Selective trapping of SNO-BSA and GSNO by benzenesulfinic acid sodium salt: mechanistic study of thiosulfonate formation and feasibility as a protein S-nitrosothiol detection strategy

Abstract The conversion of S -nitrosothiols to thiosulfonates by reaction with the sodium salt of benzenesulfinic acid (PhSO 2 Na) has been examined in detail with the exemplary substrates S -nitrosoglutathione (GSNO) and S -nitrosylated bovine serum albumin (SNO-BSA). The reaction stoichiometry (2:1, PhSO 2 Na:RSNO) and the rate law (first order in both PhSO 2 Na and RSNO) have been determined under mild acidic conditions (pH 4.0). The products have been identified as the corresponding thiosulfonates (GSSO 2 Ph and BSA-SSO 2 Ph) along with PhSO 2 NHOH obtained in a 1:1 ratio. GSH, GSSG, and BSA were unreactive to PhSO 2 Na.