Gas phase H/D exchange of sodiated amino acids: why do we see zwitterions?

Rožman, Marko; Bertoša, Branimir; Klasinc, Leo; Srzić, Dunja (2006) Gas phase H/D exchange of sodiated amino acids: why do we see zwitterions?. Journal of The American Society for Mass Spectrometry, 17 (1). pp. 29-36. ISSN 1044-0305

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Abstract

The gas-phase interaction of sodiated amino acids and sodiated amino acid methyl esters with various deuterium donors is investigated by combining results of H/D exchange reactions with those from density functional theory and molecular dynamics calculations. Discrepancy between experimentally and theoretically obtained structures for sodium cationized amino acids is explained by deuterium donor caused perturbation of the most stable amino acid conformation. Detailed study of H/D exchange mechanism on sodiated amino acids shows that the H/D exchange reaction is preceded by a multistep quasi-isoenergetic transition (perturbation) from a charge solvated to zwitterionic structure in the amino acid. Although the computation refers to the system AlaNa+ and D2O, these mechanisms apply to all amino acids, except those where a functional side-chain group takes part in the perturbation process. The suggested perturbation mechanism applies also for other deuterium donors such as CD3OD or even ND3 and indicates that a single water molecule suffices to convert the sodiated amino acid from charge solvated to zwitterionic form.

Item Type:	Article
Uncontrolled Keywords:	H/D exchange; sodiated amino acids; reaction mechanism
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Physical Chemistry
Depositing User:	Kristina Ciglar
Date Deposited:	18 Jan 2017 14:41
URI:	http://fulir.irb.hr/id/eprint/3323
DOI:	10.1016/j.jasms.2005.08.017

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