EPR characterization of ascorbyl and sulfur dioxide anion radicals trapped during the reaction of bovine Cytochrome c Oxidase with molecular oxygen.
EPR characterization of ascorbyl and sulfur dioxide anion radicals trapped during the reaction of bovine Cytochrome c Oxidase with molecular oxygen.
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DOI：
10.1016/j.jmr.2009.12.017
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发表时间：
2010-04
期刊：
影响因子：
--
通讯作者：
Gerfen GJ
中科院分区：
文献类型：
--
作者：
Yu MA;Egawa T;Yeh SR;Rousseau DL;Gerfen GJ
用冷冻猝灭法捕获了还原态牛细胞色素c氧化酶（CcO）与氧在50 μs ~ 6 msec反应的中间产物，并用EPR研究了其性质。当用抗坏血酸盐或连二亚硫酸盐还原酶时，会产生不同的自由基; X波段（9 GHz）和D波段（130 GHz）的CWEPR测量支持这些自由基分别归属于抗坏血酸盐和二氧化硫阴离子自由基（SO 2−·）。X波段光谱显示抗坏血酸自由基的线宽为12 G，SO 2−·自由基的线宽为11 G，两种物质的各向同性g值均为2.005。D-带光谱揭示了两个物种的g-张量和粉末图案的明显区别。抗坏血酸自由基光谱显示出近似轴对称性，g值为gx = 2.0068，戈伊= 2.0066和gz = 2.0023。SO 2 −·自由基具有菱形对称性，g值为gx = 2.0089，戈伊= 2.0052，gz = 2.0017。当去除抗坏血酸和SO2−·自由基的贡献时，在EPR光谱中无法识别CcO上的蛋白质基。
The reaction intermediates of reduced bovine Cytochrome c Oxidase (CcO) were trapped following its reaction with oxygen at 50 μs to 6 msec by innovative freeze-quenching methods and studied by EPR. When the enzyme was reduced with either ascorbate or dithionite, distinct radicals were generated; X-band (9 GHz) and D-band (130 GHz) CWEPR measurements support the assignments of these radicals to ascorbyl and sulfur dioxide anion radical (SO 2−•) respectively. The X-band spectra show a linewidth of 12 G for the ascorbyl radical and 11 G for the SO 2−• radical and an isotropic g-value of 2.005 for both species. The D-band spectra reveal clear distinctions in the g-tensors and powder patterns of the two species. The ascorbyl radical spectrum displays approximate axial symmetry with g-values of gx = 2.0068, gy = 2.0066, and gz = 2.0023. The SO2−• radical has rhombic symmetry with g-values of gx = 2.0089, gy = 2.0052, and gz = 2.0017. When the contributions from the ascorbyl and SO2−• radicals were removed, no protein-based radical on CcO could be identified in the EPR spectra.
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