Figure 8. pH dependence of the second-order rate constant for the Ma-Pgb-Fe(III)-mediated peroxynitrite isomerization (h app; panel A) and of the first-order rate constant for the spontaneous isomerization of peroxynitrite to nitrate (h 0; panel B), at 20°C.
The continuous line in panel A was calculated according to Eq. 6 with pK a = 6.7, h app(prot) = 1.7×105 M−1 s−1, and h app(unprot) = 5.1×103 M−1 s−1. The continuous line in panel B was calculated according to Eq. 6 with pK a = 6.9, h 0(prot) = 8.2×10−1 s−1, and h 0(unprot) = 8.6×10–3 s−1. Where not shown, the standard deviation is smaller than the symbol. For details, see text.