Electrospray ionization mass spectrometry of low-molecular-mass S-nitroso compounds and their thiols

Low-molecular-mass S-nitroso compounds (R-S-N=O) are potent vasodilators an d inhibitors of platelet aggregation. This work describes the electrospray ionization mass spectrometric (ESI-MS) analysis of physiological and synthe tic low-molecular-mass S-nitroso compounds and their thiols including S-nit rosoglutathione, S-nitrosocysteine, glutathione and cysteine. Mass spectra of the unlabeled and S-'5N-labeled low-molecular-mass S-nitroso compounds i nvestigated are characterized by abundant cations due to [M+H](+), [M+Na](), [(M+H)-NO](+), [2 M+H](+), and [(2 M+H)-2NO](+). Mass spectra of low-mol ecular-mass thiols are characterized by abundant cations due to [M+H](+), [ M+Na](+) and [2M+H](+). Using off-line electrospray ionization tandem mass spectrometry we unequivocally identified S-[N-15]nitrosoglutathione in huma n red blood cells formed after their incubation with S-[N-15]nitrosocystein e. These results suggest that ESI-MS in combination with an appropriate liq uid chromatographic system should be a useful analytical approach for the o n-line quantitative determination of low-molecular-mass S-nitroso compounds in biological fluids in the presence of their thiols and nitrite. Consider ations were made about on-line ESI-MS and quantitative measurements. (C) 20 00 Elsevier Science B.V. All rights reserved.