Oxidative Repair of Pyrimidine Cyclobutane Dimers by Nitrate Radicals (NO3 center dot): A Kinetic and Computational Study

Abstract

Pyrimidine cyclobutane dimers are hazardous DNA lesions formed upon exposure of DNA to UV light, which can be repaired through oxidative electron transfer (ET). Laser flash photolysis and computational studies were performed to explore the role of configuration and constitution at the cyclobutane ring on the oxidative repair process, using the nitrate radical (NO3•) as oxidant. The rate coefficients of 8–280 × 107 M−1 s−1 in acetonitrile revealed a very high reactivity of the cyclobutane dimers of N,N’-dimethylated uracil (DMU), thymine (DMT), and 6-methyluracil (DMU6-Me) towards NO3•, which likely proceeds via ET at N(1) as a major pathway. The overall rate of NO3• consumption was determine..