Product analysis and mechanistic studies of radical-mediated DNA damage

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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.