A high-pressure mass spectrometric and density functional theory investigation of the thermochemical properties and structure of protonated dimers and trimers of glycine |
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Authors: | Raspopov Serguei A McMahon Terrance B |
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Affiliation: | Department of Chemistry, University of Waterloo, Ontario, Canada, N2L 3G1. |
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Abstract: | A new modification of pulsed-ionization high-pressure mass spectrometry (PHPMS) has been used to perform equilibrium thermochemical studies for relatively nonvolatile biomolecules such as amino acids. Binding enthalpy and entropy changes have been measured for proton-bound clusters of glycine, which are in good agreement with both theoretical (DFT) results of this work and a previous blackbody infrared dissociation experiment. Experimental data indicate that a number of conformers of the proton-bound dimer of glycine may coexist in the explored temperature range (360-460 K). Several new, conceptually different isomers (two of them zwitterionic) have been found by DFT calculations, one of which is 7 kJ mol(-1) lower in energy than the structure previously reported to be the energy minimum. |
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Keywords: | protonated glycine protonated glycine dimer and trimer clustering thermochemistry cluster structures cluster energetics intramolecular hydrogen bonding |
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