Generation and photosensitization properties of the oxidized radical of riboflavin: a laser flash photolysis study

Using 248 nm laser flash photolysis, it has been demonstrated that the neutral oxidized radical of riboflavin (RF(-H)(.)) resulting from rapid deprotonation of the radical cation (RF.+) can be generated via monophotonic ionization when it is directly excited with a 248 nm laser and via oxidation by the SO4.- radical in aqueous solution. The RF(-H)(.) or RF.+ reacts with both purine nucleotides and pyrimidine nucleotides via electron transfer to give the radical cations of nucleotides. These results suggest that the reactions of oxidized riboflavin radical might be involved in DNA photosensitization in vivo and in vitro. (C) 1999 Elsevier Science S.A. All rights reserved.