophoresis (HPCE 94) Fishman, H. A., Scheller, R. H., Zare, R. N. ELSEVIER SCIENCE BV. 1994: 99–107

    Abstract

    The withdrawal of a capillary structure from a sample solution causes a droplet to be formed at the end of the capillary. Because of the interfacial pressure difference across the curved surface of the droplet, the droplet is driven into the entrance of the capillary, thereby causing injection of the sample. Assuming negligible sample penetration by diffusive or convective mixing, this injection is intrinsically the smallest possible for a capillary. Moreover, the injection volume can be varied by changing the shape of the capillary structure, specifically the outer diameter of the capillary. This injection method eliminates the need for external pressure differences, applied fields across the capillary, or precise timing, thus offering several advantages over conventional procedures. Studies using capillary electrophoresis as the separation procedure show that approximately 3.5 nl (66 microns I.D. capillary) sample volumes can be injected by hand with a reproducibility of 5.8 +/- 0.7% R.S.D. Parameters that affect the variability of the injection are discussed.

    View details for Web of Science ID A1994PL67300013

    View details for PubMedID 7952011

  • INFLUENCE OF VIBRATIONAL-EXCITATION AND COLLISION ENERGY ON THE ION-MOLECULE REACTION NH3+(NU(2))+ND3 JOURNAL OF CHEMICAL PHYSICS Posey, L. A., GUETTLER, R. D., KIRCHNER, N. J., Zare, R. N. 1994; 101 (5): 3772-3786

    View details for Web of Science ID A1994PE11000039

  • REAL-TIME MEASUREMENT OF ELECTROOSMOTIC FLOW IN CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Lee, T. T., Dadoo, R., Zare, R. N. 1994; 66 (17): 2694-2700

    View details for Web of Science ID A1994PD71700018

  • GUIDED ION-BEAM MEASUREMENT OF THE PRODUCT BRANCHING RATIOS FOR THE ION-MOLECULE REACTION N++O-2 AS A FUNCTION OF COLLISION ENERGY JOURNAL OF CHEMICAL PHYSICS GUETTLER, R. D., Jones, G. C., Posey, L. A., KIRCHNER, N. J., Keller, B. A., Zare, R. N. 1994; 101 (5): 3763-3771

    View details for Web of Science ID A1994PE11000038

  • ON THE LIFETIMES OF RYDBERG STATES PROBED BY DELAYED PULSED-FIELD IONIZATION JOURNAL OF CHEMICAL PHYSICS Merkt, F., Zare, R. N. 1994; 101 (5): 3495-3505

    View details for Web of Science ID A1994PE11000009

  • EVIDENCE FOR A COOPER MINIMUM IN THE PHOTOIONIZATION DYNAMICS OF THE NO D2-SIGMA+ STATE CHEMICAL PHYSICS LETTERS Park, H. K., Zare, R. N. 1994; 225 (4-6): 327-334

    View details for Web of Science ID A1994PB64400006

  • SPONTANEOUS INJECTION IN MICROCOLUMN SEPARATIONS ANALYTICAL CHEMISTRY Fishman, H. A., AMUDI, N. M., Lee, T. T., Scheller, R. H., Zare, R. N. 1994; 66 (14): 2318-2329

    Abstract

    The phenomenon of spontaneous (ubiquitous) injection in microcolumn separations has been characterized to improve quantitative precision for ultramicrosampling and to enhance separation efficiency. By combining fluorescence imaging, video microscopy, and measurements from capillary electrophoresis, we demonstrate that spontaneous injection is caused primarily by an interfacial pressure difference formed at the inlet of the capillary. This complex injection mechanism has been modeled with some simple assumptions based on fluid dynamics. In particular, studies showed that extraneous injection is reduced up to 12-fold by etching the capillary inlet or by using a thin-walled capillary. Variations by a factor of 2 in the injection length can result from delays between sample introduction and reinsertion into the inlet vial if the timing is not controlled precisely. Evidence is presented that evaporation of buffer from the inlet can reduce the injection length by more than 1 order of magnitude.

    View details for Web of Science ID A1994NX05500021

    View details for PubMedID 8080106

  • REDUCTION OF DEGENERATE 4-WAVE-MIXING SPECTRA TO RELATIVE POPULATIONS .1. WEAK-FIELD LIMIT JOURNAL OF CHEMICAL PHYSICS Williams, S., Zare, R. N., Rahn, L. A. 1994; 101 (2): 1072-1092

    View details for Web of Science ID A1994NW97900024

  • REDUCTION OF DEGENERATE 4-WAVE-MIXING SPECTRA TO RELATIVE POPULATIONS .2. STRONG-FIELD LIMIT JOURNAL OF CHEMICAL PHYSICS Williams, S., Zare, R. N., Rahn, L. A. 1994; 101 (2): 1093-1107

    View details for Web of Science ID A1994NW97900025

  • MEASUREMENTS OF AROMATIC-HYDROCARBONS IN INTERSTELLAR GRAPHITE GRAINS .1. SELECTION AND ISOTOPIC MEASUREMENT OF GRAPHITE Messenger, S., Alexander, C. M. METEORITICAL SOC. 1994: 502–

    View details for Web of Science ID A1994NW88400133

  • MEASUREMENTS OF AROMATIC-HYDROCARBONS IN INTERSTELLAR GRAPHITE GRAINS .2. MOLECULAR MEASUREMENTS Clemett, S. J., MAECHLING, C. R., Zare, R. N., Messenger, S., Alexander, C. M., Gao, X., Swan, P. D., Walker, R. M. METEORITICAL SOC. 1994: 458–58

    View details for Web of Science ID A1994NW88400045

  • CORRELATION DIAGRAMS FOR HUND COUPLING CASES IN DIATOMIC-MOLECULES WITH HIGH ROTATIONAL ANGULAR-MOMENTUM MOLECULAR PHYSICS NIKITIN, E. E., Zare, R. N. 1994; 82 (1): 85-100

    View details for Web of Science ID A1994NN66200006

  • DIRECT MEASUREMENT OF THE 3-DIMENSIONAL PRODUCT VELOCITY DISTRIBUTION FROM PHOTOINITIATED BULB REACTIONS JOURNAL OF PHYSICAL CHEMISTRY SHAFER, N. E., Xu, H., Tuckett, R. P., Springer, M., Zare, R. N. 1994; 98 (13): 3369-3378

    View details for Web of Science ID A1994NE87800023

  • FIELD PROGRAMMING TO ACHIEVE UNIFORM SENSITIVITY FOR ONLINE DETECTION IN ELECTROPHORESIS ELECTROPHORESIS Shear, J. B., Dadoo, R., Zare, R. N. 1994; 15 (2): 225-227

    Abstract

    Under constant applied electric field, an analyte band traverses an on-line detection zone in an electrophoretic separation at a velocity inversely proportional to the detection time. Because analyte bands migrate with different velocities, the sensitivity of the detection system to different species can vary significantly. One approach for overcoming this problem is to change the applied electric field, E, as a function of the separation time, tau, so that the velocity of an analyte band when it passes through the detection zone is independent of the analyte's electrophoretic mobility. A possible solution is to make E(tau) grow exponentially, but this procedure causes band compression. The preferred solution is to make both E(tau) and the distance between the starting position of the sample and the detection zone increase linearly with separation time. This approach can be implemented with either slab-gel or capillary electrophoresis.

    View details for Web of Science ID A1994NB52500019

    View details for PubMedID 8026438

  • END-COLUMN CHEMILUMINESCENCE DETECTOR FOR CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY Dadoo, R., Seto, A. G., Colon, L. A., Zare, R. N. 1994; 66 (2): 303-306

    View details for Web of Science ID A1994MR31600022

  • ORIENTATION AND ALIGNMENT OF REACTION-PRODUCTS ANNUAL REVIEW OF PHYSICAL CHEMISTRY ORREWING, A. J., Zare, R. N. 1994; 45: 315-366

    View details for Web of Science ID A1994PR65600011

  • PREPARING REAGENTS - TIME-DEPENDENCE OF HCL(V=1, J) ALIGNMENT FOLLOWING PULSED INFRARED EXCITATION ISRAEL JOURNAL OF CHEMISTRY ORREWING, A. J., Simpson, W. R., Rakitzis, T. P., Zare, R. N. 1994; 34 (1): 95-102

    View details for Web of Science ID A1994NV75800013

  • Competition between Abstraction and Insertion in the Reaction Family, M(Be, Mg, Ca, Sr, Ba) + HX(HF, HCl, HBr, HI) → MX + H." Proceedings of the Robert A. Welch Foundation, 38th Conference on Chemical Research: chemical dynamics of transient species Zare, R. N., Kalogerakis, K. S. 1994
  • Reduction of Degenerate Four-Wave Mixing Spectra to Relative Populations I: Weak-Field Limit J. Chem. Phys. Williams, S., Zare, R. N., Rahn, L. A. 1994; 101: 1072-1092
  • Anatomy of a Cluster IDP (II): Noble Gas Abundances, Trace Element Geochemistry, Isotopic Abundances and Trace Organic Chemistry of Several Fragments from L2008 #5 Lunar Planet Sci. Conf. XXV Thomas, K. L., Clemett, S. J., Flynn, G. J., Keller, L. P., McKay, D. S., Messenger, S., Nier, A. O., Schlutter, D. J., Sutton, S. R., Walker, R. M., Zare, R. N. 1994: 1391
  • ULTRASENSITIVE FLUORESCENCE DETECTION OF POLYCYCLIC AROMATIC-HYDROCARBONS IN CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY Nie, S. M., Dadoo, R., Zare, R. N. 1993; 65 (24): 3571-3575

    View details for Web of Science ID A1993MM26400007

  • AUTOMATED VELOCITY PROGRAMMING FOR INCREASED DETECTION ZONE RESIDENCE TIMES IN CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY Shear, J. B., Colon, L. A., Zare, R. N. 1993; 65 (24): 3708-3712

    View details for Web of Science ID A1993MM26400026

    View details for PubMedID 7906105

  • OPTIMIZING FLUORESCENCE DETECTION IN CHEMICAL SEPARATIONS FOR ANALYTE BANDS TRAVELING AT DIFFERENT VELOCITIES ANALYTICAL CHEMISTRY Shear, J. B., Dadoo, R., Fishman, H. A., Scheller, R. H., Zare, R. N. 1993; 65 (21): 2977-2982

    Abstract

    In many separation techniques, such as field flow fractionation, liquid chromatography, and electrophoresis, chemical species form bands that migrate at distinct velocities. If these bands are to be quantified on-line using a shot-noise-limited detection system, then attention must be given to the data-digitization rate and to the removal rate of molecules from the analyte pool as a result of the detection process. A theory is developed for calculating the signal-to-noise ratio under such conditions, and it is specialized to the case of fluorescence detection in capillary electrophoresis. Using standard detection procedures in which the data-digitization rate and excitation intensity remain constant for the duration of a separation, detection sensitivity can vary by more than a factor of five for bands that arrive at the detection zone between migration times tau fast and 10 tau fast, where tau fast is the time after the start of the separation that the fastest migrating band arrives at the detection zone. To compensate for different band velocities, both the data-digitization rate and the excitation intensity must be decreased as separation time (tau) increases by the factor tau fast/tau. Only when these corrections are made can uniform sensitivity with the highest possible signal-to-noise ratio be achieved for each peak. These predictions are experimentally tested and compare favorably to observations.

