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Electron capture dissociation of b 2+ peptide fragments reveals the presence of the acylium ion structure
Author(s) -
Haselmann Kim F.,
Budnik Bogdan A.,
Zubarev Roman A.
Publication year - 2000
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 - 10.1002/1097-0231(20001215)14:23<2242::aid-rcm158>3.0.co;2-o
Subject(s) - chemistry , ion , protonation , dissociation (chemistry) , oxazolone , molecule , crystallography , ab initio , organic chemistry
Electron capture dissociation (ECD) of peptides and their fragments has now been extended to bn2+ ions, where it also produced far more structural information than collisional activation. Interestingly, bn2+ ions revealed abundant loss of CO from radical monocations and the presence of c(n − 1)+. fragments. The CO loss from peptide radical cations is unusual and was attributed to neutralization of the −C≡O + group in the acylium ion structure, supported by the observation of c(n − 1)+. ions that can only be formed from an open‐chain ion. These characteristic features were most prominent for b 12 2+ ions of renin substrate and least prominent for bn2+ ions of substance P (n = 9,10). Totally, out of seven bn2+ ions studied, CO loss above 3% level was present in all spectra as well as c(n − 1 )+. fragments of three species, suggesting that the acylium ion structure plays a significant role for at least some b 2+ ions. This is an unexpected result in view of the literature data for small, singly charged b ions, for which the protonated oxazolone structure is favoured in ab initio calculations. Apparently, more studies are required before extrapolating the small molecule results to large species. The CO loss in ECD can be used for distinguishing between b and y ions in the MS/MS spectrum of larger molecules. Copyright © 2000 John Wiley & Sons, Ltd.