Product analysis and mechanistic studies of radical-mediated DNA damage

我的研究项目致力于了解DNA损伤的化学过程。DNA是由一串连续的交替DNA碱基组成的，这些碱基定义了通过重复的糖和磷酸盐亚结构连接在一起的遗传密码（T，A，G，C）。X射线和其他类型的电离辐射破坏化学键，导致产生自由基物质。许多物理和化学试剂也会产生自由基物质，如过氧化氢和其他天然氧化剂，它们是由需氧生物体中的生化反应产生的。反过来，这些自由基物质可以与DNA亚结构（DNA碱基，糖和磷酸基团）反应，以诱导DNA一级结构的变化。化学变化的集合，统称为DNA损伤，可以产生严重的短期影响，如细胞死亡和长期后果，如基因突变。我们对涉及在小分子尺度上形成DNA损伤的途径有相当好的理解，所述小分子尺度是特定自由基物质和简单分子靶点的混合物（即，小片段DNA而不是整个DNA分子）。然而，由于DNA碱基的序列和3D聚合物结构，从初始自由基物质到最终损伤的途径在DNA中要复杂得多。事实上，与DNA物理结合的自由基与溶液中的自由基相比具有不同的反应性，因为它们移动和与反应伙伴碰撞的能力有限。我的研究计划侧重于DNA自由基介导的化学的特定领域，这些领域仍然令人困惑或知之甚少，但对物理学和生物学界面的未来进步至关重要。我将集中在低能电子与DNA的反应，DNA内的氮为中心的自由基的反应性，重要的过氧自由基中间体的反应性，以及涉及两个或两个以上的损伤部位的簇状病变的形成。这些研究将使用一系列精密仪器，包括独特的辐射源和方法，包括液相色谱法、质谱法、核磁共振分析。

My research program strives to understand the chemistry of DNA damage. DNA is composed of a continuous string of alternating DNA bases that define the genetic code (T,A,G,C) connected together by repeating sugar and phosphate sub-structures. X-rays and other types of ionizing radiation break chemical bonds resulting in the generation of radical species. Numerous physical and chemical agents also create radical species, such as hydrogen peroxide and other natural oxidants that are generated by biochemical reactions in aerobic organisms. In turn, these radical species can react with DNA sub-structures (DNA bases, sugar and phosphate groups) to induce changes in the primary structure of DNA. The ensemble of chemical changes, referred collectively as DNA damage, can have serious short-term effects such as cell death and long-term consequences, such as genetic mutations. We have a fairly good understanding of the pathways that are implicated in the formation of DNA damage on a small molecule scale that is with mixtures of specific radical species and simple molecular targets (i.e., small pieces of DNA instead of the entire DNA molecule). However, the pathway going from initial radical species to ultimate damage is much more complicated in DNA due to the sequence of DNA bases and the 3D polymer structure. Indeed, radicals that are physically bound to DNA have a different reactivity compared to free radicals in solution because of limitations in their ability to move around and collide with reaction partners. My research program focuses on specific areas of DNA radical-mediated chemistry that are still confusing or poorly understood yet crucial to future advancements at the interface of physics and biology. I will focus on the reaction of low energy electrons with DNA, the reactivity of nitrogen-centered radicals within DNA, the reactivity of important peroxyl radical intermediates, and the formation of clustered lesions involving two or more sites of damage in close proximity. These studies will be achieved with an arsenal of sophisticated instrument, including unique radiation sources, and methods, including liquid chromatography, mass spectrometry, nuclear magnetic resonance analysis.