Dependence of the mutagenic power of heteroatomic dyes on their DNA-base-pair specificity.

23 compounds structurally related to proflavine were tested with Salmonella typhimurium TA1537 for their ability to induce mutants in the quantitative mutagenicity test of Ames et al. Of these compounds, 13 were mutagenic. Their mutagenic power decreased with increasing GC specificity of the dye. Because the mutational site in the tester strain is assumed to consist of a run of 4 adjacent GC pairs of the same polarity we conclude that for mutation to occur the dye should not be bound within this run of identical base pairs. Some of the compounds showed a negative slope at higher concentrations. Because these dyes also showed a comparatively high tendency to dimerize we conclude that mutation induction requires the intercalator to be bound as a monomer. Those compounds that were not mutagenic either did not intercalate or were inactivated by reduction.