个人简介

Harvard College - A.B. (1968) California Institute of Technology - Ph.D. (1973)

研究领域

Organic Chemistry/Chemical Biology/Computational Chemistry

For many years chemists have theorized that the peculiarities of enzyme active sites and biological receptors can be ascribed to the fact that they provide reaction media that differ greatly from bulk solvent. One hypothesis, originally put forth about 35 years ago, holds that the gas phase represents the closest analogy to the milieux of binding sites in proteins. Our research group is one of the few in the world that is seeking to replace speculation with fact by pursuing concurrent studies of organic reactions in the gas phase and in biological receptors. In this work we make use of (and, in some cases, have invented) new techniques in mass spectrometry, as well as novel methods for tagging and purifying receptors. Biological Receptor Sites Our focus has been on the binding and recognition of small (m.w. <250), electrically uncharged molecules. We have been especially interested in receptors for the sense of smell in vertebrate species. Since very little is known about these receptors, new chemistry has been devised for in vivo study. We can make educated guesses about mechanisms for molecular recognition and binding specificity. For receptors that identify small, nonpolar molecules, molecular shape does not offer enough information for a binding site to distinguish different compounds. Other kinds of information, including chemical reactivity, must play a role. In the sense of smell, we have uncovered evidence that Schiff base formation (shown above), plays a role in olfactory detection of ketone-containing odorants. This chemistry is being explored with a number of new approaches, including Two-Step Affinity Chromatography and Accelerator Mass Spectrometry. mortondesign1 This chemistry is being explored with a number of new approaches, including Two-Step Affinity Chromatography and Accelerator Mass Spectrometry. Gas Phase Organic Chemistry Electrically charged organic molecules enjoy a vastly different environment in the gas phase than in bulk solvent. Solvation is negligible, and counterions are absent. Chemical reactions take place on a timescale that is much faster than the timescale for exchange of energy with the ambient heat bath. Despite these substantial differences, we have found at least one major feature of gas phase ion chemistry that bears a strong resemblance to reactions in solution: a charged and an uncharged molecule experience encounters of long duration, in which a variety of orientations are explored prior to chemical reaction. Therefore, the outcome of an ionic reaction in the gas phase is not determined by the physics of collision so much as by the chemistry of the reactants. Many techniques are used at UCR to probe the stereo- and regiochemistry of the reactions of organic ions in the gas phase, among them EBFlow (for examining the neutral products of ionic reactions in the gas phase) and the whole range of modern instrumental methods in NMR and Mass Spectrometry. We have found out that SN2 displacements go by backside attack in the gas phase, just as they do in solution. In general, we are discovering aspects of gas phase chemistry that ought to hold true for reactions in biological media as well.

