EPR Study of UV-Irradiated Thymidine Microcrystals Supports Radical Intermediates in Spore Photoproduct Formation
EPR Study of UV-Irradiated Thymidine Microcrystals Supports Radical Intermediates in Spore Photoproduct Formation
复制标题
紫外线照射胸苷微晶的 EPR 研究支持孢子光产物形成中的自由基中间体
DOI：
10.1021/acs.jpcb.6b06587
复制
发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Stoll, Stefan
中科院分区：
文献类型：
--
作者：
Hayes, Ellen C.;Jian, Yajun;Li, Lei;Stoll, Stefan
孢子光产物是细菌内孢子DNA暴露在紫外线(UV)辐射下时形成的胸苷二聚体。这种胸腺嘧啶核苷二聚体的形成机制被认为是通过自由基对中间体进行的。当一个胸苷碱基的甲基氢原子转移到相邻胸苷碱基的C6位时，形成中间体，分别形成两种自由基，TCH2和TH。利用一系列的胸腺嘧啶核苷同位素和电子顺磁共振(EPR)谱，我们证明了紫外线照射下的胸腺嘧啶核苷微晶产生这两种自由基物种。我们观察到了三个来源，它们在TH自由基的C6位置提供了额外的氢。三种来源之一是TH物种中相当一部分的另一种胸腺嘧啶核苷分子的甲基。这支持了孢子光产物形成中提出的自由基对中间体。
Spore photoproduct is a thymidine dimer formed when bacterial endospore DNA is exposed to ultraviolet (UV) radiation. The mechanism of formation of this thymidine dimer has been proposed to proceed through a radical-pair intermediate. The intermediate forms when a methyl-group hydrogen atom of one thymidine nucleobase is transferred to the C6 position of an adjacent thymidine nucleobase, forming two species, the TCH2and TH radicals, respectively. Using a series of thymidine isotopologues and electron paramagnetic resonance (EPR) spectroscopy, we show that microcrystals of thymidine exposed to UV radiation produce these two radical species. We observe three sources that donate the additional hydrogen at the C6 position of the TH radical. One of the three sources is the methyl group of another thymidine molecule in a significant fraction of the TH species. This lends support to the radical-pair intermediate proposed in the formation of spore photoproduct.