DNA Charge Transport Chemistry & Biology

项目总结/文摘

Project Summary/Abstract This proposal aims to characterize the chemistry and biology associated with DNA-mediated charge transport (CT). Specifically, roles for DNA CT in how DNA is damaged and repaired under oxidative stress will be explored. Experiments are proposed to examine oxidative DNA damage at long range as well as DNA-mediated signaling to regulatory proteins. We will examine the distance range over which oxidative damage is funneled to a control sequence in mitochondria using rhodium photooxidants to generate damage at distant sites. Mitochondrial DNA mutations and their correlations with cancers will also be determined. We will further delineate the role of DNA CT in DNA damage detection by base excision repair (BER) enzymes that contain 4Fe-4S clusters. We will prepare a series of BER enzyme mutants to characterize the path for DNA/protein CT. CT will be probed using DNA electrochemistry, EPR, transient absorption spectroscopy and AFM. In vitro protein oxidations by guanine radicals in DNA will be generated by hole injection from tethered metallointercalators. Biological assays of repair in E. coli will test how effectively mutants of two BER enzymes, MutY and Endonuclease III (EndoIII), cooperate in detecting base lesions. Correlations will be drawn between this biological helper function, DNA/protein CT studies, and cancer predispositions in human MutY homologues. DNA-mediated CT for transcriptional regulation will also be examined in soxR, a transcriptional activator from E. coli containing an Fe-S cluster. We will test the initiation of transcription from a distance through long range oxidation of DNA-bound soxR using tethered photooxidants. Paralleling these CT studies with DNA-bound proteins, we will construct DNA assemblies containing tethered metallointercalators, cyclometallated complexes of Ir and Re(CO) diimine complexes, to characterize DNA-mediated reduction chemistry versus long range DNA- mediated oxidations.