    View details for Web of Science ID A1993ME46900008

    View details for PubMedID 8256862

  • PHOTOIONIZATION DYNAMICS OF THE NO A(2)SIGMA(+) STATE DEDUCED FROM ENERGY-RESOLVED AND ANGLE-RESOLVED PHOTOELECTRON-SPECTROSCOPY JOURNAL OF CHEMICAL PHYSICS Park, H., Zare, R. N. 1993; 99 (9): 6537-6544

    View details for Web of Science ID A1993MD98100034

  • IDENTIFICATION OF COMPLEX AROMATIC-MOLECULES IN INDIVIDUAL INTERPLANETARY DUST PARTICLES SCIENCE Clemett, S. J., MAECHLING, C. R., Zare, R. N., Swan, P. D., Walker, R. M. 1993; 262 (5134): 721-725

    Abstract

    Seventeen stratospherically collected particles-eight of which are classified as interplanetary dust particles (IDPs), seven of which are classified as probable terrestrial contaminants, and two of which have uncertain origins-were studied with a microprobe two-step laser mass spectrometer. Many polycyclic aromatic hydrocarbons(PAHs) and their alkylated derivatives were identified in two of the eight IDPs. The PAHs observed include a high-mass envelope not found in meteorites or terrestrial contaminants and prominent odd-mass peaks suggestive of nitrogen-containing functional groups attached to aromatic chromophores. In addition, the complexity of the IDP mass spectra has no precedence in previous studies of meteorite samples or their acid residues. Extensive checks were performed to demonstrate that the PAH signals are not caused by terrestrial contaminants.

    View details for Web of Science ID A1993MD95200035

    View details for PubMedID 17812337

  • STATE-TO-STATE DIFFERENTIAL CROSS-SECTIONS FOR THE REACTION CL((2)P(3/2))+CH4(NU-3=1,J=1)-]HCL(NU'=1,J')+CH3 CHEMICAL PHYSICS LETTERS Simpson, W. R., ORREWING, A. J., Zare, R. N. 1993; 212 (1-2): 163-171

    View details for Web of Science ID A1993LV62900028

  • STATE-TO-STATE DIFFERENTIAL CROSS-SECTIONS FROM PHOTOINITIATED BULB REACTIONS CHEMICAL PHYSICS LETTERS SHAFER, N. E., ORREWING, A. J., Simpson, W. R., Xu, H., Zare, R. N. 1993; 212 (1-2): 155-162

    View details for Web of Science ID A1993LV62900027

  • REACTION-PRODUCT IMAGING - THE H+D2 REACTION SCIENCE Kitsopoulos, T. N., Buntine, M. A., Baldwin, D. P., Zare, R. N., Chandler, D. W. 1993; 260 (5114): 1605-1610

    Abstract

    The differential cross section for the H + D(2) --> HD + D reaction has been measured using a technique called reaction product imaging. In this experiment, a photolytically produced beam of hydrogen (H) atoms crossed a beam of cold deuterium (D(2)) molecules. Product D atoms were ionized at the intersection of the two particle beams and accelerated toward a position-sensitive detector. The ion images appearing on the detector are two-dimensional projections of the three-dimensional velocity distribution of the D atom products. The reaction was studied at nominal center-of-mass collision energies of 0.54 and 1.29 electron volts. At the lower collision energy, the measured differential cross section for D atom production, summed over all final states of the HD(v,J) product, is in good agreement with recent quasi-classical trajectory calculations. At the higher collision energy, the agreement between the theoretical predictions and experimental results is less favorable.

    View details for Web of Science ID A1993LG17600018

    View details for PubMedID 17810201

  • THE INTERACTION OF CO WITH NI(111) - RAINBOWS AND ROTATIONAL TRAPPING JOURNAL OF CHEMICAL PHYSICS Hines, M. A., Zare, R. N. 1993; 98 (11): 9134-9147

    View details for Web of Science ID A1993LE41200085

  • EFFECT OF ROTATION ON THE TRANSLATIONAL AND VIBRATIONAL-ENERGY DEPENDENCE OF THE DISSOCIATIVE ADSORPTION OF D(2) ON CU(111) JOURNAL OF CHEMICAL PHYSICS Michelsen, H. A., Rettner, C. T., Auerbach, D. J., Zare, R. N. 1993; 98 (10): 8294-8307

    View details for Web of Science ID A1993LC87000067

  • DEGENERATE 4-WAVE-MIXING DIAGNOSTICS OF ATMOSPHERIC-PRESSURE DIAMOND DEPOSITION 3RD INTERNATIONAL CONF ON THE NEW DIAMOND SCIENCE AND TECHNOLOGY ( ICNDST-3 ) / 3RD EUROPEAN CONF ON DIAMOND, DIAMOND-LIKE AND RELATED COATINGS ( DF 92 ) Owano, T. G., Kruger, C. H., Green, D. S., Williams, S., Zare, R. N. ELSEVIER SCIENCE SA. 1993: 661–66

    View details for Web of Science ID A1993LE79300010

  • BOUNDARY-LAYER PROFILES IN PLASMA CHEMICAL VAPOR-DEPOSITION SCIENCE Green, D. S., Owano, T. G., Williams, S., Goodwin, D. G., Zare, R. N., Kruger, C. H. 1993; 259 (5102): 1726-1729

    Abstract

    A nonlinear optical spectroscopy based on degenerate four-wave mixing has made possible direct measurements of species temperature and concentration profiles through the boundary layer of a reactive plasma at atmospheric pressure. Spectra were obtained for CH and C(2) radicals over a range of conditions including those for the plasma chemical vapor deposition of diamond films. Numerical simulations based on a one-dimensional stagnation-point flow model are in good agreement with the measurements. The CH mole fraction is shown to rise and fall as a function of distance from the substrate, which is compelling experimental evidence for the complex chemistry that is occurring in the plasma boundary layer.

    View details for Web of Science ID A1993KT81000029

    View details for PubMedID 17816890

  • INTEGRAL RATE-CONSTANT MEASUREMENTS OF THE REACTION H+D2O-]HD(V',J')+OD JOURNAL OF CHEMICAL PHYSICS ADELMAN, D. E., Filseth, S. V., Zare, R. N. 1993; 98 (6): 4636-4643

    View details for Web of Science ID A1993KU22200031

  • EFFECT OF REAGENT VIBRATION ON THE H+HOD REACTION - AN EXAMPLE OF BOND-SPECIFIC CHEMISTRY JOURNAL OF PHYSICAL CHEMISTRY Bronikowski, M. J., Simpson, W. R., Zare, R. N. 1993; 97 (10): 2194-2203

    View details for Web of Science ID A1993KT15500021

  • COMPARISON OF REAGENT STRETCH VS BEND EXCITATION IN THE H+D2O REACTION - AN EXAMPLE OF MODE-SELECTIVE CHEMISTRY JOURNAL OF PHYSICAL CHEMISTRY Bronikowski, M. J., Simpson, W. R., Zare, R. N. 1993; 97 (10): 2204-2208

    View details for Web of Science ID A1993KT15500022

  • INTEGRAL RATE-CONSTANT MEASUREMENTS OF THE REACTION H+D2-]HD(UPSILON'=1,J')+D AT HIGH COLLISION ENERGIES CHEMICAL PHYSICS LETTERS ADELMAN, D. E., Xu, H., Zare, R. N. 1993; 203 (5-6): 573-577

    View details for Web of Science ID A1993KP24600023

  • SURFACE INDUCED DISSOCIATION FOR TANDEM TIME-OF-FLIGHT MASS-SPECTROMETRY INTERNATIONAL JOURNAL OF MASS SPECTROMETRY AND ION PROCESSES Williams, E. R., Fang, L. L., Zare, R. N. 1993; 123 (3): 233-241

    View details for Web of Science ID A1993KT46200008

  • OBSERVATION OF FLOW PROFILES IN ELECTROOSMOSIS IN A RECTANGULAR CAPILLARY JOURNAL OF CHROMATOGRAPHY Tsuda, T., Ikedo, M., Jones, G., Dadoo, R., Zare, R. N. 1993; 632 (1-2): 201-207

    View details for Web of Science ID A1993KN83400027

  • DETERMINATION OF CARBOHYDRATES BY CAPILLARY ZONE ELECTROPHORESIS WITH AMPEROMETRIC DETECTION AT A COPPER MICROELECTRODE ANALYTICAL CHEMISTRY Colon, L. A., Dadoo, R., Zare, R. N. 1993; 65 (4): 476-481

    View details for Web of Science ID A1993KL85900027

  • Photoionization Dynamics of the NO A2Σ State Deduced from Energy- and Angle-Resolved Photoelectron Spectroscopy J. Chem. Phys. Park, H., Zare, R. N. 1993; 99: 6537-6544
  • State-to-State Dynamics and Doubly Differential Cross Sections of the Reaction of Chlorine Atoms with CH4 (v3=1,J) SPIE Conf. Simpson, W. R., Orr-Ewing, A. J., Zare, R. N. 1993: 476–87
  • On the Quasiclassical Calculation of Fundamental and Overtone Intensities J. Chem. Phys. Nikitin, E. E., Noda, C., Zare, R. N. 1993; 98: 47-59
  • Flow Profile of Electroosmosis J. Chromatog. Tsuda, E., Ikedo, M., Jones, G., Dadoo, R., Zare, R. N. 1993; 632: 201-207
  • ON THE QUASI-CLASSICAL CALCULATION OF FUNDAMENTAL AND OVERTONE INTENSITIES JOURNAL OF CHEMICAL PHYSICS NIKITIN, E. E., Noda, C., Zare, R. N. 1993; 98 (1): 46-59

