Inverse Hydrogen Migration in Arginine-Containing Peptide Ions upon Electron Transfer

被引：0

作者：

Panja, Subhasis ^{[1
]}

Nielsen, Steen Brøndsted ^{[1
]}

Hvelplund, Preben ^{[1
]}

Turecek, František ^{[2
]}

机构：

[1] Department of Physics and Astronomy, University of Aarhus, Denmark

[2] Department of Chemistry, University of Washington, Seattle, WA, United States

来源：

Journal of the American Society for Mass Spectrometry | 2008年 / 19卷 / 12期

关键词：

Collisional electron transfer from gaseous Cs atoms was studied for singly and doubly protonated peptides Gly-Arg (GR) and Ala-Arg (AR) at 50- and 100-keV kinetic energies. Singly protonated GR and AR were discharged to radicals that in part rearranged by migration of a Cα hydrogen atom onto the guanidine group. The Cα-radical isomers formed were detected as stable anions following transfer of a second electron. In addition to the stabilizing rearrangements; the radicals underwent side-chain and backbone dissociations. The latter formed z fragments that were detected as the corresponding anions. Analysis of the (GR + H)· radical potential energy surface using electronic structure theory in combination with Rice-Ramsperger-Kassel-Marcus calculations of rate constants indicated that the arginine Cα hydrogen atom was likely to be transferred to the arginine side-chain on the experimental timescale of ≤200 ns. Transfer of the Gly Cα{single bond}H was calculated to have a higher transition-state energy and was not kinetically competitive. Collisional electron transfer to doubly protonated GR and AR resulted in complete dissociation of (GR + 2H)+· and (AR + 2H)+· ions by loss of H; ammonia; and N{single bond}Cα bond cleavage. Electronic structure theory analysis of (GR + 2H)+· indicated the presence of multiple conformers and electronic states that differed in reactivity and steered the dissociations to distinct channels. Electron attachment to (GR + 2H)2+ resulted in the formation of closely spaced electronic states of (GR + 2H)+· in which the electron density was delocalized over the guanidinium; ammonium; amide; and carboxyl groups. The different behavior of (GR + H)· and (GR + 2H)+· is explained by the different timescales for dissociation and different internal energies acquired upon electron transfer. © 2008;

D O I：

暂无

中图分类号：

学科分类号：

摘要：

Journal article (JA)

引用

页码：1726 / 1742