A high-pressure mass spectrometric and density functional theory investigation of the thermochemical properties and structure of protonated dimers and trimers of glycine.
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.
Raspopov
Serguei A
SA
Department of Chemistry, University of Waterloo, Ontario, Canada, N2L 3G1.
McMahon
Terrance B
TB
D006033:Glycylglycine / Q000737:chemistry*; D007477:Ions; D013058:Mass Spectrometry / Q000379:methods*; D009842:Oligopeptides / Q000737:chemistry*; D011312:Pressure; D011522:Protons; D013816:Thermodynamics; D014835:Volatilization
D007477:Ions; D009842:Oligopeptides; D011522:Protons; D006033:Glycylglycine; C035647:glycyl-glycyl-glycine