title: Decomposition kinetics of peroxynitrite: influence of pH and buffer.
abstract: The decay of ONOOH near neutral pH has been examined as a function of isomerization to H(+) and NO3(-), and decomposition to NO2(-) and O2via O2NOO(-). We find that in phosphate buffer k(isomerization) = 1.11 ± 0.01 s(-1) and k(disproportionation) = (1.3 ± 0.1) × 10(3) M(-1) s(-1) at 25 °C and I = 0.2 M. In the presence of 0.1 M tris(hydroxymethyl)aminomethane (Tris), the decay proceeds more rapidly: k(disproportionation) = 9 × 10(3) M(-1) s(-1). The measured first half-life of the absorbance of peroxynitrite correlates with [Tris]0·([ONOO(-)]0 + [ONOOH]0)(2), where the subscript 0 indicates initial concentrations; if this function exceeds 6.3 × 10(-12) M(3), then Tris significantly accelerates the decomposition of peroxynitrite.
authors.affiliation: Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Molina
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kissner
authors.forename: Willem H
authors.initials: WH
authors.lastname: Koppenol
mesh_terms: D002021:Buffers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D030421:Peroxynitrous Acid / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*
chemical_list: D002021:Buffers; D010710:Phosphates; D030421:Peroxynitrous Acid