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An investigation of fragmentation mechanisms of doubly protonated tryptic peptides
Author(s) -
Tang XueJun,
Boyd Robert K.,
Bertrand M. J.
Publication year - 1992
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.1290061105
Subject(s) - chemistry , protonation , ion , fragmentation (computing) , intramolecular force , trypsin , crystallography , peptide , hydrolysis , dissociation (chemistry) , mass spectrometry , stereochemistry , enzyme , chromatography , organic chemistry , biochemistry , computer science , operating system
Peptides formed as reaction products, of specific hydrolysis of proteins by trypsin, are characterized by a basic residue (Arg or Lys) as the C‐terminus, which facilitates formation of bundant [M+2H] 2+ ions under electrospray r ionspry conditions. These doubly charged ions readily dissociate upon collisional activation to y" and b fragment ions which are mass complemens of one another. The suggestion tht these fragments are formed by direct charge‐separation disociatons must contend with the observation that the y" intensities are generaly appreciably larger than those of their b counterparts. However, it is shown that this can be accouned for by a greater susceptibility f the b ions to undergo further dissociaton to smaler fragments such as immonium ions. In addition no evidence could be found to support alternative mechanisms, including dissociative electron capture, for which equal intensities of the two fragment ion series are not obligatory. Initial protonation at the N‐terminus was shown to be required for formation of these [M+2H] 2+ ions via its suppression by mono‐acetylation at the N‐terminus. These findings, and others concerning formation of [y"′] 2+ fragments from singly protonated peptides, via charge‐site‐induced cleavages and intramolecular proto transfers between nitrogen atoms, respectively.