    View details for Web of Science ID A1993KF40600007

  • Watching Molecules Dance and Teaching Them New Steps Jahrbuch der Göttinger Akademie der Wissenschaften Zare, R. N. 1993
  • Measurement of Polycyclic Aromatic Hydrocarbon (PAHs) in Interplanetary Dust Particles Lunar Planet Sci. Conf. XXIV Clemett, S. J., Maechling, C. R., Zare, R. N., Swan, P. D., Walker, R. M. 1993
  • MEASUREMENT OF RELATIVE STATE-TO-STATE RATE CONSTANTS FOR THE REACTION D+H2(V,J)-]HD(V',J')+H JOURNAL OF CHEMICAL PHYSICS ADELMAN, D. E., SHAFER, N. E., Kliner, D. A., Zare, R. N. 1992; 97 (10): 7323-7341

    View details for Web of Science ID A1992JY56700029

  • PRODUCT ROTATIONAL DISTRIBUTIONS AND SPECIFIC OPACITY FUNCTIONS FOR THE REACTION BA +HL -] BAL (V=0,4,8,12,16,18) +H JOURNAL OF CHEMICAL PHYSICS Tsekouras, A. A., Leach, C. A., Kalogerakis, K. S., Zare, R. N. 1992; 97 (10): 7220-7225

    View details for Web of Science ID A1992JY56700018

  • DETECTION OF TRACE SPECIES IN HOSTILE ENVIRONMENTS USING DEGENERATE 4-WAVE-MIXING - CH IN AN ATMOSPHERIC-PRESSURE FLAME JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Williams, S., Green, D. S., Sethuraman, S., Zare, R. N. 1992; 114 (23): 9122-9130

    View details for Web of Science ID A1992JW79700053

  • QUASI-CLASSICAL TRAJECTORY SIMULATION OF THE KINEMATICALLY CONSTRAINED REACTION BA+HL-]BAL+H JOURNAL OF CHEMICAL PHYSICS Zhao, D. Q., Zare, R. N. 1992; 97 (9): 6208-6214

    View details for Web of Science ID A1992JX29500027

  • MEASUREMENT OF CIRCULAR-DICHROISM IN ROTATIONALLY RESOLVED PHOTOELECTRON ANGULAR-DISTRIBUTIONS FOLLOWING THE PHOTOIONIZATION OF NO A2-SIGMA+ JOURNAL OF CHEMICAL PHYSICS Leahy, D. J., Reid, K. L., Park, H. K., Zare, R. N. 1992; 97 (7): 4948-4957

    View details for Web of Science ID A1992JR33800037

  • ROTATIONAL LINE STRENGTHS FOR THE PHOTOIONIZATION OF DIATOMIC-MOLECULES JOURNAL OF CHEMICAL PHYSICS Xie, J. C., Zare, R. N. 1992; 97 (5): 2891-2899

    View details for Web of Science ID A1992JL37200006

  • INTERNAL-STATE DISTRIBUTIONS OF H-2 DESORBED FROM MONOHYDRIDE AND DIHYDRIDE SPECIES ON SI(100) JOURNAL OF CHEMICAL PHYSICS SHANE, S. F., Kolasinski, K. W., Zare, R. N. 1992; 97 (5): 3704-3709

    View details for Web of Science ID A1992JL37200090

  • ANALYSIS OF FREE INTRACELLULAR NUCLEOTIDES USING HIGH-PERFORMANCE CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY Ng, M., Blaschke, T. F., Arias, A. A., Zare, R. N. 1992; 64 (15): 1682-1684

    Abstract

    High-performance capillary electrophoresis (HPCE) with UV absorbance detection (254 nm) has been applied for analyzing intracellular free ribonucleotides. The nucleotide profiles obtained from peripheral blood lymphocytes differ from those obtained from Molt4 human leukemic cells. With a 140 mM borate buffer, pH 9.4, a nearly complete profile can be obtained in 25 min. HPCE has comparable resolution to that of high-performance liquid chromatography (HPLC) but is faster in terms of time per sample run (25 min vs 45 min) and requires much less sample (nanoliter range for HPCE vs microliter range for HPLC).

    View details for Web of Science ID A1992JF82700011

    View details for PubMedID 1443617

  • STATE-TO-STATE RATES FOR THE D+H2(V=1,J=1)-]HD(V',J')+H REACTION - PREDICTIONS AND MEASUREMENTS SCIENCE Neuhauser, D., Judson, R. S., Kouri, D. J., ADELMAN, D. E., SHAFER, N. E., Kliner, D. A., Zare, R. N. 1992; 257 (5069): 519-522

    Abstract

    A fully quantal wavepacket approach to reactive scattering in which the best available H(3) potential energy surface was used enabled a comparison with experimentally determined rates for the D + H(2)(v = 1, j = 1) --> HD(v' = 0, 1, 2; j') + H reaction at significantly higher total energies (1.4 to 2.25 electron volts) than previously possible. The theoretical results are obtained over a sufficient range of conditions that a detailed simulation of the experiment was possible, thus making this a definitive comparison of experiment and theory. Good to excellent agreement is found for the vibrational branching ratios and for the rotational distributions within each product vibrational level. However, the calculated rotational distributions are slightly hotter than the experimentally measured ones. This small discrepancy is more marked for products for which a larger fraction of the total energy appears in translation. The most likely explanation for this behavior is that refinements are needed in the potential energy surface.

    View details for Web of Science ID A1992JE75500024

    View details for PubMedID 17778685

  • RECOMBINATIVE DESORPTION OF H-2 ON SI(100)-(2X1) AND SI(111)-(7X7) - COMPARISON OF INTERNAL STATE DISTRIBUTIONS JOURNAL OF CHEMICAL PHYSICS SHANE, S. F., Kolasinski, K. W., Zare, R. N. 1992; 97 (2): 1520-1530

    View details for Web of Science ID A1992JM25300082

  • STATE-SPECIFIC STUDY OF HYDROGEN DESORPTION FROM SI(100)-(2X1) - COMPARISON OF DISILANE AND HYDROGEN ADSORPTION 38TH NATIONAL SYMP OF THE AMERICAN VACUUM SOC SHANE, S. F., Kolasinski, K. W., Zare, R. N. A V S AMER INST PHYSICS. 1992: 2287–91

    View details for Web of Science ID A1992JE68300025

  • ORGANIC-COMPOUNDS IN THE FOREST VALE, H4 ORDINARY CHONDRITE GEOCHIMICA ET COSMOCHIMICA ACTA Zenobi, R., Philippoz, J. M., Zare, R. N., Wing, M. R., Bada, J. L., Marti, K. 1992; 56 (7): 2899-2905

    Abstract

    We have analyzed the H4 ordinary chondrite Forest Vale for polycyclic aromatic hydrocarbons (PAHs) using two-step laser mass spectrometry (L2MS) and for amino acids using a standard chromatographic method. Indigenous PAHs were identified in the matrices of freshly cleaved interior faces but could not be detected in pulverized silicates and chondrules. No depth dependence of the PAHs was found in a chipped interior piece. Amino acids, taken from the entire sample, consisted of protein amino acids that were nonracemic, indicating that they are terrestrial contaminants. The presence of indigenous PAHs and absence of indigenous amino acids provides support for the contention that different processes and environments contributed to the synthesis of the organic matter in the solar system.

    View details for Web of Science ID A1992JD83900022

    View details for PubMedID 11537804

  • POLARIZATION DEPENDENCE OF THE AC STARK-EFFECT IN MULTIPHOTON TRANSITIONS OF DIATOMIC-MOLECULES JOURNAL OF CHEMICAL PHYSICS Girard, B., Sitz, G. O., Zare, R. N., BILLY, N., VIGUE, J. 1992; 97 (1): 26-41

    View details for Web of Science ID A1992JA79200005

  • COMPLETE DESCRIPTION OF MOLECULAR PHOTOIONIZATION FROM CIRCULAR-DICHROISM OF ROTATIONALLY RESOLVED PHOTOELECTRON ANGULAR-DISTRIBUTIONS PHYSICAL REVIEW LETTERS Reid, K. L., Leahy, D. J., Zare, R. N. 1992; 68 (24): 3527-3530

    View details for Web of Science ID A1992HY94300011

  • ROTATIONAL ANALYSIS OF THE BAL C2-PI-X2-SIGMA+ BAND SYSTEM FOR THE DELTA-UPSILON=0 PROGRESSION (UPSILON-LESS-THAN-OR-EQUAL-TO-12) JOURNAL OF MOLECULAR SPECTROSCOPY Leach, C. A., Tsekouras, A. A., Zare, R. N. 1992; 153 (1-2): 59-72

    View details for Web of Science ID A1992HT47800006

  • ION PICKUP OF LARGE, SURFACE-ADSORBED MOLECULES - A DEMONSTRATION OF THE ELEY-RIDEAL MECHANISM JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Williams, E. R., Jones, G. C., Fang, L., Zare, R. N., Garrison, B. J., Brenner, D. W. 1992; 114 (9): 3207-3210

    View details for Web of Science ID A1992HQ81400006

  • ROTATIONAL EFFECTS ON THE OVERTONE-INDUCED ISOMERIZATION RATE FOR CHD2NC-]CHD2CN JOURNAL OF PHYSICAL CHEMISTRY Gutow, J. H., Zare, R. N. 1992; 96 (6): 2534-2543

    View details for Web of Science ID A1992HK71700027

  • MICROSCOPIC ORGANIC-ANALYSIS USING 2-STEP LASER MASS-SPECTROMETRY - APPLICATION TO METEORITIC ACID RESIDUES ANALYTICAL CHEMISTRY Kovalenko, L. J., MAECHLING, C. R., Clemett, S. J., Philippoz, J. M., Zare, R. N., Alexander, C. M. 1992; 64 (6): 682-690

    View details for Web of Science ID A1992HJ26700021

  • DETERMINATION OF ABSOLUTE THERMAL RATE CONSTANTS FOR THE CHARGE-TRANSFER REACTION DBR+(2-PI-I,V+)+HBR-]HBR+(2-PI-I'V'+)+DBR JOURNAL OF CHEMICAL PHYSICS Xie, J. C., Zare, R. N. 1992; 96 (6): 4293-4302

    View details for Web of Science ID A1992HK01900027

  • INTERNAL-STATE DISTRIBUTION OF RECOMBINATIVE HYDROGEN DESORPTION FROM SI(100) JOURNAL OF CHEMICAL PHYSICS Kolasinski, K. W., SHANE, S. F., Zare, R. N. 1992; 96 (5): 3994-4006

    View details for Web of Science ID A1992HG95300071

  • OBSERVATION OF PERTURBATIONS IN THE ROTATIONAL MANIFOLD OF THE CN B 2-SIGMA+ UPSILON = 1 LEVEL CAUSED BY INTERACTION WITH THE CN A 2-PI-I UPSILON = 12 LEVEL JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS Black, J. F., Zare, R. N. 1992; 88 (4): 525-529

