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Identification of leucine‐enkephalin radical oxidation products by liquid chromatography tandem mass spectrometry
Author(s) -
Fonseca Conceição,
Domingues Pedro,
Reis Ana,
Domingues M. Rosário M.
Publication year - 2008
Publication title -
biomedical chromatography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 65
eISSN - 1099-0801
pISSN - 0269-3879
DOI - 10.1002/bmc.1014
Subject(s) - chemistry , chromatography , tandem mass spectrometry , mass spectrometry , leucine , liquid chromatography–mass spectrometry , tandem , isobaric labeling , protein mass spectrometry , amino acid , biochemistry , materials science , composite material
The oxidation of the peptide leucine‐enkephalin (YGGFL) induced by the hydroxyl radical (HO • ), formed under Fenton‐like conditions [Cu (II)/H 2 O 2 ], was studied and monitored by LC‐MS. The oxidation products identified included products resultant from (a) the insertion of oxygen atoms (1–5), (b) peptide backbone cleavage (short‐chain products formed by diamide pathway) and (c) radical–radical crosslinking reactions. In order to identify the modified residues, LC‐MS/MS spectra were obtained. The insertion of oxygen atoms into the peptide originated hydroxide, di‐hydroxide and/or hydroperoxide derivatives. In addition it was found that the aromatic amino acids are most susceptible to being hydroxylated, while the aliphatic amino acids are more prone to forming hydroperoxides. Oxidation products with double bonds were also identified. The short chain products resulted from the α ‐carbon radical of terminal amino acids (Tyr and Leu). Products resulting from cross‐linking reactions between intact carbon‐centered peptide radical (with and without one HO group) and a side chain radical ( • C 7 H 7 O) were identified. It was found that, although all amino acids residues of the peptide undergo modifications, the N‐terminal seems to be prone to oxidative modifications under these conditions. Copyright © 2008 John Wiley & Sons, Ltd.