Premium
Gas‐phase ion chemistry of Glu/Met systems
Author(s) -
Wincel H.,
Fokkens R. H.
Publication year - 2001
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.540
Subject(s) - chemistry , protonation , adduct , fragmentation (computing) , ion , mass spectrometry , dimer , molecule , mass spectrum , tandem mass spectrometry , proton affinity , proton , chemical ionization , crystallography , ionization , organic chemistry , chromatography , computer science , physics , quantum mechanics , operating system
Abstract A combined chemical ionisation and tandem mass spectrometry (MS/MS) approach has been used for investigation of the gas‐phase ion chemistry of systems containing the amino acids Glu and Met, and the dipeptides γ‐Glu‐Met and Met‐Glu. The metastable fragmentation of the protonated dimer, (Glu) 2 H + , reveals an intracluster reaction leading to the elimination of the Glu residue. The main features of the ion‐molecule reactions observed in the systems containing Glu and Glu + Met can be described in terms of sequential adduct formation. The results obtained for the thermal dehydration of Glu were used to rationalise the formation of the proton‐bound structures (Glu − H 2 O)···H + ··· (Glu − H 2 O) and (Glu − H 2 O) 3 ·H + . The adduct ions, [(Glu − H 2 O) + H + Glu] + and [(Glu − H 2 O) + H + Met] + , and further association products were also observed. The results lead to a reconsideration of the structural aspects proposed earlier for these species in the sense that they suggest that the systems correspond to a mixture of isomeric covalent and proton‐bound structures. The thermal effects on the decomposition of the neutral (γ‐Glu‐Met) and its protonated form, (γ‐Glu‐Met)H + , at m/z 279 were investigated, and dramatic changes in the MI spectra of the m/z 279 ion with temperature were found. A mechanistic explanation for the observed evolution of higher mass ion peaks in the mass spectra is developed. Copyright © 2001 John Wiley & Sons, Ltd.