Reactions of manganese Porphyrins with peroxynitrite and carbonate radical anion
Reactions of manganese Porphyrins with peroxynitrite and carbonate radical anion
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DOI：
10.1074/jbc.m213302200
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发表时间：
2003-07-25
影响因子：
4.8
通讯作者：
Radi, R
中科院分区：
文献类型：
--
作者：
Ferrer-Sueta, G;Vitturi, D;Radi, R
我们研究了十种不同中位取代基的锰卟啉与过氧亚硝酸盐（ONOO-）和碳酸盐自由基阴离子（CO3----）的反应动力学，分别采用停流和脉冲辐射分解。Mn（III）卟啉与ONOO-反应的速率常数范围为1 × 10(5)至3.4 × 10(7) M-1 s(-1)，与先前报道的反映取代基在卟啉环上的共振和感应效应的动力学和热力学数据具有良好的相关性。Mn（III）卟啉与CO3反应的速率常数----。在pH小于或等于8.5时，其范围从2 × 10(8)到1.2 × 10(9) m - 1s(-1)，并且由于配合物的电离而随着pH的增加而增加。Mn（II）卟啉与CO3反应----。在pH 10.4下，速率常数范围为1 × 10(9)至5 × 10(9) M-1 s（-1）。因此，快速清除ONOO-和CO3----。由于锰卟啉可以在体内发生催化还原，而牺牲了许多细胞还原剂。此外，我们用分光光度滴定法测定了pH值为7.5 ~ 13.2的Mn（III）配合物的轴向水分子的pK（α）。研究结果与大多数配合物的两种酸碱平衡相一致。pK（α）值也与取代基的共振效应和感应效应相关。当n -烷基吡啶取代基包含比乙基长的n -烷基基团时，E-1/2与ONOO-速率常数和pK（α）值的相关性偏离线性，这可以解释为局部介电常数的降低。
We have studied the reaction kinetics of ten manganese porphyrins, differing in their meso substituents, with peroxynitrite (ONOO-) and carbonate radical anion (CO3----) using stopped-flow and pulse radiolysis, respectively. Rate constants for the reactions of Mn(III) porphyrins with ONOO- ranged from 1 X 10(5) to 3.4 X 10(7) M-1 s(-1) and correlated well with previously reported kinetic and thermodynamic data that reflect the resonance and inductive effects of the substituents on the porphyrin ring. Rate constants for the reactions of Mn(III) porphyrins with CO3----. ranged from 2 X 10(8) to 1.2 X 10(9) M-1 s(-1) at pH less than or equal to 8.5 and increased with pH as a consequence of the ionization of the complexes. Mn(II) porphyrins reacted with CO3----. with rate constants ranging from 1 X 10(9) to 5 X 10(9) M-1 s(-1) at pH 10.4. Hence, fast scavenging of ONOO- and CO3----. by manganese porphyrins could occur in vivo because of the catalytic reduction at the expense of a number of cellular reductants. Additionally, we determined the pK(alpha) of the axial water molecules of the Mn(III) complexes at pH 7.5-13.2 by spectrophotometric titration. Results were consistent with two acid-base equilibria for most of the complexes studied. The pK(alpha) values also correlated with the resonance and inductive effects of the substituents. The correlations of E-1/2 with the rate constants with ONOO- and with the pK(alpha) values display a deviation from linearity when N-alkylpyridinium substituents included N-alkyl moieties longer than ethyl, which is interpreted in terms of a decrease in the local dielectric constant.