Product analysis and mechanistic studies of radical-mediated DNA damage

我的研究项目致力于了解DNA损伤的化学原理。DNA由一串交替的DNA碱基组成，这些碱基通过重复的糖和磷酸亚结构连接在一起，定义了遗传密码(T、A、G、C)。X射线和其他类型的电离辐射会破坏化学键，导致自由基物种的产生。许多物理和化学制剂也会产生自由基物种，如过氧化氢和其他天然氧化剂，它们是由好氧生物体中的生化反应产生的。反过来，这些自由基物种可以与DNA亚结构(DNA碱基、糖和磷酸基团)反应，导致DNA一级结构的变化。一连串的化学变化统称为DNA损伤，可能会产生严重的短期影响，如细胞死亡和长期后果，如基因突变。我们对小分子尺度上DNA损伤的形成途径有相当好的理解，即特定自由基物种和简单分子靶标的混合物(即，小片段DNA而不是整个DNA分子)。然而，由于DNA碱基序列和三维聚合物结构的影响，DNA中从初始自由基物种到最终损伤的途径要复杂得多。事实上，物理上与DNA结合的自由基与溶液中的自由基相比，具有不同的反应活性，因为它们在移动和与反应伙伴碰撞的能力方面存在局限性。我的研究项目专注于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，但对未来物理学和生物学的发展至关重要。我将集中讨论低能电子与DNA的反应，DNA中以氮为中心的自由基的反应性，重要的过氧基中间体的反应性，以及涉及两个或更多邻近损伤部位的簇状损伤的形成。这些研究将利用包括独特的放射源在内的各种尖端仪器和方法，包括液相色谱、质谱分析、核磁共振分析等手段来实现。

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.