Investigation of Reactions of Radiation-Produced Electrons with Azido-Nucleosides: Formation and Identification of Radical Intermediates

This project elucidates the mechanisms involved in the formation of site-specific pi-type neutral aminyl radicals (pi-RNH•) via the reaction of radiation-produced electrons with certain azido-DNA model systems including azidonucleosides in the absence of oxygen. Subsequent reactions of these oxidizing pi-RNH• that were produced reductively, were investigated. Experimental investigations on formation of these pi-RNH• and their subsequent reactions were carried out using Electron Spin Resonance (ESR) spectroscopy. The hyperfine coupling constant (HFCC) values were calculated employing Density Functional Theory (DFT). Combination of ESR spectral studies and DFT calculations led to radical assignments and interpretations of ESR spectra. Reactions of these pi-RNH• would reveal whether these azido-DNA model systems can be applied as potential radiosensitizers (compounds which augment radiation damage), used for radio-chemotherapy of tumors.