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Fragmentation of the deprotonated ions of peptides containing cysteine, cysteine sulfinic acid, cysteine sulfonic acid, aspartic acid, and glutamic acid
Author(s) -
Men Lijie,
Wang Yinsheng
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.2374
Subject(s) - chemistry , cysteine , aspartic acid , fragmentation (computing) , sulfonic acid , deprotonation , cysteic acid , glutamic acid , sulfinic acid , biochemistry , amino acid , ion , cystine , organic chemistry , enzyme , computer science , operating system
We examined the fragmentation of the electrospray‐produced [M–H] − and [M–2H] 2− ions of a number of peptides containing two acidic amino acid residues, one being aspartic acid (Asp) or glutamic acid (Glu), and the other being cysteine sulfinic acid [C(SO 2 H)] or cysteine sulfonic acid [C(SO 3 H)], on an ion‐trap mass spectrometer. We observed facile neutral losses of H 2 S and H 2 SO 2 from the side chains of cysteine and C(SO 2 H), respectively, whereas the corresponding elimination of H 2 SO 3 from the side chain of C(SO 3 H) was undetectable for most peptides that we investigated. In addition, the collisional activation of the [M–H] − ions of the C(SO 2 H)‐containing peptides resulted in the cleavage of the amide bond on the C‐terminal side of the C(SO 2 H) residue. Moreover, collisional activation of the [M–2H] 2− ions of the above Asp‐containing peptides led to the cleavage of the backbone N‐C α bond of the Asp residue to give c n and/or its complementary [z n –H 2 O] ions. Similar cleavage also occurred for the singly deprotonated ions of the otherwise identical peptides with a C‐terminal amide functionality, but not for the [M–H] − ions of same peptides with a free C‐terminal carboxylic acid. Furthermore, ab initio calculation results for model cleavage reactions are consistent with the selective cleavage of the backbone N–C α bond in the Asp residue. Copyright © 2006 John Wiley & Sons, Ltd.