FEBS Lett. 1983 Jul 11;158(1):143-6. doi: 10.1016/0014-5793(83)80695-4.
To gain an understanding of the mechanism by which the hydroxyl free radical can arise in superoxide generating systems and learn how different chelaters of iron can inhibit this reaction, a pulse radiolysis kinetic study of the reaction of O;- with Fe(III)EDTA, Fe(III)HEDTA and Fe(III)DETAPAC (or DTPA)was undertaken. Superoxide reacts readily with Fe(III)EDTA and Fe(III)HEDTA with a pH-dependent second-order rate constant having values of 1.9 x lo6 M-l. s-’ and 7.6 x 16 M-‘. s-’ at pH 7,respectively. However, the rate constant for the reaction of O;- with Fe(III)DETAPAC was found to be much slower, the upper limit for the rate constant being 104 M-l. s-l. These results in conjunction with spin-trapping experiments with Fe(II)EDTA, Fe(II)HEDTA, Fe(II)DETAPAC and Hz02 suggests that DETAPAC inhibits the formation of 'OH by slowing the reduction of Fe(II1) to Fe(I1) and not by inhibiting the Fenton reaction.
为了了解超氧自由基在产生超氧自由基的系统中产生的机制，并研究不同的铁螯合剂如何抑制这种反应，我们进行了脉冲辐射动力学研究，研究了 O;-与 Fe(III)EDTA、Fe(III)HEDTA 和 Fe(III)DETAPAC（或 DTPA）的反应。超氧自由基与 Fe(III)EDTA 和 Fe(III)HEDTA 迅速反应，在 pH 值为 7 时，其二级速率常数分别为 1.9 x lo6 M-l. s-’和 7.6 x 16 M-‘. s-’。然而，O;-与 Fe(III)DETAPAC 的反应速率常数要慢得多，其速率常数的上限为 104 M-l. s-l。这些结果与 Fe(II)EDTA、Fe(II)HEDTA、Fe(II)DETAPAC 和 Hz02 的自旋捕获实验一起表明，DETAPAC 通过减缓 Fe(II1)还原为 Fe(I1)来抑制 'OH 的形成，而不是通过抑制 Fenton 反应。
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