Determination of binding geometry of DNA-adduct systems through induced circular dichroism

Many molecules (adducts) bound to DNA are postulated to intercalate between successive DNA base pairs. Linear dichroism (LD) has been used to yield information about the angular orientation of the adduct relative to the helix axis, but cannot probe the orientation within the plane perpendicular to this axis. A model is presented in this paper which predicts that the degree of alignment relative to a DNA fixed axis in this plane may be directly probed through the sign of the circular dichroism (CD) induced in an adduct transition of known polarization. Comparison with experimental data suggests that the method can complement LD studies in giving detailed information about the binding geometry.