title: Insights into the mechanism of the reaction between hydrogen sulfide and peroxynitrite.
abstract: Hydrogen sulfide and peroxynitrite are endogenously generated molecules that participate in biologically relevant pathways. A revision of the kinetic features of the reaction between peroxynitrite and hydrogen sulfide revealed a complex process. The rate constant of peroxynitrite decay, (6.65 ± 0.08) × 10(3) M(-1) s(-1) in 0.05 M sodium phosphate buffer (pH 7.4, 37°C), was affected by the concentration of buffer. Theoretical modeling suggested that, as in the case of thiols, the reaction is initiated by the nucleophilic attack of HS(-) on the peroxide group of ONOOH by a typical bimolecular nucleophilic substitution, yielding HSOH and NO2(-). In contrast to thiols, the reaction then proceeds to the formation of distinct products that absorb near 408 nm. Experiments in the presence of scavengers and carbon dioxide showed that free radicals are unlikely to be involved in the formation of these products. The results are consistent with product formation involving the reactive intermediate HSSH and its fast reaction with a second peroxynitrite molecule. Mass spectrometry and UV-Vis absorption spectra predictions suggest that at least one of the products is HSNO2 or its isomer HSONO.
authors.affiliation: Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, 11400 Montevideo, Uruguay; Center for Free Radical and Biomedical Research, Universidad de la República, 11800 Montevideo, Uruguay.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Cuevasanta
authors.affiliation: Departamento de Química Inorgánica, Analítica, y Química-Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA Buenos Aires, Argentina.
authors.forename: Ari
authors.initials: A
authors.lastname: Zeida
authors.affiliation: Center for Free Radical and Biomedical Research, Universidad de la República, 11800 Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, 11800 Montevideo, Uruguay.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Carballal
authors.affiliation: Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Wedmann
authors.affiliation: Departamento de Química Inorgánica, Analítica, y Química-Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA Buenos Aires, Argentina.
authors.forename: Uriel N
authors.initials: UN
authors.lastname: Morzan
authors.affiliation: Center for Free Radical and Biomedical Research, Universidad de la República, 11800 Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, 11800 Montevideo, Uruguay.
authors.forename: Madia
authors.initials: M
authors.lastname: Trujillo
authors.affiliation: Center for Free Radical and Biomedical Research, Universidad de la República, 11800 Montevideo, Uruguay; Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, 11800 Montevideo, Uruguay.
authors.forename: Rafael
authors.initials: R
authors.lastname: Radi
authors.affiliation: Departamento de Química Inorgánica, Analítica, y Química-Física and INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA Buenos Aires, Argentina.
authors.forename: Darío A
authors.initials: DA
authors.lastname: Estrin
authors.affiliation: Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, 91058 Erlangen, Germany. Electronic address: milos.filipovic@fau.de.
authors.forename: Milos R
authors.initials: MR
authors.lastname: Filipovic
authors.affiliation: Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, 11400 Montevideo, Uruguay; Center for Free Radical and Biomedical Research, Universidad de la República, 11800 Montevideo, Uruguay. Electronic address: beatriz.alvarez@fcien.edu.uy.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Alvarez
mesh_terms: D002021:Buffers; D006862:Hydrogen Sulfide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D030421:Peroxynitrous Acid / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002021:Buffers; D013440:Sulfides; C051552:persulfides; D030421:Peroxynitrous Acid; D006862:Hydrogen Sulfide
keywords: Free radicals; Hydrogen sulfide; Kinetics; Peroxynitrite; Persulfides