Adsorptive transfer stripping AC voltammetry of DNA complexes with intercalators
Using alternating current adsorptive transfer stripping voltammetry at hanging mercury drop electrode (HMDE). conformational changes of DNA due to binding of DNA intercalators were studied by means of the measurements of tensammetric DNA signals of peak 2 and peak 3. Untwisting of DNA by the intercalators in solution resulted in an altered DNA adsorption. After medium exchange and intercalator removal, the surface-confined DNA probably adopted a restrained structure, with untwisted segments attached to the electrode surface (yielding peak 2) and superhelical loops extending to the bulk of solution. This structure was more resistant to DNA surface denaturation than dsDNA adsorbed at HMDE in the absence of intercalators, which resulted in a decreased intensity of DNA peak 3. Similar effects were also observed when DNA was adsorbed at the electrode from a solution of low salt concentration. Upon introduction of DNA single-strand breaks, the specific behavior of DNA-intercalator complexes was eliminated.