Backbone fragmentations of [M–H]– anions from peptides. Reinvestigation of the mechanism of the beta prime cleavage
Article first published online: 10 JUL 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 26, Issue 16, pages 1832–1840, 30 August 2012
How to Cite
Wang, T., Tran, T. T. N., Calabrese, A. N. and Bowie, J. H. (2012), Backbone fragmentations of [M–H]– anions from peptides. Reinvestigation of the mechanism of the beta prime cleavage. Rapid Commun. Mass Spectrom., 26: 1832–1840. doi: 10.1002/rcm.6297
- Issue published online: 2 JUL 2012
- Article first published online: 10 JUL 2012
- Manuscript Accepted: 28 MAY 2012
- Manuscript Revised: 23 MAY 2012
- Manuscript Received: 11 APR 2012
An experimental study has shown that the structure of a β' ion proposed earlier is incorrect. Backbone cleavage β' anions have structures R(NH–) from systems [[RNHCH(X)CONHCH(Y)CO2H (or C-terminal CONH2) – H]– (where R is the rest of the peptide molecule and X and Y represent the α side chains of the individual amino acid residues).
Ab initio calculations were carried out at the CAM-B3LYP/6-311++g(d,p) level of theory.
The calculations suggest that RNH– ions are formed by SNi cyclisation processes involving either (i) the C-terminal CO2– or C-terminal [CONH]– as appropriate, or (ii) an enolate ion [-NHC–(Y)-] cyclising at the backbone CH of the -CH(X)- group. Concomitant C–N bond cleavage then liberates an RNH– ion, processes which can occur along the peptide backbone. Copyright © 2012 John Wiley & Sons, Ltd.