A high-pressure mass spectrometric and density functional theory investigation of the thermochemical properties and structure of protonated dimers and trimers of glycine

• Published in: Journal of mass spectrometry Vol. 40; no. 12; pp. 1536 - 1545
• Main Authors: Raspopov, Serguei A., McMahon, Terrance B.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.12.2005; Wiley
• Subjects: Chemistry; cluster energetics; cluster structures; clustering thermochemistry; Exact sciences and technology; Glycylglycine - chemistry; intramolecular hydrogen bonding; Ions; Mass spectrometry; Mass Spectrometry - methods; Oligopeptides - chemistry; Organic chemistry; Pressure; protonated glycine; protonated glycine dimer and trimer; Protons; Reactivity and mechanisms; Thermodynamics; Volatilization; Trimer; protonated glycine; cluster energetics; Molecular cluster; Theoretical study; clustering thermochemistry; Glycine; Operating conditions; α-Aminoacid; Thermochemical properties; Pressure effect; Protonated form; Density functional method; intramolecular hydrogen bonding; Dimer; protonated glycine dimer and trimer; Gas phase; cluster structures; Intramolecular hydrogen bond; Mass spectrometry
• ISSN: 1076-5174; 1096-9888
• DOI: 10.1002/jms.908

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. Copyright © 2005 John Wiley & Sons, Ltd.