    View details for Web of Science ID A1992HG33500001

  • EXPERIMENTAL-DETERMINATION OF THE SPECIFIC OPACITY FUNCTION FOR THE BA+HI-]BAI(V=0)+H REACTION JOURNAL OF CHEMICAL PHYSICS VACCARO, P. H., Tsekouras, A. A., Zhao, D. Q., Leach, C. A., Zare, R. N. 1992; 96 (4): 2786-2798

    View details for Web of Science ID A1992HE74300037

  • CHEMILUMINESCENCE DETECTION IN CAPILLARY ELECTROPHORESIS HRC-JOURNAL OF HIGH RESOLUTION CHROMATOGRAPHY Dadoo, R., Colon, L. A., Zare, R. N. 1992; 15 (2): 133-135

    View details for Web of Science ID A1992HH03800018

  • INVESTIGATION OF THE ROLES OF VIBRATIONAL-EXCITATION AND COLLISION ENERGY IN THE ION-MOLECULE REACTION NH3+(NU-2)+ND3 CONF ON OPTICAL METHODS FOR TIME-RESOLVED AND STATE-RESOLVED CHEMISTRY Posey, L. A., GUETTLER, R. D., Zare, R. N. SPIE - INT SOC OPTICAL ENGINEERING. 1992: 431–440

    View details for Web of Science ID A1992BV62Y00045

  • LASER-DESORPTION TANDEM TIME-OF-FLIGHT MASS-SPECTROMETRY WITH CONTINUOUS LIQUID INTRODUCTION CONF ON APPLIED SPECTROSCOPY IN MATERIALS SCIENCE 2 Williams, E. R., Jones, G. C., Fang, L. L., Nagata, T., Zare, R. N. SPIE - INT SOC OPTICAL ENGINEERING. 1992: 172–181

    View details for Web of Science ID A1992BW13X00024

  • Rotational Analysis of the BaI C 2Π-X 2Σ+ Band System for the Δv=0 Progression (v≤12) J. Mol. Spectrosc. Leach, C. A., Tsekouras, A. A., Zare, R. N. 1992; 153: 59-72
  • Through a Beer Glass Darkly Parity Shafer, N. E., Zare, R. N. 1992; 7: 8-13
  • Quasiclassical Trajectory Simulation of the Kinematically Constrained Reaction Ba + HI → BaI + H J. Chem. Phys. Zhao, D., Zare, R. N. 1992; 97: 6208-6214
  • Analysis of Polycyclic Aromatic Hydrocarbons in Seventeen Ordinary and Carbonaceous Chondrites Lunar Planet Sci. Conf. XXIII Clemett, S. J., Maechling, C. R., Zare, R. N., Alexander, C. D. 1992
  • ANALYSIS OF NEUROPEPTIDES USING CAPILLARY ZONE ELECTROPHORESIS WITH MULTICHANNEL FLUORESCENCE DETECTION INTERNATIONAL CONF ON SCIENTIFIC OPTICAL IMAGING Sweedler, J. V., Shear, J. B., Fishman, H. A., Zare, R. N., Scheller, R. H. SPIE - INT SOC OPTICAL ENGINEERING. 1992: 37–46

    View details for Web of Science ID A1992BU87Q00004

  • State-to-State Rates for the D + H2 → HD + H Reaction: Predictions and Measurements Science Neuhauser, D., Judson, R. S., Kouri, D. J., Adelman, D. E., Shafer, N. E., Kliner, D. V., Zare, R. N. 1992; 257: 519-522
  • 2-STEP LASER MASS-SPECTROMETRY - ANALYSIS AT HIGH SPATIAL-RESOLUTION OF COSMOCHEMICAL SAMPLES Clemett, S. J., Kovalenko, L. J., MAECHLING, C. R., Zare, R. N. METEORITICAL SOC. 1991: 328–29

    View details for Web of Science ID A1991HF77900052

  • BOND-SPECIFIC CHEMISTRY - OD-OH PRODUCT RATIOS FOR THE REACTIONS H+HOD(100) AND H+HOD(001) JOURNAL OF CHEMICAL PHYSICS Bronikowski, M. J., Simpson, W. R., Girard, B., Zare, R. N. 1991; 95 (11): 8647-8648

    View details for Web of Science ID A1991GR66500091

  • FINE-STRUCTURE POPULATION-DISTRIBUTIONS OF O(3PJ) IN THE H + O2 REACTION AND THE PHOTOLYSIS OF NO2 CHEMICAL PHYSICS LETTERS Rubahn, H. G., vanderZande, W. J., Zhang, R., Bronikowski, M. J., Zare, R. N. 1991; 186 (2-3): 154-160

    View details for Web of Science ID A1991GR25400006

  • SURFACE-TEMPERATURE MEASUREMENT OF DIELECTRIC MATERIALS HEATED BY PULSED LASER-RADIATION - REPLY CHEMICAL PHYSICS LETTERS Zenobi, R., Hahn, J. H., Zare, R. N. 1991; 186 (1): 123-124

    View details for Web of Science ID A1991GP94200022

  • SURFACE-TEMPERATURE MEASUREMENT OF DIELECTRIC MATERIALS HEATED BY PULSED LASER-RADIATION - COMMENT CHEMICAL PHYSICS LETTERS Bauer, S., Ploss, B., Schwer, S. 1991; 186 (1): 119-122

    View details for Web of Science ID A1991GP94200021

  • SPLIT INJECTOR FOR CAPILLARY ZONE ELECTROPHORESIS 3RD INTERNATIONAL SYMP ON HIGH PERFORMANCE CAPILLARY ELECTROPHORESIS ( HPCE 91 ) Tsuda, T., Zare, R. N. ELSEVIER SCIENCE BV. 1991: 103–10

    View details for Web of Science ID A1991GP17100009

  • DETERMINATION OF MOLECULAR SYMMETRY AXIS (Z) ORIENTATION VIA PHOTOELECTRON ANGULAR-DISTRIBUTION MEASUREMENTS JOURNAL OF PHYSICAL CHEMISTRY Leahy, D. J., Reid, K. L., Zare, R. N. 1991; 95 (21): 8154-8158

    View details for Web of Science ID A1991GL63800028

  • SUPERTHERMAL WIDTHS OF THE COLLISION ENERGY-DISTRIBUTIONS IN HOT ATOM REACTIONS JOURNAL OF PHYSICAL CHEMISTRY vanderZande, W. J., Zhang, R., Zare, R. N., McKendrick, K. G., Valentini, J. J. 1991; 95 (21): 8205-8207

    View details for Web of Science ID A1991GL63800038

  • PHOTOACOUSTIC MEASUREMENT OF ABSOLUTE OVERTONE CROSS-SECTIONS CHEMICAL PHYSICS LETTERS Gutow, J. H., Davidsson, J., Zare, R. N. 1991; 185 (1-2): 120-124

    View details for Web of Science ID A1991GM15500022

  • THROUGH A BEER GLASS DARKLY PHYSICS TODAY SHAFER, N. E., Zare, R. N. 1991; 44 (10): 48-52

    View details for Web of Science ID A1991GK44200012

  • PROBING THE DYNAMICS OF HYDROGEN RECOMBINATION ON SI(100) JOURNAL OF CHEMICAL PHYSICS Kolasinski, K. W., SHANE, S. F., Zare, R. N. 1991; 95 (7): 5482-5485

    View details for Web of Science ID A1991GH35600087

  • IMPROVED END-COLUMN CONDUCTIVITY DETECTOR FOR CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Huang, X. H., Zare, R. N. 1991; 63 (19): 2193-2196

    View details for Web of Science ID A1991GG86100024

  • COMPARISON OF EXPERIMENTAL AND THEORETICAL INTEGRAL CROSS-SECTIONS FOR D+H2(V=1,J=1)-]HD(V'=1,J')+H JOURNAL OF CHEMICAL PHYSICS Kliner, D. A., ADELMAN, D. E., Zare, R. N. 1991; 95 (3): 1648-1662

    View details for Web of Science ID A1991GA10600023

  • PRODUCT INTERNAL-STATE DISTRIBUTION FOR THE REACTION H+HI-]H2+I JOURNAL OF CHEMICAL PHYSICS Kliner, D. A., RINNEN, K. D., Buntine, M. A., ADELMAN, D. E., Zare, R. N. 1991; 95 (3): 1663-1670

    View details for Web of Science ID A1991GA10600024

  • EFFECT OF BREAKING CYLINDRICAL SYMMETRY ON PHOTOELECTRON ANGULAR-DISTRIBUTIONS RESULTING FROM RESONANCE-ENHANCED 2-PHOTON IONIZATION JOURNAL OF CHEMICAL PHYSICS Reid, K. L., Leahy, D. J., Zare, R. N. 1991; 95 (3): 1746-1756

    View details for Web of Science ID A1991GA10600032

  • COMPLETE DESCRIPTION OF 2-PHOTON(1+1') IONIZATION OF NO DEDUCED FROM ROTATIONALLY RESOLVED PHOTOELECTRON ANGULAR-DISTRIBUTIONS JOURNAL OF CHEMICAL PHYSICS Leahy, D. J., Reid, K. L., Zare, R. N. 1991; 95 (3): 1757-1767

    View details for Web of Science ID A1991GA10600033

  • ANALYSIS OF BAI C2-PI-X2-SIGMA+ (0, 0) BAND FOR HIGH ROTATIONAL LEVELS JOURNAL OF MOLECULAR SPECTROSCOPY Zhao, D., VACCARO, P. H., Tsekouras, A. A., Leach, C. A., Zare, R. N. 1991; 148 (1): 226-242

    View details for Web of Science ID A1991FR89500021

  • QUANTITATIVE-DETERMINATION OF H2, HD, AND D2 INTERNAL-STATE DISTRIBUTIONS BY (2+1) RESONANCE-ENHANCED MULTIPHOTON IONIZATION JOURNAL OF CHEMICAL PHYSICS RINNEN, K. D., Buntine, M. A., Kliner, D. A., Zare, R. N., Huo, W. M. 1991; 95 (1): 214-225

    View details for Web of Science ID A1991FT84700023

  • ROTATIONAL AND VIBRATIONAL EFFECTS IN THE E 1-SIGMA-G+-X 1-SIGMA-G+ 2-PHOTON TRANSITIONS OF H2, HD, AND D2 JOURNAL OF CHEMICAL PHYSICS Huo, W. M., RINNEN, K. D., Zare, R. N. 1991; 95 (1): 205-213

