Binding of cationic dyes to DNA: distinguishing intercalation and groove binding mechanisms using simple experimental and numerical models

Simple methods for predicting intercalation or groove binding of dyes and analogous compounds with double stranded DNA are described. The methods are based on a quantitative assessment of the aspect (width to length) ratio of the dyes. The procedures were validated using a set of 38 cationic dyes of varied chemical structures binding to well oriented DNA fibers and assessing binding orientation by linear dichroism and polarized fluorescence. We demonstrated that low aspect ratio dyes bound by intercalation, whereas more rod-like dyes were groove binders. Some problems that result and possible applications are discussed briefly.