9-aminoacridine inhibits the B-Z transition of poly(dA-dT)

9-Aminoacridine is the parent compound of a family of pharmacologically active model substances that bind to DNA through intercalation between base pairs. In the present study we show that 9-aminoacridine inhibits the B-to-Z isomerization of poly(dA-dT) in conditions that otherwise cause it to occur (5 M NaCl and 123 mM Ni(ClO4)2). Higher concentrations of Ni(ClO4)2 (155 mM) are able to induce the Z-form due to the disruption of the drug-polynucleotide interaction by the metal ion. Additionally, the dye reverses the Z-form in certain conditions. Thus, the data from this study indicate that 9-aminoacridine binds preferentially to the B-form of poly(dA-dT).