IONIC-STRENGTH DEPENDENT BINDING MODE OF 9-AMINOACRIDINE TO DNA

The ionic strength dependent binding mode of 9-aminoacridine (9AA), a well-known DNA intercalator, to DNA is studied by flow linear dichrois m, circular dichroism, fluorescence techniques and equilibrium dialysi s. The DNA-bound 9AA exhibits spectral properties corresponding to the intercalative binding mode disregarding the salt concentrations; the angle between the long-axis transition moment of the 9AA molecule and DNA helix axis is calculated to be about 65 degrees, indicating a sign ificant deviation from the classical intercalation. At low salt concen trations, however, upwards bending curve in Stern-Volmer plot is obser ved (where 9AA is a fluorophore and DNA a quencher), indicating the co existence of both static and dynamic quenching mechanisms or the exist ence of an additional binding site.