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https://hdl.handle.net/2440/51293
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Type: | Journal article |
Title: | Negative ion fragmentations of deprotonated peptides containing post-translational modifications. An unusual cyclisation/rearrangement involving phosphotyrosine; a joint experimental and theoretical study |
Author: | Wang, T. Andreazza, H. Bilusich, D. Bowie, J. |
Citation: | Rapid Communications in Mass Spectrometry, 2009; 23(11):1669-1677 |
Publisher: | John Wiley & Sons Ltd |
Issue Date: | 2009 |
ISSN: | 0951-4198 1097-0231 |
Statement of Responsibility: | Tianfang Wang, Hayley J. Andreazza, Daniel Bilusich and John H. Bowie |
Abstract: | The characteristic fragmentations of a pTyr group in the negative ion electrospray mass spectrum of the [M-H](-) anion of a peptide or protein involve the formation of PO(3) (-) (m/z 79) and the corresponding [(M-H)(-)-HPO(3)](-) species. In some tetrapeptides where pTyr is the third residue, these characteristic anion fragmentations are accompanied by ions corresponding to H(2)PO(4) (-) and [(M-H)(-)-H(3)PO(4)](-) (these are fragmentations normally indicating the presence of pSer or pThr). These product ions are formed by rearrangement processes which involve initial nucleophilic attack of a C-terminal -CO(2) (-) [or -C(==NH)O(-)] group at the phosphorus of the Tyr side chain [an S(N)2(P) reaction]. The rearrangement reactions have been studied by ab initio calculations at the HF/6-31+G(d)//AM1 level of theory. The study suggests the possibility of two processes following the initial S(N)2(P) reaction. In the rearrangement (involving a C-terminal carboxylate anion) with the lower energy reaction profile, the formation of the H(2)PO(4) (-) and [(M-H)(-)-H(3)PO(4)](-) anions is endothermic by 180 and 318 kJ mol(-1), respectively, with a maximum barrier (to a transition state) of 229 kJ mol(-1). The energy required to form H(2)PO(4) (-) by this rearrangement process is (i) more than that necessary to effect the characteristic formation of PO(3) (-) from pTyr, but (ii) comparable with that required to effect the characteristic alpha, beta and gamma backbone cleavages of peptide negative ions. |
Keywords: | Phosphotyrosine Peptides Protein Processing, Post-Translational Cyclization Models, Theoretical Models, Chemical Mass Spectrometry |
Description: | Copyright © 2009 John Wiley & Sons, Ltd. |
DOI: | 10.1002/rcm.4061 |
Grant ID: | ARC |
Published version: | http://dx.doi.org/10.1002/rcm.4061 |
Appears in Collections: | Aurora harvest Chemistry and Physics publications |
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