Adsorptive Stripping Analysis of DNA with Admittance Detection

Native, denatured and damaged calf thymus DNA was studied by admittance measurements using hanging mercury drop electrode. We used an adsorptive stripping technique with application of forward (negative-going) and reverse (positive-going) potential scan. The effect of alternating current voltage amplitude, frequency, adsorption potential and adsorption time was studied. Native double-stranded (ds) DNA produced peak 3 and inflexion 2 on the forward but not on the reverse curves. Irradiation of dsDNA with relatively small doses of γ-radiation (up to 80 Gy) resulted in an appearance of peak 3 and 2 on reverse voltammetric curves. Similar peaks were observed when dsDNA was sonicated. These results suggest that in damaged regions of dsDNA the bases are accessible for the interaction with the electrode producing peak 3 without passing through the potential region U around -1.2 V, where dsDNA is supposed to be slowly opened.