近期论文

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Proton-Bridge Motions in Amine Conjugate Acid Ions Having Intramolecular Hydrogen Bonds to hydroxyl and Amine Groups Oomens, J., Morton, T.H. "Fluoronium Metathesis and Rearrangements of Fluorine-Stabilized Carbocations" International Journal of Mass Spectrometry (2011) 308, 232-238. Oomens, J., Morton, T.H. "Aldehyde and Ketone Adducts of the Gaseous Trifluoromethyl Cation" OrganicLetters (2011) 13, 2176-2179. Morton, T.H., Weber, K., Zhang, J. "Thermal decomposition of t-amyl methyl ether studied by flash pyrolysis/supersonic expansion/vacuum ultraviolet photoionization time-of-flight masss spectrometry" International Journal of Mass Spectrometry (2011) 306, 210-218. Morton, T.H. "Gas phase infrared spectra of small polyatomic ions as a benchmark for theory" InorganicaChimica Acta (2011) 369, 140-145. Journal: Oomens, J., Moehlig, A.R., Morton, T.H. "Infrared multiple photon dissociation (IRMPD) spectroscopy of the proton-bound dimer of 1-methylcytosine in the gas phase" Journal of Physical Chemistry Letters (2010) 1, 2891-2897. Oomens, J., Steill, J., Morton, T.H. "IR Spectra of Boron-Stabilized Anions in the Gas Phase" Inorganic Chemistry (2010) 49, 6781-6783. Oomens, J., Morton, T.H. "Structures of Products from Positive Ion-Molecule Reactions by Means of Vibrational Spectroscopy" European Journal of Mass Spectrometry (2010) 16, 313-319. A.E. Engelhart, T.H, Morton, and N.V. Hud, "Evidence of Strong Hydrogen Bonding in 8-Aminoguanine." Chem. Comm. 2009, 647-649. I. Lee, M.K. Nguyen, T.H. Morton, and F. Zaera, F. "Thermal Chemistry of 1,4-Difluoro-2-butenes on Pt(111) Single-Crystal Surfaces." J. Phys. Chem. C 2008, 112, 14117-14123. J. Oomens, E. Kraka, M.K. Nguyen, and T.H. Morton, "Structure, Vibrational Spectra, and Unimolecular Dissociation of Gaseous 1-Fluoro-1-phenethyl Cations" J. Phys. Chem. A 2008, 112, 10774-10783. T. Cao, M.K. Nguyen, S.V. Serafin, and T.H. Morton, "Stereochemical Preferences in Synclinal 4-Center Eliminations from Gaseous Ions" J. Org. Chem. 2008, 73, 6099-6107. S. Yaghmaei, S. Khodagholian, J.M. Kaiser, F.S. Tham, F.S., L.J. Mueller, and T.H. Morton. "Chelation of a Proton by an Aliphatic Tertiary Diamine." J. Am. Chem. Soc. 2008, 130, 7836-7838. J. Oomens and T.H. Morton "The Cationic C=F+ Stretching Frequency." Angewandte Chemie International Edition2008, 47, 2106-2108. N.V. Hud and T.H. Morton "DFT Energy Surfaces for Aminopurine Homodimers and their Conjugate Acid Ions," J. Phys. Chem. A 2007, 111, 3369-3377. M..J. McEwan, P.F. Wilson, G.J. Francis,and T.H. Morton "Transfer of F+ versus Fluoronium Metathesis. Competing Reactivities of the Gaseous Fluoroformyl Cation" Int. J. Mass Spectrom. 2007, 267, 81-88. R.R. Julian, T. Ly, A.-M. Finaldi, and T.H. Morton "Dissociation of a Protonated Secondary Amine in the Gas Phase via an Ion-Neutral Complex" Int. J. Mass Spectrom. 2007, 265, 302-307. K. Weber, J. Zhang, D. Borchardt, and T.H. Morton,"Pyrolysis of 2-methoxy-2,3,3-trimethylbutane (MTMB) monitored by 118nm photoionization mass spectrometry." Int. J. Mass Spectrom. 2006, 249-250, 303-310. J.C. Traeger and T.H. Morton, "Activation Barriers for Addition of Methyl Radicals to Oxygen-Stabilized Carbocations," J. Phys. Chem. A 2005, 109, 10467-10473 Scott V. Serafin, Rhonda Maranan, Kangling Zhang, and Thomas Hellman Morton*, "Mass Spectrometric Differentiation Of Linear Peptides Composed Of L-Amino Acids From Isomers Containing One D-Amino Acid Residue" Analytical Chemistry, (2005) 77, 5480-5487. Scott V. Serafin, Kangling Zhang, Luigi Aurelio, Andrew B. Hughes, and Thomas Hellman Morton, "Decomposition of Protonated Threonine, Its Stereoisomers, and Its Homologues in the Gas Phase: Evidence for Internal Backside Displacement", Organic Letters. 2004, 6, 1561-1564. T.H. Morton, "Theoretical Models for Ion-Neutral Complexes in Unimolecular Ion Decompositions", Encyclopedia of Mass Spectrometry, Volume 4 (N.M.M. Nibbering, ed.) 2004, 165-173. T.H. Morton, "Mass Spectrometric Discrimination of Acyclic Stereoisomers via Competing Unimolecular Decompositions", Encyclopedia of Mass Spectrometry, Volume 4 (N.M.M. Nibbering, ed.) 2004, 433-443. John C. Traeger and Thomas Hellman Morton, "Photoionization of 2,3-Dimethyl-2-Butanol (Thexyl Alcohol): Interaction Between the Charged and Expelled Fragments", Journal of the American Society for Mass Spectrometry. 2004, 15, 989-997.