Peptide nitration by peroxynitrite: Characterisation of the nitration sites by liquid chromatography tandem mass spectrometry

A number of recent studies have demonstrated that peroxynitrite (ONOO-) can react with a host of biomolecules, particularly those containing aromatic amino acid residues, resulting in a number of modifications which have been found in association with diverse pathological conditions, Electrospray io nisation tandem mass spectrometry with and without liquid chromatographic s eparation has been used to examine a series of model peptides following the ir treatment with peroxynitrite at physiological pH, The mass spectra of se quences containing two tyrosine residues showed the formation of both monon itrated and dinitrated species, while those with phenylalanine showed no de tectable nitration. Tryptic digests of two of the investigated peptides wer e also examined by liquid chromatography/electrospray mass spectrometry, wh ich yielded further information on the competition for NO2 by multiple nitr ation sites within a given sequence. In addition, tryptic digests of the mo nonitrated component of sequences containing tyrosine and tryptophan indica ted that mononitration was limited to tyrosine. Furthermore, some of the pr esented data indicate that, as well as nitrotyrosine and nitrotryptophan fo rmation, the reaction of ONOO- cars result in oxidation as well as the form ation of labile adducts with NO2, Copyright (C) 1999 John Wiley & Sons, Ltd .