PHOTOREACTION OF FUROCOUMARINS WITH DNA IS SIMILARLY INHIBITED BY MINOR AND MAJOR GROOVE-INTERACTING LIGANDS

It was found that methyl green, a major groove binding ligand and the minor groove binding ligands, netropsin and 2,7-di-tert-butylproflavin e inhibit, to a similar extend a monoadduct forming benzopsoralen and monoadduct and diadduct forming derivatives of psoralen (8-methoxypsor alen and 3,4'-dimethyl-8-methoxypsoralen). Caffeine exhibits an inhibi tory effect on furocoumarin photobinding to DNA at 10(3) fold higher c oncentration. Together with the previously published results it is con cluded that both occupancy of the major and minor groove as well as in tercalation hinder photobinding of furocoumarins to DNA.