Reszka K, Bilski P, Chignell C F
Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709.
Free Radic Res Commun. 1992;17(6):377-85. doi: 10.3109/10715769209083142.
Electron spin resonance spectroscopy and the spin trapping technique were used to study the formation of the superoxide radical in pyridine. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was employed as a trapping agent. Superoxide radical was generated using chemical (potassium superoxide) and photochemical methods with anthralin, benzanthrone, rose bengal, 1,8-dihydroxyanthraquinone and zinc tetraphenylporphyrine as photoactive pigments. Hyperfine coupling (hf) constants for DMPO/O2.- were determined to be aN = 12.36 G, a beta H = 9.85, G, a gamma H = 1.34 G. The aN and a beta H hf constants are in good agreement with values calculated from a previously determined relationship between hf constants and solvent acceptor number (Reszka et al., (1992) Free Radical Res. Commun., in press). When concentrated hydrogen peroxide was added to DMPO in pyridine a similar EPR spectrum was observed. It is suggested that in this case the DMPO/.O2H adduct is formed by nucleophilic addition of H2O2 to DMPO to give a hydroxylamine, followed by oxidation to the respective nitroxide. The EPR spectrum observed when tetrapropylammonium hydroxide and H2O2 were added to DMPO in pyridine had hf couplings aN = 13.53 G, a beta H = 11.38 G, a gamma H = 0.79 G and it was assigned to a DMPO/.OH adduct. This assignment was based on similarity of this spectrum to the one produced by UV photolysis of hydrogen peroxide and DMPO in aqueous solution and subsequent transfer to pyridine.
采用电子自旋共振光谱法和自旋捕集技术研究了吡啶中超氧自由基的形成。5,5 - 二甲基 - 1 - 吡咯啉 - N - 氧化物（DMPO）用作捕集剂。使用化学方法（超氧化钾）和光化学方法，以蒽林、苯并蒽酮、孟加拉玫瑰红、1,8 - 二羟基蒽醌和四苯基卟啉锌作为光活性色素来产生超氧自由基。测定了DMPO/O₂⁻的超精细偶合（hf）常数，其中aN = 12.36 G，aβH = 9.85 G，aγH = 1.34 G。aN和aβH hf常数与根据先前确定的hf常数和溶剂受体数之间的关系计算得到的值非常吻合（Reszka等人，（1992年）《自由基研究通讯》，即将发表）。当向吡啶中的DMPO加入浓过氧化氢时，可以观察到类似的电子顺磁共振光谱。据推测，在这种情况下，DMPO/.O₂H加合物是由H₂O₂对DMPO进行亲核加成生成羟胺，然后氧化为相应的氮氧化物而形成的。当将氢氧化四丙铵和H₂O₂加入吡啶中的DMPO时观察到的电子顺磁共振光谱，其hf偶合为aN = 13.53 G，aβH = 11.38 G，aγH = 0.79 G，该光谱被归属于DMPO/.OH加合物。这一归属是基于该光谱与过氧化氢和DMPO在水溶液中紫外光解后转移至吡啶所产生的光谱的相似性。
