engleski

Gas phase structure of the sodiated amino acids probed by H/D exchange reactions

Taking into account the difference in structure of a sodiated gas phase amino acid in its zwitterionic and charge solvated forms, gas phase structures of sodiated histidine, lysine, phenylalanine, proline, tryptophan and tyrosine were probed by H/D exchange reactions. Experiment results obtained from the site-specific reaction rate constants indicated the zwitterionic structure for all the sodiated amino acids studied. In contrast, B3LYP calculations for sodiated lysine, along with the already presented theoretical results for other amino acids studied, show the charge solvated form to be stable, except for proline which is in the zwitterionic form. Absence of H/D exchange in sodiated methyl esters of phenylalanine and histidine, along with the discrepancy between experimental and theoretical data for the amino acids studied, indicates that H/D exchange occurs only when sodiated amino acids are in the zwitterionic form.

gas phase structure ; sodium cationized amino acids ; sodium cationized amino acid esters ; mass spectrometry ; density functional theory ; zwitterionic structure

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