REDUCTION AND DESTRUCTION RATES OF NITROXIDE SPIN PROBES
REDUCTION AND DESTRUCTION RATES OF NITROXIDE SPIN PROBES
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DOI：
10.1016/0003-9861(87)90441-3
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发表时间：
1987-07-01
影响因子：
3.9
通讯作者：
PACKER, L
中科院分区：
文献类型：
--
作者：
BELKIN, S;MEHLHORN, RJ;PACKER, L
用ESR法测定了一系列氮氧化物在一种化学体系、一种光化学体系和两种生物体系中的单电子还原速率。在所有情况下，哌啶和氢吡啶的氮氧化物比吡咯和吡咯烷的氮氧化物更迅速地持续地被还原。氮氧化物上的取代基也会影响还原速率，尽管没有环结构那么大。其中一种由光敏剂FMN和光还原剂EDTA组成的还原体系用于研究某些氮氧化物的厌氧还原和依赖于o2的再氧化。还原后的吡啶和氢吡啶氮氧化物也比还原后的吡啶和吡咯烷氮氧化物氧化得更快。还原后的再氧化被超氧化物歧化酶部分抑制，表明超氧化物自由基参与了这一过程。即使经过长时间的再氧化，也不是所有的探针分子都恢复到氧化状态，这意味着自旋探针在化学还原的同时发生了不可逆的“破坏”。利用光化学系统更具体地研究了探针破坏生成甲基自由基，结果表明这些碳中心自由基破坏不同氮氧化物的速率比单电子还原受氮氧化物结构的影响要小得多。
A series of nitroxides was tested for rates of one-electron reduction in a chemical, a photochemical, and two biological systems by ESR assays. In all cases, piperidine and hydropyridine nitroxides were reduced consistently more rapidly than pyrroline and pyrrolidine nitroxides. Substituents on the nitroxides also affected reduction rates, although not as greatly as ring structure. One of the reduction systems, consisting of the photosensitizer FMN and the photoreductant EDTA, was used to study both anaerobic reduction and O2-dependent reoxidation of some of the nitroxides. Reduced piperidine and hydropyridine nitroxides were also oxidied more rapidly than the reduced pyrroline and pyrrolidine nitroxides. Reoxidation subsequent to reduction was partially inhibited by superoxide dismutase, indicating that superoxide radicals are involved in the process. Even after prolonged reoxidation, not all of the probe molecules were returned to their oxidized form, implying an irreversible "destruction" of the spin probe concomitant with its chemical reduction. Probe destruction was studied more specifically with a photochemical system for generating methyl radicals, which showed that these carbon-centered radicals destroyed different nitroxides at rates which were much less influenced by the nitroxide structures than one-electron reduction was.