Synthesis, DNA-binding and biological activity of a double intercalating analog of ethidium bromide

A bis-phenanthridiniun salt has been synthesized and its DNA-binding studied. Evidence provided by UV and CD spectra, by thermal denaturation profiles and by equilibrium dialysis of the drug-DNA complex lead to the conclusion that both phenanthridine moieties intercalate in the helix. The double intercalator appears to be less potent than ethidiuin chloride as an inhibitor of nucleic acid synthesis in cultured L1210 cells, though it is more potent than a monomeric analog. The low potency may be due to a low cell influx rate.