Resonant dissociative electron capture by the simplest amino acids and dipeptides

Abstract

The formation of ions from amino acids (glycine and alanine) and dipeptides (glycylglycine, alanylalanine, and glycylalanine) under the resonant electron capture conditions was studied by negative ion resonant electron capture mass spectrometry. The isobaric ions were found, their effective yield curves were experimentally separated, and the elemental composition was determined. The thermochemical aspect of ion formation was considered, and probable dissociative channels of fragmentation ion formation and their structures were established on the basis of this aspect. Bond cleavage reactions only and H-shift processes were revealed. The rearrangements occur presumably through the stage of formation of intramolecular hydrogen bonds. The cross-sections of formation of ions [M − H]− were measured in the energy range 1.1–1.3 eV. The metastable decay channels of ions [M − H]− and [M − COOH]− were found in the energy range 4.5–7.5 eV for dipeptides, which enabled establishing the genetic relationship between the parental and daughter ions and revealing hidden fragmentation pathways.