II. Effect of Adenine on the Photodynamic Inactivation of Transforming Deoxyribonucleic Acid in the Presence of Riboflavin

Upon the addition of adenine, the marked enhancement of the riboflavin-sensitized photoinactivation of transforming deoxyribonucleic acid (DNA) of Bacillus subtHis was observed, and the inactivation of the DNA was found to be first-order reaction. The extent of the enhancement calculated from the apparent first-order rate con-stants was about seventy times. The effect of adenine was not found when methy-lene blue, thiopyronin, eosin yellowish or fluorescein was used as a sensitizer in place of riboflavin. Adenine was the most effective compound among purine and pyrimidine derivatives tested. The pH dependence of the riboflavin-sensitized photo-inactivation of the DNA in the presence of adenine was different from that observed in the absence of adenine. The rate of the riboflavin-sensitized photoinactivation increased as the temperature increased, whereas in the presence of adenine, a slight decrease in the rate was observed with increase in temperature. It was assumed from the above facts that adenine caused the enhancement of the inactivation of the DNA through the formation of a specific complex with riboflavin. It has been demonstrated that transforming can be photooxidized with riboflavin as a DNA, tobacco mosaic virus ribonucleic acid sensitizer. The finding suggested the specific (RNA) and transfer RNA can be inactivated interaction between adenine and riboflavin, by irradiation with visible light in the presence and therefore it was supposed that adenine of riboflavin (1—3). might have some influence on the photo-Adenine has been shown to be insuscep- sensitizing ability of riboflavin through the tible to the photooxidation sensitized by dyes specific interaction. such as methylene blue and lumichrome (4, In the previous reports (7, 8), it was 5). However, Uehara et al. (6~) have found shown that the riboflavin-sensitized photoin-interestingly that adenine and its nucleotides activation of yeast alcohol dehydrogenase [E