Mechanistic studies of radical-induced DNA damage

电离辐射、光敏、氧和氮自由基以及某些化学物质对DNA损伤的形成涉及以DNA成分为中心的有机自由基的产生。这些自由基产生不稳定和稳定的抗磁性产物，通常被称为DNA损伤。我们对DNA损伤的大部分知识都是基于单体暴露于自由基生成系统（如电离辐射）的研究。然而，今天很清楚的是，DNA序列和二级结构极大地影响了初级损伤物种的反应和随后的有机自由基的命运。我的长期研究目标是DNA损伤的表征和导致损伤形成的机制的阐明。在接下来的5年里，我的研究计划的目标是推进我们对DNA暴露于电离辐射（即x射线，伽马射线，带电粒子）和其他氧化剂和还原剂产生的两个重要自由基家族的化学基础知识。一个家族包括含有外环氨基的DNA碱基氮中心自由基（腺嘌呤、胞嘧啶、5-甲基胞嘧啶）。这些自由基产生于DNA的直接电离或高活性羟基自由基的反应。另一类自由基是由分子直接电离过程中产生的低能电子（0- 30ev）反应产生的。为了实现我的具体目标，我将(a)合成新的DNA碱基光活性衍生物，(b)使用色谱和质谱法表征含有这些衍生物的辐照DNA的全谱修饰，并研究DNA结构对产物形成的影响。这些研究将极大地增加我们对自由基诱导的DNA损伤的最基本的认识，促进我们研究DNA修复和诱变的能力，并有助于发现DNA损伤的生物标志物，这将使我们能够评估有毒物质和药物的遗传后果。

The formation of DNA damage by ionizing radiation, photosensitization, oxygen and nitrogen free radicals, and certain chemicals involves the generation of organic radicals centered on DNA components. These radicals give rise to unstable and stable diamagnetic products, commonly referred to as DNA damage. Much of our knowledge about DNA damage is based on studies in which monomers are exposed to radical generating systems such as ionizing radiation. However, it is clear today that the reaction of primary damaging species and the fate of subsequent organic radicals are greatly affected by DNA sequence and secondary structure. My long term research program targets the characterization of DNA damage and the elucidation of mechanisms leading to the formation of damage. The goal of my research program over the next 5 years is to advance our basic knowledge on the chemistry of two important families of radicals generated by the exposure of DNA to ionizing radiation (i.e., x-rays, gamma-rays, charged particles), and other oxidizing and reducing agents. One family includes nitrogen centered radicals of DNA bases containing an exocyclic amino group (adenine, cytosine, 5-methylcytosine). These radicals arise from either the direct ionization of DNA or the reaction of highly reactive hydroxyl radicals. The other family includes radicals generated by the reaction of low energy electrons (0-30 eV) that are ejected during the direct ionization of molecules. To accomplish my specific goals I will (a) synthesise novel photoactive derivatives of DNA bases, (b) characterize the full spectrum of modifications in irradiated DNA containing these derivatives, using chromatography and mass spectrometry, and investigate the effects of DNA structure on the formation of products. These studies will greatly increase our most fundamental knowledge of radical-induced DNA damage, facilitate our ability to study DNA repair and mutagenesis, as well as contribute to the discovery of biomarkers of DNA damage that will allow us to assess the genetic consequences of toxic agents and drugs.