Mass Spectrometry Studies on Radical Reactions of DNA

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DESCRIPTION (provided by applicant): The action of the most potent family of anticancer agents discovered thus far, the enediynes, is believed to be based on reactive ???-biradicals that abstract a hydrogen atom from each strand of double-stranded DNA. Unfortunately, the high toxicity of these agents hinders their clinical use. Various issues relating to their action, including their binding sites in DNA, the mechanism of biradical formation, its accessibility to various DNA sites, and the fate of the resulting DNA radicals, are being addressed by scientists to advance the rational design of better antitumor drugs. However, the key part of the process, the reaction of the biradical intermediate with DNA and other cellular components, remains almost entirely unexplored. Although information on the factors that control these reactions is critically needed for rational drug design, nearly nothing is known about the biradicals formed from drugs because of severe experimental difficulties in studying such highly reactive species. The goal of this research is to provide information on the role of these biradicals in cellular damage, and to advance approaches of controlling their reactivity and selectivity for drug development. A unique mass spectrometric method (developed with NIH support) for the study of biological radical reactions in the gas phase will be employed. The method involves attaching a charged group to a biradical of interest for manipulation in an FT-ICR mass spectrometer into which neutral biomolecules are introduced by laser-induced acoustic desorption. In the past, this method allowed the delineation of novel structure/reactivity relationships for reactions of mono- and biradicals with small DNA components, amino acids and small peptides. The proposed research will include 1) further studies on "tuning" of the reactivity and selectivity of biradicals, and inclusion of polyradicals, 2) examination of more complex biopolymers in order to advance a reactivity paradigm that provides predictive power for DNA and proteins, 3) development of methodology for the generation of biradicals in solution and testing of their DNA cleaving ability, and finally, 4) the mass spectrometry technology will be implemented in commercial instruments to make it accessible to other scientists, and the potential for peptide sequencing of radical reactions will be pursued. Furthermore, by improving the fundamental knowledge on oxidative DNA damage, this research advances the general understanding of aging and various diseases, including cancer.