Conclusions The changes in the spectral properties of compounds 13-24 on interaction with DNA and the effects of these compounds on the thermal denaturation of DNA are consistent with an intercalative mode of interaction. The 1, 4-dihydroxyanthraquinones 13-17 have a greater affinity for DNA than do the 1-hydroxy and nonhydroxylated compounds 18-24, and there is greatest activity where there are five atoms between the ring system and the basic ...