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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 2. Carbonate radical anion
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Theoretical and experimental studies of the spin trapping of inorganic radicals by 5,5-dimethyl-1-pyrroline N-oxide (DMPO). 2. Carbonate radical anion

机译：5,5-二甲基-1-吡咯啉N-氧化物（DMPO）自旋俘获无机自由基的理论和实验研究。 2.碳酸根阴离子

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Previous studies have shown that the enzyme-mediated generation of carbonate radical anion (CO3 center dot-) may play an important role in the initiation of oxidative damage in cells. This study explored the thermodynamics of CO3 center dot- addition to 5,5-dimethyl-1-pyrroline N-oxide (DMPO) using density functional theory at the B3LYP/6-31+G**//B3LYP/6-31G* and B3LYP/6-311+G* levels with the polarizable continuum model to simulate the effect of the bulk dielectric effect of water on the calculated energetics. Theoretical data reveal that the addition of CO3 center dot- to DMPO yields an O-centered radical adduct (DMPO-OCO2) as governed by the spin (density) population on the CO3 center dot-. Electron paramagnetic resonance spin trapping with the commonly used spin trap, DMPO, has been employed in the detection of CO3 center dot-. UV photolysis of H2O2 and DMPO in the presence of sodium carbonate (Na2CO3) or sodium bicarbonate (NaHCO3) gave two species (i.e., DMPO-OCO2 and DMPO-OH) in which the former has hyperfine splitting constant values of a(N) = 14.32 G, a(beta-Eta) = 10.68 G, and a(gamma-H) = 1.37 G and with a shorter half-life compared to DMPO-OH. The origin of the DMPO-OH formed was experimentally confirmed using isotopically enriched (H2O2)-O-17 that indicates direct addition of HO center dot to DMPO. Theoretical studies on other possible pathways for the formation of DMPO-OH from DMPO-OCO2 in aqueous solution and in the absence of free HO center dot such as in the case of enzymatically generated CO3 center dot-, show that the preferred pathway is via nucleophilc substitution of the carbonate moiety by H2O or HO-. Nitrite formation has been observed as the end product of CO3 center dot- trapping by DMPO and is partly dependent on the basicity of solution. The thermodynamic behavior of CO3 center dot- in the aqueous phase is predicted to be similar to that of the hydroperoxyl (HO2 center dot) radical.
机译：先前的研究表明，酶介导的碳酸根阴离子（CO3中心点）的产生可能在细胞氧化损伤的引发中起重要作用。这项研究使用密度泛函理论在B3LYP / 6-31 + G ** // B3LYP / 6-31G *上探索了向5,5,5-二甲基-1-吡咯啉N-氧化物（DMPO）添加CO3中心点的热力学*和B3LYP / 6-311 + G *水平与可极化连续体模型一起模拟水的整体介电效应对计算出的高能学的影响。理论数据表明，向DMPO中添加CO3中心点可产生O中心自由基加合物（DMPO-OCO2），该自由基加合物受CO3中心点上的自旋（密度）族支配。常用的自旋阱DMPO的电子顺磁共振自旋阱已用于检测CO3中心点。在碳酸钠（Na2CO3）或碳酸氢钠（NaHCO3）存在下，H2O2和DMPO的紫外线光解产生两种物质（即DMPO-OCO2和DMPO-OH），其中前者具有超精细的分裂常数a（N）=与DMPO-OH相比，其具有14.32 G，a（β-Eta）= 10.68 G和a（γ-H）= 1.37 G的半衰期。使用同位素富集的（H2O2）-O-17通过实验证实了所形成的DMPO-OH的起源，这表明HO中心点直接添加到DMPO中。对水溶液中DMPO-OCO2由DMPO-OCO2形成DMPO-OH的其他可能途径的理论研究，例如在酶促生成的CO3中心点-的情况下，表明优选的途径是通过亲核试剂碳酸根部分被H2O或HO-取代。已观察到亚硝酸盐的形成是DMPO捕获CO3中心点的最终产物，部分取决于溶液的碱性。预测水相中CO3中心点的热力学行为与氢过氧基（HO2中心点）的热力学行为相似。

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