Part 50 of the series ‘Gas Phase Ion Chemistry of Biomolecules’.
Peptide derivatization as a strategy to form fixed-charge peptide radicals†
Article first published online: 30 AUG 2006
Copyright © 2006 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 20, Issue 19, pages 2865–2870, 15 October 2006
How to Cite
Karnezis, A., Barlow, C. K., O'Hair, R. A. J. and McFadyen, W. D. (2006), Peptide derivatization as a strategy to form fixed-charge peptide radicals. Rapid Commun. Mass Spectrom., 20: 2865–2870. doi: 10.1002/rcm.2671
- Issue published online: 30 AUG 2006
- Article first published online: 30 AUG 2006
- Manuscript Revised: 17 JUL 2006
- Manuscript Accepted: 17 JUL 2006
- Manuscript Received: 15 JUN 2006
- Australian Research Council. Grant Number: DP0344145
As a means of generating fixed-charge peptide radicals in the gas phase we have examined the collision-induced dissociation (CID) chemistry of ternary [CuII(terpy)(TMPP-M)]2+ complexes, where terpy = 2,2′:6′2″-terpyridine and TMPP-M represents a peptide (M) modified by conversion of the N-terminal amine to a [tris(2,4,6-trimethoxyphenyl)phosphonium]acetamide (TMPP-) fixed-charge derivative. The following modified peptides were examined: oligoglycines, (Gly)n (n = 1–5), alanylglycine, glycylalanine, dialanine, trialanine and leucine-enkephaline (YGGFL). The [CuII(terpy)(TMPP-M)]2+ complexes are readily formed upon electrospray ionization (ESI) of a mixture of derivatized peptide and [CuII(terpy)(NO3)2] and generally fragment to form transient peptide radical cations, TMPP-M+., which undergo rapid decarboxylation for the simple aliphatic peptides. This is contrasted with the complexes containing the unmodified peptides, which predominantly undergo fragmentation of the coordinated peptide. These differences demonstrate the importance of proton mobility in directing fragmentation of ternary copper(II) peptide complexes. In the case of leucine-enkephaline, a sufficient yield of the radical cation was obtained to allow further CID. The TMPP-YGGFL+. ion showed a rich fragmentation chemistry, including CO2 loss, side-chain losses of an isopropyl radical, 2-methylpropene and p-quinomethide, and *a1 and *a4 sequence ion formation. In contrast, the even-electron TMPP-YGGFL+ ion fragments to form *an and *bn sequence ions as well as the [*b4 + H2O]+ rearrangement ion. Copyright © 2006 John Wiley & Sons, Ltd.