Characterization by 32P-postlabelling of 8-methoxypsoralen adducts

8-Methoxypsoralen is a bifunctional furocoumarin used in human photochemotherapy. It can form two kinds of DNA adduct, monoadducts and interstrand cross-links. These adducts have been detected by 32P-postlabelling using hydrolysis with DNase1, alkaline phosphatase and snake venom phosphodiesterase, and longer labelling than usual, with more T4 polynucleotide kinase. Using preliminary two-dimensional chromatography (D1, D2) followed by transfer of adducts to separate PEI cellulose sheets for further development (D3, D4), we observed three spots corresponding to the adducts sought. Two experiments (dose-effects and shift of radioactivity) have confirmed the origin of the three spots.