PMR studies of the self-association of DNA intercalating ellipticine derivatives in aqueous solution

In aqueous solution DNA intercalating ellipticine derivatives aggregate in n-mers. The self-association constants K are higher than those of 2-methoxy-6-chloro-9-[3-dimethylaminopropyl-amino]-acridine and ethidium bromide. They are of the same order as that of actinomycin D but inferior to that of acridine orange. The increase of the 9-hydroxy-ellipticine constant by addition of sodium chloride shows the importance of anion participation in the mechanism of stacking in accordance with the high energy of self-association. In the stacked n-mers the ellipticine rings are inverted. The geometry shows the importance of the orientation of the quadrupole axis in the intermolecular association of the intercalating drugs.