Kondo T, Krishna C M, Riesz P
Radiation Oncology Branch, National Cancer Institute, Bethesda, Maryland 20892.
Int J Radiat Biol Relat Stud Phys Chem Med. 1988 Feb;53(2):331-42. doi: 10.1080/09553008814550681.
Direct evidence for the detection of intermediate radicals of nucleic acid constituents induced by ultrasound in argon-saturated aqueous solution is presented. The method of spin trapping with 3,5-dibromo-4-nitrosobenzene sulphonate, which is a water-soluble, non-volatile, aromatic nitroso spin trap, combined with ESR, was used for the detection of sonochemically induced radicals. Spin adducts were also generated by OH radicals produced by UV photolysis of aqueous solution containing H2O2. ESR spectra observed from these photolysis experiments were identical to those after sonolysis. The ESR spectra of the spin adducts suggest that the major spin-trapped radical of thymine and thymidine was the 5-yl radical, and that of cytosine, cytidine, uracil, and uridine was the 6-yl radical. To compare the radicals induced by sonolysis and photolysis, the decay of the ESR spectra of the thymine and thymidine spin adducts was investigated. The decay curves of thymine and thymidine after sonolysis indicated biphasic decay. However, after photolysis the spin adducts from both compounds showed very little decay. These results suggest that the observed spin adducts in the sonolysis of pyrimidine bases and nucleosides were formed by OH radical and H atom addition to the 5,6 double-bond.
本文提供了在氩气饱和水溶液中超声诱导核酸成分中间自由基检测的直接证据。使用3,5-二溴-4-亚硝基苯磺酸盐（一种水溶性、非挥发性的芳香亚硝基自旋捕集剂）与电子自旋共振（ESR）相结合的自旋捕集方法来检测声化学诱导的自由基。含有过氧化氢的水溶液经紫外光解产生的羟基自由基也能生成自旋加合物。从这些光解实验中观察到的ESR光谱与声解后的光谱相同。自旋加合物的ESR光谱表明，胸腺嘧啶和胸腺嘧啶核苷的主要自旋捕集自由基是5-基自由基，而胞嘧啶、胞嘧啶核苷、尿嘧啶和尿苷的主要自旋捕集自由基是6-基自由基。为了比较声解和光解诱导的自由基，研究了胸腺嘧啶和胸腺嘧啶核苷自旋加合物的ESR光谱衰减情况。声解后胸腺嘧啶和胸腺嘧啶核苷的衰减曲线呈双相衰减。然而，光解后两种化合物的自旋加合物几乎没有衰减。这些结果表明，嘧啶碱基和核苷声解过程中观察到的自旋加合物是由羟基自由基和氢原子加成到5,6-双键上形成的。
