Mechanistic Studies on the Photooxidation of Methylated Cytosine in DNA and Its Application to Novel DNA Methylation Analysis

我们的兴趣集中在5-甲基胞嘧啶(^MC)显著的光氧化活性在甲基化映射系统中的潜在应用，以及进一步了解DNA中^MC的光氧化机制。在该项目中，我们揭示了(1)在DNA链中掺入一个AQ(AQ)增敏剂增强了单电子光氧化，导致了在MC位点的有效的链断裂，(2)中间体MC自由基的C5-甲基上的去质子化可能是在MC处的AQ-光氧化断裂的关键基元反应，以及(3)在多个MC残基上的DNA链断裂是由AQ光注入的正电荷(空穴)通过DNA双链转移而引起的。所得结果可为高灵敏、高选择性光化学方法的分子设计提供指导，用于DNA中MC的鉴定和分析。

Our interest focuses on the potential application of remarkable photooxidative reactivity of 5-methylcytosine (^mC) to methylation-mapping system and on further understanding the mechanism of photooxidation at ^mC in DNA. In the project, we revealed that (1) incorporation of an anthraquinone (AQ) sensitizer into a DNA strand enhanced one-electron photooxidation, leading to efficient strand cleavage at the ^mC site, (2) deprotonation at the C5-methyl group of an intermediate ^mC radical cation may occur as a key elementary reaction in the AQ-photooxidative strand cleavage at the ^mC, and (3) DNA strand cleavage at multiple ^mC residues was induced by AQ-photoinjected positive charge (hole) transfer through DNA duplex. The results obtained may provide a guide for the molecular design of highly sensitive and selective photochemical methods for the identification and analysis of ^mC in DNA.