The topic of the present study is the establishment of sensitive and accurate methods for the detection of structural moifications of DNA caused by covalent and non-covalent interaction with nucleophilic drugs. Two dimensional gel electrophoresis of DNA, under different experimental conditions provided an accurate measurement of the superhelical densities, the directions of the superhelical turns, the binding constants, and the relative enthalpies and entropies of DNA bound by intercalating drugs. The forms of interactions were studied by a number of techniques, such as electron microscopy, NMR, spectroscopic analysis. Data obtained were analyzed by computer graphic technology to observe possible atomic configurations.