Interaction of antitumour agent mitoxantrone with poly[d(G-C)]--a circular dichroic study.

The binding of antitumour drug mitoxantrone [1,4-dihydroxy-5, 8-bis [2-(2-hydroxy ethyl)amino)ethyl)amino)-9, 10-anthracenedione] to the synthetic polynucleotide poly[d(G-C)] was studied by circular dichroic titrations. The interaction induced intense chiroptical properties in the visible (688 nm) as well as the ultraviolet (260, 320 nm) region in an otherwise optically inactive drug. The interaction occurs in two stages, one below a drug/nucleotide ratio of 0.11 and other above this value. The second mode of interaction causes an almost cooperative enhancement of the visible induced circular dichroism (ICD).