    View details for Web of Science ID A1991FT84700022

  • ORGANIC-CHEMICAL ANALYSIS ON A MICROSCOPIC SCALE USING 2-STEP LASER DESORPTION LASER IONIZATION MASS-SPECTROMETRY SPACE SCIENCE REVIEWS Kovalenko, L. J., Philippoz, J. M., BUCENELL, J. R., Zenobi, R., Zare, R. N. 1991; 56 (1-2): 191-195

    View details for Web of Science ID A1991FA72700027

  • ROTATIONAL ANALYSIS OF THE BAL C2-PI-X2-SIGMA+ (8,8) BAND JOURNAL OF MOLECULAR SPECTROSCOPY Leach, C. A., WALDECK, J. R., Noda, C., MCKILLOP, J. S., Zare, R. N. 1991; 146 (2): 465-492

    View details for Web of Science ID A1991FD46600019

  • APPLICATION OF ION IMAGING TO THE ATOM-MOLECULE EXCHANGE-REACTION - H+HI-]H2+I JOURNAL OF CHEMICAL PHYSICS Buntine, M. A., Baldwin, D. P., Zare, R. N., Chandler, D. W. 1991; 94 (6): 4672-4675

    View details for Web of Science ID A1991FD73500064

  • FLUORESCENCE DETECTION IN CAPILLARY ZONE ELECTROPHORESIS USING A CHARGE-COUPLED DEVICE WITH TIME-DELAYED INTEGRATION ANALYTICAL CHEMISTRY Sweedler, J. V., Shear, J. B., Fishman, H. A., Zare, R. N., Scheller, R. H. 1991; 63 (5): 496-502

    Abstract

    A fluorescence detection system for capillary zone electrophoresis is described in which a charged-coupled device (CCD) views a 2-cm section of an axially illuminated capillary column. The CCD is operated in two readout modes: a snapshot mode that acquires a series of images in wavelength and capillary position, and a time-delayed integration mode that allows long exposure times of the moving analyte zones. By use of the latter mode, the ability to differentiate a species based on both its fluorescence emission and migration rate is demonstrated for fluorescein and sulforhodamine 101. The detection limit for fluorescein isothiocyanate (FITC) is 1.2 X 10(-20) mol; detection limits for FITC-amino acids are in the (2-8) X 10(-20) mol range.

    View details for Web of Science ID A1991FA18800024

    View details for PubMedID 1905883

  • EFFECT OF REAGENT ROTATION ON PRODUCT ENERGY DISPOSAL IN THE LIGHT ATOM TRANSFER-REACTION O(3P)+HCL(V = 2,J = 1,6,9)-]OH(V',N')+CL(2P) JOURNAL OF CHEMICAL PHYSICS Zhang, R., vanderZande, W. J., Bronikowski, M. J., Zare, R. N. 1991; 94 (4): 2704-2712

    View details for Web of Science ID A1991EY07000039

  • FERMI RESONANCE IN THE OVERTONE SPECTRA OF THE CH CHROMOPHORE IN CHBR3 .2. VISIBLE SPECTRA JOURNAL OF PHYSICAL CHEMISTRY Davidsson, J., Gutow, J. H., Zare, R. N., HOLLENSTEIN, H. A., Marquardt, R. R., QUACK, M. 1991; 95 (3): 1201-1209

    View details for Web of Science ID A1991EW47800031

  • DIRECT VISUALIZATION OF BRAGG-DIFFRACTION WITH A HE-NE-LASER AND AN ORDERED SUSPENSION OF CHARGED MICROSPHERES JOURNAL OF CHEMICAL EDUCATION SPENCER, B. H., Zare, R. N. 1991; 68 (2): 97-100

    View details for Web of Science ID A1991EY74600007

  • END-COLUMN DETECTION FOR CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Huang, X. H., Zare, R. N., Sloss, S., Ewing, A. G. 1991; 63 (2): 189-192

    View details for Web of Science ID A1991ER43200020

    View details for PubMedID 1812795

  • THE H+PARA-H2 REACTION - INFLUENCE OF DYNAMIC RESONANCES ON H-2 (V'=1,J'=1 AND 3) INTEGRAL CROSS-SECTIONS JOURNAL OF CHEMICAL PHYSICS Kliner, D. A., ADELMAN, D. E., Zare, R. N. 1991; 94 (2): 1069-1080

    View details for Web of Science ID A1991EU59200027

  • Rotational Analysis of the BaI C 2Π - X 2Σ+ (8,8) Band J. Mol. Spectrosc. Leach, C. A., Waldeck, J. R., Noda, C., McKillop, J. S., Zare, R. N. 1991; 146: 465-492
  • Surface Temperature Measurement of Dielectric Materials Heated by Pulsed Laser Radiation Physical chemistry letters Zenobi, R., Hahn, J. H., Zare, R. N. 1991; 186: 119-122
  • PROTOCOL FOR RESOLVING PROTEIN MIXTURES IN CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Gordon, M. J., Lee, K. J., Arias, A. A., Zare, R. N. 1991; 63 (1): 69-72

    Abstract

    The separation of protein mixtures by capillary zone electrophoresis can be plagued by wall adsorption of the protein components, causing peak broadening and distortion. A method is presented for overcoming this problem by adding ethylene glycol to the protein sample and by choosing the running buffer and protein sample to be at different pH values and molarities. This protocol appears to work for a wide class of proteins having different molecular weights and pI values. The method has been applied to the analysis of proteins in human serum. Compared to the traditional method of agarose gel electrophoresis, the present method is more rapid and offers better resolution, suggesting its potential as a clinical diagnostic of certain disease states.

    View details for Web of Science ID A1991EP72100016

    View details for PubMedID 1810169

  • Two-Step Laser Mass Spectrometry Advances in Multi-Photon Processes and Spectroscopy Zenobi, R., Zare, R. N. edited by Lin, S. H. World Scientific Publishing. 1991: 1–167
  • EFFECT OF BREAKING CYLINDRICAL SYMMETRY ON PHOTOELECTRON ANGULAR-DISTRIBUTIONS RESULTING FROM RESONANCE-ENHANCED 2-PHOTON IONIZATION INSTITUTE OF PHYSICS CONFERENCE SERIES Reid, K. L., Leahy, D. J., ALLENDORF, S. W., Zare, R. N. 1991: 345-350

    View details for Web of Science ID A1991FW89900082

  • Protocol for Resolving Protein Mixtures in Capillary Zone Electrophoresis Anal. Chem. Gordon, M. J., Lee, K. J., Arias, A. A., Zare, R. N. 1991; 63: 69-72
  • The H + para-H2 Reaction: Influence of Dynamical Resonances on H2(v'=1, j'=1 and 3) Integral Cross Sections J. Chem. Phys. Kliner, D. V., Adelman, D. E., Zare, R. N. 1991; 94: 1069-1080
  • Improved End-Column Detector for Capillary Zone Electrophoresis Anal. Chem. Huang, X., Zare, R. N. 1991; 63: 2193-2196
  • Erratum: Hyperfine Structure of the BaI X 2Σ+ and C 2Π States J. Chem. Phys. Leach, C. A., Ernst, W. E., Kändler, J., Noda, C., McKillop, J. S., Zare, R. N. 1991; 95 (9433)
  • INDIRECT INFORMATION ON REACTIVE TRANSITION-STATES FROM CONSERVATION OF ANGULAR-MOMENTUM FARADAY DISCUSSIONS Leach, C. A., Tsekouras, A. A., VACCARO, P. H., Zare, R. N., Zhao, D. Q. 1991; 91: 183-190

    View details for Web of Science ID A1991GY59700014

  • Surface Temperature Measurement of Dielectric Materials Heated by Pulsed Laser Radiation Chemical Physics Letters Zenobi, R., Hahn, J. H., Zare, R. N. 1991; 186: 119-122
  • Quantitative Determination of H2, HD, and D2 Internal-State Distributions by (2+1) REMPI J. Chem. Phys. Rinnen, K. D., Buntine, M. A., Kliner, D. V., Zare, R. N., Huo, W. M. 1991; 95: 214-225
  • LASER SPECTROSCOPY OF CROSSED MOLECULAR-BEAMS - THE DISSOCIATION-ENERGY OF BAL FROM ENERGY-BALANCE MEASUREMENTS JOURNAL OF CHEMICAL PHYSICS VACCARO, P. H., Zhao, D., Tsekouras, A. A., Leach, C. A., Ernst, W. E., Zare, R. N. 1990; 93 (12): 8544-8556

    View details for Web of Science ID A1990EP16000015

  • 2+1 RESONANTLY ENHANCED MULTIPHOTON IONIZATION OF CO VIA THE E1-PI-X1-SIGMA+ TRANSITION - FROM MEASURED ION SIGNALS TO QUANTITATIVE POPULATION-DISTRIBUTIONS JOURNAL OF CHEMICAL PHYSICS Hines, M. A., Michelsen, H. A., Zare, R. N. 1990; 93 (12): 8557-8564

    View details for Web of Science ID A1990EP16000016

  • PHOTOFRAGMENT ORIENTATION AS A PROBE OF NEAR-THRESHOLD NONADIABATIC PHENOMENA IN THE PHOTODISSOCIATION OF ICN MOLECULAR PHYSICS Black, J. F., Hasselbrink, E., WALDECK, J. R., Zare, R. N. 1990; 71 (5): 1143-1153

    View details for Web of Science ID A1990ET64300016

  • QUANTITATION OF RIBONUCLEOTIDES FROM BASE-HYDROLYZED RNA USING CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Huang, X. H., Shear, J. B., Zare, R. N. 1990; 62 (18): 2049-2051

    View details for Web of Science ID A1990DZ20900029

    View details for PubMedID 1700643

  • FRAGMENT ISOTOPE DISTRIBUTION AS A SIGNATURE OF MOLECULAR FLUXIONALITY CHEMICAL PHYSICS LETTERS Brauman, J. I., Zare, R. N., Levine, R. D. 1990; 172 (3-4): 231-234

    View details for Web of Science ID A1990DZ50500008

  • CONTINUOUS SAMPLE COLLECTION IN CAPILLARY ZONE ELECTROPHORESIS BY COUPLING THE OUTLET OF A CAPILLARY TO A MOVING SURFACE 2ND INTERNATIONAL SYMP ON HIGH PERFORMANCE CAPILLARY ELECTROPHORESIS ( HPCE 90 ) Huang, X. H., Zare, R. N. ELSEVIER SCIENCE BV. 1990: 185–89

    Abstract

    Use of an on-column frit structure, constructed by sintering a mixture of glass powders, makes it possible to ground a fused-silica capillary on its side prior to its outlet. Electroosmotic pressure permits convenient sample collection. We illustrate the use of this device by depositing the eluent in a continuous manner on a moving surface. This provides a permanent record of the separated species in a mixture.

