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是由一串连续交替的DNA碱基组成的，这些碱基定义了遗传密码（T, a，G，C），通过重复的糖和磷酸盐亚结构连接在一起。x射线和其他类型的电离辐射会破坏化学键，从而产生自由基。许多物理和化学试剂也会产生自由基，如过氧化氢和其他由有氧生物的生化反应产生的天然氧化剂。反过来，这些自由基可以与DNA亚结构（DNA碱基、糖和磷酸基）反应，诱导DNA初级结构的变化。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。我们对在小分子尺度上形成DNA损伤的途径有了相当好的理解，这种小分子尺度是由特定的自由基和简单的分子靶标（即DNA的小片段而不是整个DNA分子）混合而成的。然而，由于DNA的碱基序列和三维聚合物结构，从初始自由基到最终损伤的途径要复杂得多。事实上，与溶液中的自由基相比，与DNA物理结合的自由基具有不同的反应活性，因为它们移动和与反应伙伴碰撞的能力受到限制。我的研究项目集中在DNA自由基介导化学的特定领域，这些领域仍然令人困惑或知之甚少，但对物理学和生物学的未来发展至关重要。我将重点关注低能电子与DNA的反应，DNA内氮中心自由基的反应性，重要的过氧自由基中间体的反应性，以及涉及两个或多个近距离损伤部位的聚集性损伤的形成。这些研究将通过一系列复杂的仪器，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.