One-electron reduction of S-nitrosothiols in aqueous medium

• Published in: Free radical biology & medicine 2006-10, Vol.41 (8), p.1240-1246
• Main Authors: Manoj, V.M., Mohan, H., Aravind, U.K., Aravindakumar, C.T.
• Format: Article
• Language: English
• Subjects: Electrons; Free Radicals - chemistry; Free Radicals - metabolism; Hydrated electron; In Vitro Techniques; Kinetics; N-centered radical; Nitric oxide; Nitric Oxide - metabolism; One-electron reduction; Oxidation-Reduction; Pulse radiolysis; Radiation chemical; Rate constants; S-Nitrosothiols; S-Nitrosothiols - chemistry; S-Nitrosothiols - metabolism; Thiyl radical; Water
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2006.06.025

One-electron reduction of S-nitrosothiols (RSNO) has been studied using radiolytically produced reducing entity, the hydrated electron ( e aq −), in aqueous medium. Both kinetics of the reaction and the mechanistic aspects of the decomposition of S-nitroso derivatives of glutathione, L-cysteine, N-acetyl-L-cysteine, N-acetyl-D,L-penicillamine, N-acetylcysteamine, L-cysteine methyl ester, and D,L-penicillamine have been investigated at neutral and acidic pH. The second-order rate constants of the reaction of e aq − with RSNOs were determined using a pulse radiolysis technique and were found to be diffusion controlled (10 10 dm 3 mol − 1 s − 1 ) at neutral pH. The product analysis using HPLC, fluorimetry, and MS revealed the formation of thiol and nitric oxide as the major end products. It is therefore proposed that one-electron reduction of RSNO leads to the liberation of NO. There is no intermediacy of a thiyl radical as in the case of oxidation reactions of RSNOs. The radical anion of RSNO (RSN O −) is proposed as a possible intermediate. The overall reaction could be written as ▪