    View details for Web of Science ID A1990EA11800019

    View details for PubMedID 2286622

  • SELECTION-RULES FOR THE PHOTOIONIZATION OF DIATOMIC-MOLECULES JOURNAL OF CHEMICAL PHYSICS Xie, J. C., Zare, R. N. 1990; 93 (5): 3033-3038

    View details for Web of Science ID A1990DW34200006

  • FLUORESCENCE POLARIZATION OF A DIATOMIC FRAGMENT FOLLOWING PHOTODISSOCIATION OF A TRIATOMIC PRECURSOR MOLECULAR PHYSICS Nagata, T., Kondow, T., Zare, R. N. 1990; 70 (6): 1159-1162

    View details for Web of Science ID A1990EA40200016

  • NATURE OF THE RED EMISSION IN THE CHEMICAL OXYGEN IODINE LASER SYSTEM CHEMICAL PHYSICS LETTERS Huang, R., Zhang, R., Zare, R. N. 1990; 170 (5-6): 437-440

    View details for Web of Science ID A1990DR90600005

  • DETECTION OF CONCEALED EXPLOSIVES SCIENCE Williams, E. R., Zare, R. N. 1990; 248 (4962): 1471-1472

    View details for Web of Science ID A1990DK40800004

  • EFFECT OF INDISTINGUISHABLE NUCLEI ON PRODUCT ROTATIONAL DISTRIBUTIONS - D+DI-]D2+I CHEMICAL PHYSICS LETTERS RINNEN, K. D., Kliner, D. A., Buntine, M. A., Zare, R. N. 1990; 169 (5): 365-371

    View details for Web of Science ID A1990DL47800001

  • EXPERIMENTAL IMPROVEMENTS IN RECORDING GAS-PHASE PHOTOACOUSTIC SPECTRA JOURNAL OF PHYSICAL CHEMISTRY Davidsson, J., Gutow, J. H., Zare, R. N. 1990; 94 (10): 4069-4073

    View details for Web of Science ID A1990DE69600035

  • EVIDENCE FOR 3 INTERACTING POTENTIAL-ENERGY SURFACES IN THE PHOTODISSOCIATION OF ICN AT 249 NM JOURNAL OF CHEMICAL PHYSICS Black, J. F., WALDECK, J. R., Zare, R. N. 1990; 92 (6): 3519-3538

    View details for Web of Science ID A1990CU65800026

  • USE OF AN ON-COLUMN FRIT IN CAPILLARY ZONE ELECTROPHORESIS - SAMPLE COLLECTION ANALYTICAL CHEMISTRY Huang, X. H., Zare, R. N. 1990; 62 (5): 443-446

    View details for Web of Science ID A1990CQ35000008

  • THE D+H2 REACTION - COMPARISON OF EXPERIMENT WITH QUANTUM-MECHANICAL AND QUASI-CLASSICAL CALCULATIONS CHEMICAL PHYSICS LETTERS Kliner, D. A., RINNEN, K. D., Zare, R. N. 1990; 166 (2): 107-111

    View details for Web of Science ID A1990CP12400001

  • SIMPLE-MODEL FOR LAMBDA-DOUBLET PROPENSITIES IN BIMOLECULAR REACTIONS CHEMICAL PHYSICS LETTERS Bronikowski, M. J., Zare, R. N. 1990; 166 (1): 5-10

    View details for Web of Science ID A1990CP12300002

  • D+H-2(V=1,J=1) - ROVIBRONIC STATE TO ROVIBRONIC STATE REACTION DYNAMICS JOURNAL OF CHEMICAL PHYSICS Kliner, D. A., Zare, R. N. 1990; 92 (3): 2107-2109

    View details for Web of Science ID A1990CM18400073

  • Collisional Energy Spread in Hot-Atom Reactions Caused by Thermal Motions of the Reagents Spectral Line Shapes van der Zande, W. J., Zhang, R., Zare, R. N. edited by Frommhold, L., Keto, J. W. 1990: 301–310
  • Possible Quantum Effects in Collisional Energy Transfer in Highly Excited Molecule Chem. Phys. Lett. Gilbert, R. G., Zare, R. N. 1990; 167: 407-411
  • Laser Photochemistry 1991 McGraw-Hill Yearbook of Science and Technology Zare, R. N. 1990: 213-214
  • The Future of Lasers in Analytical Chemistry Chromatography Zare, R. N. 1990; 11: 8-10
  • ON-COLUMN RADIOISOTOPE DETECTION FOR CAPILLARY ELECTROPHORESIS ACS SYMPOSIUM SERIES PENTONEY, S. L., Zare, R. N., Quint, J. F. 1990; 434: 60-89

    View details for Web of Science ID A1990DV38600004

  • Rectangular Capillaries for Capillary Electrophoresis Anal. Chem. Tsuda, T., Sweedler, J. V., Zare, R. N. 1990; 62: 2149-2152
  • Evidence for Three Interacting Potential Energy Surfaces in the Photodissociation of ICN at 249 nm J. Chem. Phys. Black, J. F., Waldeck, J. R., Zare, R. N. 1990; 92: 3519-3538
  • The D + H2 Reaction: Comparison of Experiment with Quantum-Mechanical and Quasiclassical Calculations Chem. Phys. Lett. Kliner, D. A., Rinnen, K. D., Zare, R. N. 1990; 166: 107-111
  • THE H+D2 REACTION - QUANTUM-STATE DISTRIBUTIONS AT COLLISION ENERGIES OF 1.3 AND 0.55EV JOURNAL OF CHEMICAL PHYSICS RINNEN, K. D., Kliner, D. A., Zare, R. N. 1989; 91 (12): 7514-7529

    View details for Web of Science ID A1989CD88000022

  • SPATIALLY RESOLVED ORGANIC-ANALYSIS OF THE ALLENDE METEORITE SCIENCE Zenobi, R., Philippoz, J. M., Buseck, P. R., Zare, R. N. 1989; 246 (4933): 1026-1029

    Abstract

    The distribution of polycyclic aromatic hydrocarbons(PAHs) in the Allende meteorite has been probed with two-step laser desorption/laser multiphoton ionization mass spectrometry. This method allows direct in situ analysis with a spatial resolution of 1 square millimeter or better of selected organic molecules. Spectra from freshly fractured interior surfaces of the meteorite show that PAH concentrations are locally high compared to the average concentrations found by wet chemical analysis of pulverized samples. The data suggest that the PAHs are primarily associated with the fine-grained matrix, where the organic polymer occurs. In addition, highly substituted PAH skeletons were observed. Interiors of individual chondrules were devoid of PAHs at our detection limit(about 0.05 parts per million).

    View details for Web of Science ID A1989CA77600038

    View details for PubMedID 17806393

  • EXPERIMENTAL-MEASUREMENT OF THE RADIATIVE LIFETIME OF NO+(X1-SIGMA+, V=1, 2 AND 3) CHEMICAL PHYSICS LETTERS Kuo, C. H., BEGGS, C. G., Kemper, P. R., BOWERS, M. T., Leahy, D. J., Zare, R. N. 1989; 163 (4-5): 291-296

    View details for Web of Science ID A1989CC24600003

  • HIGH-PERFORMANCE CAPILLARY ELECTROPHORESIS AMERICAN BIOTECHNOLOGY LABORATORY BUROLLA, V. P., PENTONEY, S. L., Zare, R. 1989; 7 (10): 20-26

    View details for Web of Science ID A1989CC21100002

  • THE HF AND DF B1SIGMA+-X1SIGMA+ AND C1II-X1SIGMA+ BAND SYSTEMS STUDIED BY 1 XUV + 1 UV RESONANCE ENHANCED MULTIPHOTON IONIZATION JOURNAL OF MOLECULAR SPECTROSCOPY TASHIRO, L. M., Ubachs, W., Zare, R. N. 1989; 138 (1): 89-101

    View details for Web of Science ID A1989AY13000011

  • DIRECT INELASTIC-SCATTERING OF N-2 FROM AG(111) .4. SCATTERING FROM HIGH-TEMPERATURE SURFACE JOURNAL OF CHEMICAL PHYSICS Kummel, A. C., Sitz, G. O., Zare, R. N., TULLY, J. C. 1989; 91 (9): 5793-5801

    View details for Web of Science ID A1989AW83600078

  • ANALYSIS OF FACTORS CAUSING PEAK BROADENING IN CAPILLARY ZONE ELECTROPHORESIS JOURNAL OF CHROMATOGRAPHY Huang, X. H., Coleman, W. F., Zare, R. N. 1989; 480: 95-110

    View details for Web of Science ID A1989CA11000007

  • SEMICONDUCTOR RADIOISOTOPE DETECTOR FOR CAPILLARY ELECTROPHORESIS JOURNAL OF CHROMATOGRAPHY PENTONEY, S. L., Zare, R. N., Quint, J. F. 1989; 480: 259-270

    View details for Web of Science ID A1989CA11000019

  • DETERMINATION OF METAL-ION COMPLEXES IN ELECTROPLATING SOLUTIONS USING CAPILLARY ZONE ELECTROPHORESIS WITH UV DETECTION JOURNAL OF CHROMATOGRAPHY Aguilar, M., Huang, X. H., Zare, R. N. 1989; 480: 427-431

    View details for Web of Science ID A1989CA11000038

  • EFFECT OF ELECTROLYTE AND SAMPLE CONCENTRATION ON THE RELATIONSHIP BETWEEN SENSITIVITY AND RESOLUTION IN CAPILLARY ZONE ELECTROPHORESIS USING CONDUCTIVITY DETECTION JOURNAL OF CHROMATOGRAPHY Huang, X. H., Gordon, M. J., Zare, R. N. 1989; 480: 285-288

    View details for Web of Science ID A1989CA11000022

  • SIMPLIFIED TRAJECTORY METHOD FOR MODELING GAS SURFACE SCATTERING - THE NO/PT(111) SYSTEM JOURNAL OF CHEMICAL PHYSICS Jacobs, D. C., Zare, R. N. 1989; 91 (5): 3196-3207

    View details for Web of Science ID A1989AM21300049

  • ROTATIONAL POPULATION AND ALIGNMENT DISTRIBUTIONS FOR INELASTIC-SCATTERING AND TRAPPING DESORPTION OF NO ON PT(111) JOURNAL OF CHEMICAL PHYSICS Jacobs, D. C., Kolasinski, K. W., SHANE, S. F., Zare, R. N. 1989; 91 (5): 3182-3195

