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Amide bond cleavage in deprotonated tripeptides: a newly discovered pathway to ″b 2 ions
Author(s) -
Harrison Alex G.,
Michael Siu K. W.,
El Aribi Houssain
Publication year - 2003
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.988
Subject(s) - chemistry , fragmentation (computing) , tripeptide , deprotonation , ion , amine gas treating , amide , medicinal chemistry , mass spectrometry , hydrogen , stereochemistry , peptide , organic chemistry , chromatography , computer science , operating system , biochemistry
The fragmentation reactions of the [MH] − ions of the tripeptides H‐Gly‐Leu‐Sar‐OH, H‐Leu‐Gly‐Pro‐OH and H‐Gly‐Leu‐Gly‐OH have been investigated in detail using energy‐resolved mass spectrometry, isotopic labelling and MS 3 experiments. It is shown that the major route to the ″b 2 ions involves loss of a neutral amine from the a 3 ([MHCO 2 ] − ) ion rather than being formed directly by fragmentation of the [MH] − ion. When there is no C‐terminal amidic hydrogen (Sar, Pro), loss of a neutral amine is the dominant primary fragmentation reaction of the a 3 ion. However, when there is a C‐terminal amidic hydrogen (Gly), elimination of the N‐terminal amino acid residue is the major fragmentation reaction of the a 3 ion and formation of the ″b 2 ion is greatly reduced in importance. It is proposed that the ″b 2 ions are deprotonated oxazolones. Copyright © 2003 John Wiley & Sons, Ltd.