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Collision‐induced dissociation of protonated tetrapeptides containing β ‐alanine, γ ‐aminobutyric acid, ϵ ‐aminocaproic acid or 4‐aminomethylbenzoic acid residues
Author(s) -
Talaty Erach R.,
Cooper Travis J.,
Osburn Sandra,
Van Stipdonk Michael J.
Publication year - 2006
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.2754
Subject(s) - chemistry , protonation , alanine , dissociation (chemistry) , aminobutyric acid , amino acid , stereochemistry , biochemistry , organic chemistry , ion , receptor
Abstract The influence of the presence and position of a single β ‐alanine, γ ‐aminobutyric acid, ϵ ‐aminocaproic acid or 4‐aminomethylbenzoic acid residue on the tendency to form b n + ‐ and y n + ‐type product ions was determined using a group of protonated tetrapeptides with general sequence XAAG, AXAG and AAXG (where X refers to the position of amino acid substitution). The hypothesis tested was that the ‘alternative’ amino acids would influence product ion signal intensities by inhibiting or suppressing either the nucleophilic attack or key proton transfer steps by forcing the adoption of large cyclic intermediates or blocking cyclization altogether. We found that specific b ions are diminished or eliminated completely when β A, γ Abu, Cap or 4AMBz residues are positioned such that they should interfere with the intramolecular nucleophilic attack step. In addition, differences in the relative proton affinities of the alternative amino acids influence the competition between complementary b n and y n ions. For both the AXAG and the XAAG series of peptides, collision‐induced dissociation (CID) generated prominent b ions despite potential inhibition or suppression of intramolecular proton migration by the β A, γ Abu, Cap or 4AMBz residues. The prominent appearance of b ions from the AXAG and XAAG peptide is noteworthy, and suggests either that proton migration occurs through larger, ‘whole’ peptide cyclic intermediates or that fragmentation proceeds through a population of [M+H] + isomers that are initially protonated at amide O atoms. Copyright © 2006 John Wiley & Sons, Ltd.