    View details for Web of Science ID A1989AM21300048

  • HIGH-RESOLUTION ANGLE-RESOLVED AND ENERGY-RESOLVED PHOTOELECTRON-SPECTROSCOPY OF NO - PARTIAL-WAVE DECOMPOSITION OF THE IONIZATION CONTINUUM JOURNAL OF CHEMICAL PHYSICS ALLENDORF, S. W., Leahy, D. J., Jacobs, D. C., Zare, R. N. 1989; 91 (4): 2216-2234

    View details for Web of Science ID A1989AK29300031

  • ROTATIONAL ALIGNMENT OF NO FROM PT(111) - INELASTIC-SCATTERING AND MOLECULAR DESORPTION JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS II Jacobs, D. C., Kolasinski, K. W., Madix, R. J., Zare, R. N. 1989; 85: 1325-1335

    View details for Web of Science ID A1989AV92200020

  • ONLINE RADIOISOTOPE DETECTION FOR CAPILLARY ELECTROPHORESIS ANALYTICAL CHEMISTRY PENTONEY, S. L., Zare, R. N., Quint, J. F. 1989; 61 (15): 1642-1647

    View details for Web of Science ID A1989AJ11700013

  • ROTATIONALLY STATE-SELECTED HBR+ - PREPARATION AND CHARACTERIZATION CHEMICAL PHYSICS LETTERS Xie, J. C., Zare, R. N. 1989; 159 (5-6): 399-405

    View details for Web of Science ID A1989AG87500001

  • TIME EVOLUTION OF NON-PHOTOCHEMICAL HOLE BURNING LINEWIDTHS - OBSERVATION OF SPECTRAL DIFFUSION AT LONG TIMES CHEMICAL PHYSICS LETTERS Littau, K. A., Bai, Y. S., Fayer, M. D. 1989; 159 (1): 1-6

    View details for Web of Science ID A1989AF05000001

  • PULSED HEATING OF SURFACES - COMPARISON BETWEEN NUMERICAL-SIMULATION, ANALYTICAL MODELS, AND EXPERIMENTS CHEMICAL PHYSICS LETTERS Philippoz, J. M., Zenobi, R., Zare, R. N. 1989; 158 (1-2): 12-17

    View details for Web of Science ID A1989U902300003

  • ROTATIONAL-DYNAMICS OF DESORPTION AND INELASTIC-SCATTERING FOR THE NO/PT(111) SYSTEM JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Jacobs, D. C., Kolasinski, K. W., Madix, R. J., Zare, R. N. 1989; 7 (3): 1871-1877

    View details for Web of Science ID A1989U715400065

  • FERMI RESONANCE STRUCTURE IN THE CH VIBRATIONAL OVERTONES OF CD3CHO JOURNAL OF CHEMICAL PHYSICS AMREIN, A., Hollenstein, H., QUACK, M., Zenobi, R., Segall, J., Zare, R. N. 1989; 90 (8): 3944-3951

    View details for Web of Science ID A1989U110300006

  • DETERMINATION OF POPULATION, ALIGNMENT, AND ORIENTATION USING LASER-INDUCED FLUORESCENCE WITH UNRESOLVED EMISSION .2. JOURNAL OF CHEMICAL PHYSICS WALDECK, J. R., Kummel, A. C., Sitz, G. O., Zare, R. N. 1989; 90 (8): 4112-4114

    View details for Web of Science ID A1989U110300024

  • EFFECT OF INDISTINGUISHABLE NUCLEI ON PRODUCT ROTATIONAL DISTRIBUTIONS - THE H+HI-]H2+I REACTION JOURNAL OF CHEMICAL PHYSICS Kliner, D. A., RINNEN, K. D., Zare, R. N. 1989; 90 (8): 4625-4627

    View details for Web of Science ID A1989U110300083

  • CONSTRUCTION OF A SHUTTERED TIME-OF-FLIGHT MASS-SPECTROMETER FOR SELECTIVE ION DETECTION REVIEW OF SCIENTIFIC INSTRUMENTS RINNEN, K. D., Kliner, D. A., Blake, R. S., Zare, R. N. 1989; 60 (4): 717-719

    View details for Web of Science ID A1989U020500032

  • QUANTITATIVE-ANALYSIS OF LOW-MOLECULAR WEIGHT CARBOXYLIC-ACIDS BY CAPILLARY ZONE ELECTROPHORESIS CONDUCTIVITY DETECTION ANALYTICAL CHEMISTRY Huang, X. H., LUCKEY, J. A., Gordon, M. J., Zare, R. N. 1989; 61 (7): 766-770

    View details for Web of Science ID A1989T880800026

  • PHOTOFRAGMENT ANGULAR-DISTRIBUTIONS FROM ORIENTED SYMMETRIC-TOP PRECURSOR MOLECULES CHEMICAL PHYSICS LETTERS Zare, R. N. 1989; 156 (1): 1-6

    View details for Web of Science ID A1989T875100001

  • REACTION DYNAMICS OF H+O-2 AT 1.6-EV COLLISION ENERGY CHEMICAL PHYSICS LETTERS Bronikowski, M. J., Zhang, R., Rakestraw, D. J., Zare, R. N. 1989; 156 (1): 7-13

    View details for Web of Science ID A1989T875100002

  • STUDY OF THE N2B1-PI-U STATE VIA 1+1 MULTIPHOTON IONIZATION CHEMICAL PHYSICS Ubachs, W., TASHIRO, L., Zare, R. N. 1989; 130 (1-3): 1-13

    View details for Web of Science ID A1989T202600001

  • Utilization of 1+1 REMPI as a Probe of Rotational Dynamics in Gas-Surface Scattering AIP Conference Proceedings Jacobs, D. C., Kolasinski, K. W., Zare, R. N. 1989: 426–429
  • Sub-Doppler Polarisation Studies J. Chem. Soc., Faraday Trans. 2 Black, J. F., Waldeck, J. R., Zare, R. N. 1989; 85: 1312-1315
  • QUANTITATIVE-DETERMINATION OF HD INTERNAL STATE DISTRIBUTIONS VIA (2+1) REMPI ISRAEL JOURNAL OF CHEMISTRY RINNEN, K. D., Kliner, D. A., Zare, R. N., Huo, W. M. 1989; 29 (4): 369-382

    View details for Web of Science ID A1989CR09200005

  • Reaction Dynamics of H + O2 at 1.6 eV Collision Energy Chem. Phys. Lett. Bronikowski, M. J., Zhang, R., Rakestraw, D. J., Zare, R. N. 1989; 156: 7-13
  • High-Resolution Angle-and Energy-Resolved Photoelectron Spectroscopy of NO: Partial Wave Decomposition of the Ionization Continuum J. Chem. Phys. Allendorf, S. W., Leahy, D. J., Jacobs, D. C., Zare, R. N. 1989; 91: 2216-2234
  • Sub-Doppler Orientation J. Chem. Soc., Faraday Trans. 2 Black, J. F., Waldeck, J. R., Hasselbrink, E., Zare, R. N. 1989; 85: 1044-1047
  • Study of the N2 b1Πu State via 1+1 Multiphoton Ionization Chem. Phys. Ubachs, W., Tashiro, L., Zare, R. N. 1989; 130: 1-13
  • THE H+D2 REACTION - HD(UPSILON=1,J) AND HD(UPSILON=2,J) DISTRIBUTIONS AT A COLLISION ENERGY OF 1.3 EV CHEMICAL PHYSICS LETTERS Blake, R. S., RINNEN, K. D., Kliner, D. A., Zare, R. N. 1988; 153 (5): 365-370

    View details for Web of Science ID A1988R557700001

  • THE H+D2 REACTION - PROMPT HD DISTRIBUTIONS AT HIGH COLLISION ENERGIES CHEMICAL PHYSICS LETTERS RINNEN, K. D., Kliner, D. A., Blake, R. S., Zare, R. N. 1988; 153 (5): 371-375

    View details for Web of Science ID A1988R557700002

  • OVERTONE SPECTRA OF C-H OSCILLATORS IN COLD MOLECULES JOURNAL OF CHEMICAL PHYSICS Crofton, M. W., Stevens, C. G., Klenerman, D., Gutow, J. H., Zare, R. N. 1988; 89 (12): 7100-7111

    View details for Web of Science ID A1988R452000007

  • NUMERICAL COMPUTATION OF 9-J SYMBOLS MOLECULAR PHYSICS Zhao, D. Q., Zare, R. N. 1988; 65 (5): 1263-1268

    View details for Web of Science ID A1988R628300019

  • ONLINE CONNECTOR FOR MICROCOLUMNS - APPLICATION TO THE ON-COLUMN ORTHO-PHTHALDIALDEHYDE DERIVATIZATION OF AMINO-ACIDS SEPARATED BY CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY PENTONEY, S. L., Huang, X. H., Burgi, D. S., Zare, R. N. 1988; 60 (23): 2625-2629

    View details for Web of Science ID A1988R129600019

    View details for PubMedID 3239811

  • DIRECT INELASTIC-SCATTERING OF N-2 FROM AG(111) .3. NORMAL INCIDENT N-2 JOURNAL OF CHEMICAL PHYSICS Kummel, A. C., Sitz, G. O., Zare, R. N., TULLY, J. C. 1988; 89 (11): 6947-6955

    View details for Web of Science ID A1988R143800044

  • COMPARISON OF THE CA + HF(DF) AND SR + HF(DF) REACTION DYNAMICS JOURNAL OF CHEMICAL PHYSICS Zhang, R., Rakestraw, D. J., McKendrick, K. G., Zare, R. N. 1988; 89 (10): 6283-6294

    View details for Web of Science ID A1988Q804400035

  • OVERTONE-INDUCED ISOMERIZATION OF ALLYL ISOCYANIDE JOURNAL OF CHEMICAL PHYSICS Segall, J., Zare, R. N. 1988; 89 (9): 5704-5714

    View details for Web of Science ID A1988Q766600043

  • ORIENTATION OF THE CN X-2-SIGMA+ FRAGMENT FOLLOWING PHOTOLYSIS OF ICN BY CIRCULARLY POLARIZED-LIGHT CHEMICAL PHYSICS Hasselbrink, E., WALDECK, J. R., Zare, R. N. 1988; 126 (1): 191-200

    View details for Web of Science ID A1988Q526300019

  • CAPILLARY ELECTROPHORESIS SCIENCE Gordon, M. J., Huang, X. H., PENTONEY, S. L., Zare, R. N. 1988; 242 (4876): 224-228

    Abstract

    Electrophoretic separations carried out in capillary tubes offer the possibilities of rapid and automated analyses of small volumes of complex mixtures with unprecedented resolution and sensitivity. Some emerging developments of this new instrumentation are reviewed.

