Schulte-Frohlinde D, Behrens G, Onal A
Int J Radiat Biol Relat Stud Phys Chem Med. 1986 Jul;50(1):103-10. doi: 10.1080/09553008614550481.
Peroxyl radicals of poly(U), poly(A), and single- and double-stranded DNA have been produced by photolysing H2O2 in oxygenated aqueous solution in presence of the substrates. The peroxyl radicals are formed by the reaction of OH radicals with the polynucleotides followed by addition of oxygen. The lifetime of the peroxyl radicals and the rate constant of their reactions with the thiols cysteamine, glutathione and dithiothreithol have been measured by time-resolved e.s.r. spectroscopy. The unusually long lifetimes range from 0.2 to 3.3 s. The activation energy for the decay for all four substrates is 10.3 +/- 1 kcal/mol (43 kJ mol-1). The reaction rate constants with the thiols range from k = 0.8 X 10(4) to 1.3 X 10(5) dm3 mol-1 s-1. The reactions of the thiols with the peroxyl radical of poly(U) are known to prevent strand break formation. This shows that the peroxyl radicals of poly(U) observed by e.s.r. are intermediates in the pathway leading to strand break formation.
在底物存在的情况下，通过在含氧水溶液中光解过氧化氢，产生了聚尿苷酸（poly(U)）、聚腺苷酸（poly(A)）以及单链和双链DNA的过氧自由基。过氧自由基是由羟基自由基与多核苷酸反应，随后添加氧气形成的。过氧自由基的寿命以及它们与硫醇半胱胺、谷胱甘肽和二硫苏糖醇反应的速率常数已通过时间分辨电子自旋共振光谱法进行了测量。其异常长的寿命范围为0.2至3.3秒。所有四种底物衰变的活化能为10.3±1千卡/摩尔（43千焦/摩尔）。与硫醇的反应速率常数范围为k = 0.8×10⁴至1.3×10⁵立方分米/摩尔·秒⁻¹。已知硫醇与聚尿苷酸的过氧自由基反应可防止链断裂的形成。这表明通过电子自旋共振观察到 的聚尿苷酸过氧自由基是导致链断裂形成途径中的中间体。
