ESR spin-trapping studies on the reaction of Fe2+ ions with H2O2-reactive species in oxygen toxicity in biology.
ESR spin-trapping studies on the reaction of Fe2+ ions with H2O2-reactive species in oxygen toxicity in biology.
复制标题
DOI：
10.1016/s0021-9258(18)77389-4
复制
发表时间：
1990-08
期刊：
影响因子：
--
通讯作者：
I. Yamazaki;L. Piette
中科院分区：
文献类型：
--
作者：
I. Yamazaki;L. Piette
利用5，5-二甲基-1-吡咯啉-N-氧化物（DMPO）的ESR自旋捕获技术，在[H_2O_2]为90 μ M，[Fe ~（2+）]为1 μ M或更低的实验条件下，证实了在芬顿反应中羟基自由基与Fe ~（2+）形成的化学计量比为1：1，随着Fe ~（2+）浓度的增加，化学计量比显著降低。羟基自由基产生的效率随所使用的铁螯合剂的性质而变化，并且以单独磷酸盐的顺序增加，大约ADP小于EDTA小于二亚乙基三胺五乙酸（EDTA PAC）。测得单独磷酸盐的芬顿反应二级速率常数为2.0 x 10（4）M-1 s-1，ADP为8.2 x 10（3）M-1 s-1，EDTA为1.4 x 10（4）M-1 s-1，DETAPAC为4.1 x 10（2）M-1 s-1。测量自由基形成的自旋被困在乙醇的存在下，我们估计的总氧化中间体形成的芬顿反应，我们得出的结论是由羟基自由基和铁物种的量。在ADP存在下，即使在低Fe 2+浓度下，也能有效地产生铁的氧化物种，其可能被分配为ferryl，FeO 2+，或Fe（IV）= O。在一般情况下，作为Fe 2+浓度增加，铁物种占主导地位的羟基自由基的情况下，除了Fe（II）-dopamine PAC，它只产生羟基自由基作为氧化物种。三种可能的途径提出了芬顿反应，占主导地位的非常依赖于所使用的铁螯合剂的性质。
Using ESR spin-trapping techniques with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), we confirmed the 1:1 stoichiometry for the formation of hydroxyl radicals with Fe2+ in the Fenton reaction under experimental conditions wherein [H2O2] is 90 microM and [Fe2+] is very low, 1 microM or less. The stoichiometry decreased markedly as the Fe2+ concentration was increased. The efficiency of hydroxyl radical generation varied with the nature of the iron chelators used and increased in the order of phosphate alone approximately ADP less than EDTA less than diethylenetriaminepentaacetic acid (DETAPAC). The second order rate constant for the Fenton reaction was measured to be 2.0 x 10(4) M-1 s-1 for phosphate alone, 8.2 x 10(3) M-1 s-1 for ADP, 1.4 x 10(4) M-1 s-1 for EDTA, and 4.1 x 10(2) M-1 s-1 for DETAPAC. Measuring the radicals formed as spins trapped in the presence of ethanol, we estimated the amount of total oxidizing intermediates formed in the Fenton reaction, which we concluded consists of hydroxyl radicals and an iron species. The oxidizing species of iron which might be assigned as ferryl, FeO2+, or Fe(IV) = O was generated effectively in the presence of ADP even at low Fe2+ concentrations. In general, as the Fe2+ concentration was increased, the ferryl species predominated over the hydroxyl radical except for the case of Fe(II)-DETAPAC, which generated only hydroxyl radicals as the oxidizing species. Three possible pathways are proposed for the Fenton reaction, the dominant ones depending very much on the nature of the iron chelator being used.