5,5-二甲基-1-吡咯啉<i>N-</i>氧化物（DMPO）超氧化物自旋加合物的EPR光谱分配<a aria-label="†" href="#jo048518zAF2">†</a>,The Journal of Organic Chemistry

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5,5-二甲基-1-吡咯啉N-氧化物（DMPO）超氧化物自旋加合物的EPR光谱分配 †
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2005-01-13 00:00:00 , DOI: 10.1021/jo048518z
Jean-Louis Clément ₁ , Nicolas Ferré ₁ , Didier Siri ₁ , Hakim Karoui ₁ , Antal Rockenbauer ₁ , Paul Tordo ₁

Affiliation

自旋捕集包括使用硝酮或亚硝基化合物“捕集”不稳定的自由基作为长寿命的氮氧化物，其特征可通过电子顺磁共振（EPR）光谱进行表征。DMPO-OOH的形成是通过用5,5-二甲基-1-吡咯啉N-氧化物（DMPO）捕获超氧化物（O ₂^•^-）而产生的自旋加合物，已被用于检测多种形式的超氧化物的生成生物和化学系统。DMPO-OOH的12线EPR光谱已在一千多篇论文中进行了报道或提及。它已被解释为来自以下联轴器所得：甲_Ñ ≃1.42 mT的甲_ħ^_β＆cong; 1.134 mT的，和甲_ħ^_γ（1H）≃0.125 mT。但是，DMPO-OOH EPR频谱具有不对称性，当考虑单个物种时，该频谱无法重现。最近，有人提出0.125 mT的分裂是错误分配的，实际上是由与DMPO-OOH不同构象体有关的两个单独的EPR光谱的叠加引起的。我们已经制备了5,5-二甲基-[3,3-² H₂ ] -1-吡咯啉N-氧化物（DMPO- d ₂），我们发现相应的超氧化物自旋加合物的EPR谱仅由6条线组成，这与将0.125 mT拆分指定为从与DMPO碳3键合的氢原子进行γ拆分的分配一致。该结果得到包括水溶作用在内的DFT计算的支持，并且假设两个构象异构体之间进行了化学交换，则很好地再现了DMPO-OOH EPR光谱的不对称性。

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Assignment of the EPR Spectrum of 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO) Superoxide Spin Adduct†

Spin trapping consists of using a nitrone or a nitroso compound to “trap” an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO−OOH, the spin adduct resulting from trapping superoxide (O₂^•^-) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO−OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: A_N ≃ 1.42 mT, A_H^_β ≃ 1.134 mT, and A_H^_γ (1H) ≃ 0.125 mT. However, the DMPO−OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO−OOH. We have prepared 5,5-dimethyl-[3,3-²H₂]-1-pyrroline N-oxide (DMPO-d₂), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a γ-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO−OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.

更新日期：2005-01-13

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