Study of DNA-deltamethrin binding by voltammetry, competitive fluorescence, thermal denaturation, circular dichroism, and atomic force microscopy techniques

The interaction of deltamethrin (DM), a synthetic insecticide, with calf thymus DNA was studied. The cyclic voltammetric (CV) results revealed that DM has two irreversible cathodic peaks. The first peak (a) was devoted to reduction of -CN by 4 electrons and the second peak (b) was devoted to reduction of the -C = C- moiety by two electrons. By using non-linear regression analysis of CV data of peak (a), the binding constant, binding site size, and diffusion coefficient for free DM (D(f)) and DNA-DM (D(b)) were calculated as: 2.6 × 10(4), 1.6, 3.2 × 10(-4)Cm(2) S(-1), and 8.5 × 10(-6)Cm(2) S(-1), respectively. The thermal denaturation, competitive fluorescence, and AFM results revealed that the mode of interaction may be non-intercalative. Also the circular dichroism spectra showed that the conformation of CT DNA was converted from right-handed B-DNA to A-DNA due to the destacking of the adjacent guanine bases in pH 7.3 solution.