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Negative ion fragmentations of deprotonated peptides containing post‐translational modifications: diphosphorylated systems containing Ser, Thr and Tyr. A characteristic phosphate/phosphate cyclisation. A joint experimental and theoretical study
Author(s) -
Andreazza Hayley J.,
Wang Tianfang,
Bilusich Daniel,
Hoffmann Peter,
Bowie John H.
Publication year - 2009
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.4081
Subject(s) - chemistry , deprotonation , phosphate , ion , stereochemistry , nucleophile , exothermic reaction , crystallography , medicinal chemistry , organic chemistry , catalysis
[M–H] − anions from small diphosphopeptides (phosphate groups on Ser, Thr or Tyr) show characteristic peaks corresponding to m/z 177 (H 3 P 2 O 7 − ), 159 (HP 2 O 6 − ) and sometimes [(M‐H) − –H 4 P 2 O 7 ] − . M/z 177 and m/z 159 are major peaks in the spectra of small peptides with 1,2, 1,3, 1,4, 1,5 and 1,6 diphosphate substitution, which means that the decomposing [M–H] − anions must have flexible structures in order for the two phosphate groups to interact with each other. Peptides where the two phosphate groups are more than six amino acid residues apart have not been studied. Theoretical calculations indicate that m/z 177 is formed in a strongly exothermic reaction involving facile nucleophilic interaction between the two phosphate groups: m/z 159 is formed by loss of water from energised m/z 177. Copyright © 2009 John Wiley & Sons, Ltd.