The interaction of 2-methyl-1,4-naphthoquinone (MQ) with nucleotides and DNA have been studied using KrF laser photolysis aimed at elucidation of the initial reaction mechanism. Laser spectroscopy demonstrates directly that the initial species from interaction of MQ with nucleotides are radical canons of nucleotides and MQ radical anion. Kinetic analysis indicates that formation of ion pair from interaction of any of mucleotides with MQ is synchronous with decay of triplet MQ, which has provided dynamic evidence for initiation of election transfer from DNA bases to triplet MQ, while the oxidation of TMP with slowest rate could be the rate determining step during the interaction of triplet MQ with DNA. Moreover direct observation of stabilized DNA guanyl radical canon from interaction of MQ with DNA has provided initial evidence for selective cleavage of DNA at guanine moiety, which has simulated the major, initial species produced by the action of ionizing radiation or UV light on DNA.
