Decomposition kinetics of peroxynitrite: Influence of pH and buffer

摘要

The decay of ONOOH near neutral pH has been examined as a function of isomerization to H~+ and NO_3 ~-, and decomposition to NO_2 ~- and O_2via O_2NOO ~-. 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. This journal is