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Characterizing degradation products of peptides containing N‐terminal Cys residues by (off‐line high‐performance liquid chromatography)/matrix‐assisted laser desorption/ionization quadrupole time‐of‐flight measurements
Author(s) -
Krokhin Oleg V.,
Ens Werner,
Standing Kenneth G.
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.1236
Subject(s) - chemistry , pyroglutamic acid , peptide , deamidation , chromatography , cysteine , matrix assisted laser desorption/ionization , iodoacetamide , mass spectrometry , residue (chemistry) , high performance liquid chromatography , trifluoroacetic acid , amino acid , desorption , organic chemistry , biochemistry , enzyme , adsorption
A transformation analogous to the well‐known conversion of an N‐terminal glutamine residue to pyroglutamic acid is the cyclization of an N‐terminal carboxamidomethylated cysteine residue (the normal product of alkylation with iodoacetamide). This yields 5‐oxothiomorpholine‐3‐carboxylic acid, with the same 17 Da mass loss observed in the Gln reaction. Nineteen tryptic peptides with Cys at the N‐terminal were identified for this study, and compared with eight with N‐terminal Gln. When examined by MALDI‐QqTOF and (off‐line HPLC)/MALDI‐QqTOF measurements, these were all found to undergo the cyclization reactions. The average degree of degradation during overnight digestion was found to be ∼51 and ∼34% for Cys and Gln, respectively; more detailed information on the time course of the reactions was obtained for the peptides CCTESLVNR and QYYTVFDR. Taking this modification into account while sequencing is likely to increase the probability of protein identification by peptide mass fingerprinting, especially for cysteine‐rich proteins. Copyright © 2003 John Wiley & Sons, Ltd.