    View details for Web of Science ID A1988Q436800028

    View details for PubMedID 17787651

  • SURFACE-TEMPERATURE MEASUREMENT OF DIELECTRIC MATERIALS HEATED BY PULSED LASER-RADIATION CHEMICAL PHYSICS LETTERS Zenobi, R., Hahn, J. H., Zare, R. N. 1988; 150 (5): 361-365

    View details for Web of Science ID A1988Q276800001

  • DYNAMICS OF THE REACTION O(P-3) + HBR - EXPERIMENTAL INVESTIGATION AND THEORETICAL MODELING JOURNAL OF PHYSICAL CHEMISTRY McKendrick, K. G., Rakestraw, D. J., Zhang, R., Zare, R. N. 1988; 92 (19): 5530-5540

    View details for Web of Science ID A1988Q413400040

  • CURRENT-MONITORING METHOD FOR MEASURING THE ELECTROOSMOTIC FLOW-RATE IN CAPILLARY ZONE ELECTROPHORESIS ANALYTICAL CHEMISTRY Huang, X. H., Gordon, M. J., Zare, R. N. 1988; 60 (17): 1837-1838

    View details for Web of Science ID A1988P919500042

  • LASER-BASED MEASUREMENT OF REFRACTIVE-INDEX CHANGES - KINETICS OF 2,3-EPOXY-1-PROPANOL HYDROLYSIS JOURNAL OF CHEMICAL EDUCATION Spencer, B., Zare, R. N. 1988; 65 (9): 835-836

    View details for Web of Science ID A1988Q348700048

  • DIRECT INELASTIC-SCATTERING OF N2 FROM AG(111) .2. ORIENTATION JOURNAL OF CHEMICAL PHYSICS Sitz, G. O., Kummel, A. C., Zare, R. N., TULLY, J. C. 1988; 89 (4): 2572-2582

    View details for Web of Science ID A1988P638800091

  • A NOMENCLATURE FOR LAMBDA-DOUBLET LEVELS IN ROTATING LINEAR-MOLECULES JOURNAL OF CHEMICAL PHYSICS Alexander, M. H., Andresen, P., Bacis, R., Bersohn, R., Comes, F. J., Dagdigian, P. J., Dixon, R. N., Field, R. W., Flynn, G. W., Gericke, K. H., Grant, E. R., Howard, B. J., HUBER, J. R., King, D. S., KINSEY, J. L., Kleinermanns, K., KUCHITSU, K., Luntz, A. C., McCaffery, A. J., Pouilly, B., Reisler, H., Rosenwaks, S., Rothe, E. W., Shapiro, M., SIMONS, J. P., Vasudev, R., WIESENFELD, J. R., Wittig, C., Zare, R. N. 1988; 89 (4): 1749-1753

    View details for Web of Science ID A1988P638800001

  • DIRECT INELASTIC-SCATTERING OF N2 FROM AG(111) .1. ROTATIONAL POPULATIONS AND ALIGNMENT JOURNAL OF CHEMICAL PHYSICS Sitz, G. O., Kummel, A. C., Zare, R. N. 1988; 89 (4): 2558-2571

    View details for Web of Science ID A1988P638800090

  • DETERMINATION OF POPULATION, ALIGNMENT, AND ORIENTATION USING LASER-INDUCED FLUORESCENCE WITH UNRESOLVED EMISSION JOURNAL OF CHEMICAL PHYSICS Kummel, A. C., Sitz, G. O., Zare, R. N. 1988; 88 (12): 7357-7368

    View details for Web of Science ID A1988N786200011

  • STARK-EFFECT STUDIES IN XENON AUTO-IONIZING RYDBERG STATES USING A TUNABLE EXTREME-ULTRAVIOLET LASER SOURCE PHYSICAL REVIEW A Ernst, W. E., Softley, T. P., Zare, R. N. 1988; 37 (11): 4172-4183

    View details for Web of Science ID A1988N755500014

  • DETERMINATION OF ORIENTATION OF THE GROUND-STATE USING 2-PHOTON NONRESONANT EXCITATION JOURNAL OF CHEMICAL PHYSICS Kummel, A. C., Sitz, G. O., Zare, R. N. 1988; 88 (11): 6707-6732

    View details for Web of Science ID A1988N666400004

  • DETERMINATION OF METHOTREXATE AND ITS MAJOR METABOLITE, 7-HYDROXYMETHOTREXATE, USING CAPILLARY ZONE ELECTROPHORESIS AND LASER-INDUCED FLUORESCENCE DETECTION JOURNAL OF CHROMATOGRAPHY-BIOMEDICAL APPLICATIONS Roach, M. C., GOZEL, P., Zare, R. N. 1988; 426 (1): 129-140

    Abstract

    High-dosage methotrexate therapy requires careful monitoring of the drug in serum to ensure minimal toxic effects. A simple, rapid and sensitive method for the separation and quantitation of methotrexate and its major metabolite, 7-hydroxymethotrexate, using high-voltage capillary zone electrophoresis combined with laser-induced fluorescence detection is described. The detection limit for methotrexate is as low as 5.10(-10) M (signal-to-noise ratio = 3), while that for 7-hydroxymethotrexate is 2.10(-9) M. The linearity of the system extends over nearly four orders of magnitude for both methotrexate and 7-hydroxymethotrexate. The extraction efficiency for the drug and its metabolite from serum is 80-85% using a Sep-Pak C18 cartridge. Quantitation of methotrexate in serum was possible in the 10(-10) M range, nearly two orders of magnitude lower than that currently obtainable by existing methods. Good correlation (r = 0.99) for serum methotrexate concentrations was obtained with an enzyme-multiplied immunoassay technique. Comparison with an enzyme inhibition assay also provided similar results.

    View details for Web of Science ID A1988M968800014

    View details for PubMedID 3384865

  • 2-STEP LASER MASS-SPECTROMETRY FOR DIRECT MIXTURE-ANALYSIS CHIMIA Zenobi, R., Hahn, J. H., Zare, R. N. 1988; 42 (4): 147-149

    View details for Web of Science ID A1988N275200010

  • APPLICATION OF 2-STEP LASER MASS-SPECTROMETRY TO COSMOGEOCHEMISTRY - DIRECT ANALYSIS OF METEORITES SCIENCE Hahn, J. H., Zenobi, R., Bada, J. L., Zare, R. N. 1988; 239 (4847): 1523-1525

    Abstract

    Polycyclic aromatic hydrocarbons in C1, C2, and C3 carbonaceous chondrites and in some ordinary chondrites have been directly analyzed by two-step laser desorption/ laser multiphoton ionization mass spectrometry, a selective and sensitive method requiring only milligram samples. At the ionization wavelength of 266 nanometers, parent ion peaks of polycyclic aromatic hydrocarbons dominate the mass spectra. Quantitative analysis is possible; as an example, the concentration of phenanthrene in the Murchison meteorite was determined to be 5.0 parts per million.

    View details for Web of Science ID A1988M615900028

    View details for PubMedID 17772750

  • QUANTITATION OF LI+ IN SERUM BY CAPILLARY ZONE ELECTROPHORESIS WITH AN ON-COLUMN CONDUCTIVITY DETECTOR JOURNAL OF CHROMATOGRAPHY-BIOMEDICAL APPLICATIONS Huang, X. H., Gordon, M. J., Zare, R. N. 1988; 425 (2): 385-390

    View details for Web of Science ID A1988M849100016

    View details for PubMedID 3372649

  • MAGNETIC-SUSCEPTIBILITY MEASUREMENTS USING A LASER PENDULUM APPARATUS JOURNAL OF CHEMICAL EDUCATION Spencer, B., Zare, R. N. 1988; 65 (3): 277-279

    View details for Web of Science ID A1988M756700048

  • BIAS IN QUANTITATIVE CAPILLARY ZONE ELECTROPHORESIS CAUSED BY ELECTROKINETIC SAMPLE INJECTION ANALYTICAL CHEMISTRY Huang, X. H., Gordon, M. J., Zare, R. N. 1988; 60 (4): 375-377

    View details for Web of Science ID A1988M150600023

  • COMPARISON OF OVERTONE-INDUCED AND ELECTRONIC PHOTOCHEMISTRY OF LIQUID TERT-BUTYL HYDROPEROXIDE - SUPPORTING EVIDENCE FOR VIBRATIONAL-MODE SELECTIVITY JOURNAL OF PHYSICAL CHEMISTRY Gutow, J. H., Klenerman, D., Zare, R. N. 1988; 92 (1): 172-177

    View details for Web of Science ID A1988L789900037

  • STERN,OTTO AND THE DOUBLE BANK SHOT ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS Zare, R. N. 1988; 10 (2-3): 377-382

    View details for Web of Science ID A1988R076900033

  • Direct Inelastic Scattering of N2 from Ag(111). III. Normal Incident N2 J. Chem. Phys. Kummel, A. C., Sitz, G. O., Zare, R. N., Tully, J. C. 1988; 89: 6947-6955
  • Surface Temperature Measurement of Dielectric Materials Heated by Pulsed Laser Radiation Chemistry Physical Letters Zenobi, R., Hahn, J. H., Zare, R. N. 1988; 150: 361-365
  • A Nomenclature for Λ Doublet Levels in Rotating Linear Molecules J. Chem. Phys. Alexander, M. H., et al 1988; 89: 1749-1753
  • Otto Stern and the Double Bank Shot Z. Phys. D Zare, R. N. 1988; 10: 377-382
  • Zweistufige Laser- Massenspektrometrie fur die Direkte Analytik von Gemischen Chimia Zenobi, R., Hahn, J. H., Zare, R. Z. 1988; 42: 147-149
  • Dynamics of the Reaction O(3P) + HBr: Experimental Investigation and Theoretical Modeling J. Phys. Chem. McKendrick, K. G., Rakestraw, D. J., Zhang, R., Zare, R. N. 1988; 92: 5530-5540
  • Application of Two-Step Laser Mass Spectrometry to Cosmogeochemistry: Direct Analysis of Meteorites Science Hahn, J. H., Zenobi, R., Bada, J. L., Zare, R. N. 1988; 239: 1523-1525
  • MASS-SPECTROMETRY OF MOLECULAR ADSORBATES USING LASER DESORPTION LASER MULTIPHOTON IONIZATION BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Zare, R. N., Hahn, J. H., Zenobi, R. 1988; 61 (1): 87-92

    View details for Web of Science ID A1988M800600011