Behrens G, Koltzenburg G, Ritter A, Schulte-Frohlinde D
Int J Radiat Biol Relat Stud Phys Chem Med. 1978 Feb;33(2):163-71. doi: 10.1080/09553007814550051.
The e.s.r. spectra of 1-yl, 2-yl and 3'-yl methoxyethyl phosphate radicals derived from CH3OCH2CH2-OPO3H2 by hydrogen abstraction have been measured in aqueous solutions and the hyperfine constants determined. The coupling constants vary strongly with protonation or alkylation of the phosphate group. The 2-yl radicals eliminate phosphate. The rate-constants for the elimination (ke) have been estimated by e.s.r. measurements and by product studies as a function of pH using 60Co gamma-radiolysis. The ke values vary from approximately 0.3 s(-1) for the CH3OCHCH2OPO3--radical and approximately 10(3) s-1 for CH3OCHCH2OPO3H-, to approximately 3 X 10(6) S-1 for CH3OCHCH2OPO3H2. Alkylation of the phosphate group increases the elimination rate-constant to a similar extent as protonation. The results support a recent mechanism which described the OH-radical-induced single-strand breaks of DNA in aqueous solution starting from the C-4' radical of the sugar moiety. It is further concluded the C-4' radical of DNA eliminates the 3'-phosphate group faster than the 5'-phosphate group.
通过氢提取从CH3OCH2CH2 - OPO3H2衍生出的1 - 基、2 - 基和3'- 基甲氧基乙基磷酸根自由基的电子自旋共振（e.s.r.）光谱已在水溶液中进行了测量，并确定了超精细常数。耦合常数随磷酸基团的质子化或烷基化而强烈变化。2 - 基自由基会消除磷酸根。消除反应的速率常数（ke）已通过e.s.r.测量以及使用60Coγ辐射分解作为pH函数的产物研究进行了估算。ke值从CH3OCHCH2OPO3--自由基的约0.3 s(-1)、CH3OCHCH2OPO3H-的约10(3) s-1到CH3OCHCH2OPO3H2的约3×10(6) S-1不等。磷酸基团的烷基化使消除速率常数增加的程度与质子化相似。这些结果支持了一种最近的机制，该机制描述了在水溶液中从糖部分的C - 4'自由基开始的OH自由基诱导的DNA单链断裂。进一步得出结论，DNA的C - 4'自由基消除3'-磷酸基团的速度比5'-磷酸基团快。
