87 - Characterization of unique products in reactions of GSNO with H2S

Abstract

The interplay between NO and H2S signaling has attracted much interest in redox proteomics of nitrosative and oxidative stress. Both small molecules appear to target similar pathways in organisms, by reacting with protein free thiols or metalloenzymes to alter or enhance function. We have previously investigated the N-based product speciation in the reaction of GSNO with H2S, specifically noting that the N-based gas product distributions are analogous to those of reactions of GSNO with reductants (e.g. ascorbic acid). We have also identified a plethora of unique glutathione-based products by LC-HRMS analysis. Single Ion Chromatograms (SICs) confirm that these species are present in the reaction mixture and are separated on the LC column prior to ionization. A number of small reactive thiols can be trapped with iodoacetamide (IA), including polysulfides (SnH2), glutathione polysulfides (GSSnH) and trithionitrates, GSN(SnH)2. Unusual trithionitrates are also observed as acetamide adducts, GSN(SnA)2, but only at low ratios of H2S to GSNO. Competition experiments suggest one initial product, the sulfenic acid GSOH, acts as precursor to persulfide and oxidized glutathione-based products. Addition of a non-electrophilic radical trap, vinyl cyclopropane, has little effect on the product distributions, suggesting radical intermediates are short-lived. Other unique dimedone adducts were observed that are attributable to the sulfinyl (GS(O)H) tautomer. We also observe small S-oxoacids, HSOH and S(OH)2, as the derivatized ISnD and DSnD adducts. As with GSOH, unique thioacetals are observed which derive from the sulfenyl tautomers of both HS(O)H and GS(O)H. These unique mixed-valence sulfides have little precedent in the literature but remain observable in reaction mixtures after many hours on the bench.