Exploring the Interaction of Ethidium Bromide and HOECHST 33258 with DNA by Means of Electrochemical Approach

Abstract

The binding of both ethidium bromide (EtBr) and Hoechst 33258 (H33258) to calf thymus DNA differing by the mechanism at different ionic strengths of NaCl water solutions (2, 20 and 150mM) has been quantitatively studied by square wave voltammetry (SWV). It was revealed that EtBr binds to DNA by more than one mode: at the solution ionic strengths 2 and 150mM, two modes were revealed, at 20mM — three modes. Values of EtBr binding constant (K) to DNA and the number of nucleotides per one binding site (n) for respective binding modes were determined. For H33258 under the same conditions, two binding modes were found and for both these modes values of K and n were determined. Dependence of the binding types and parameters on the solution ionic strength by SWV method was revealed, which differs by the binding type of EtBr and H33258. The obtained data are in good accordance with the ones determined by spectroscopic (absorption and fluorescence) and differential pulse voltammetry (DPV) methods. The obtained data indicate the sensibility and high precision of SWV method which may be applied to studies on interaction of different ligands with DNA, which reveal some peculiarities of their binding to DNA that are hidden and are not found by other methods.