Interaction of Metal Complexes of Bis(salicylidene)-ethylenediamine with DNA

Abstract

The fluorescence spectral characteristics and interaction of several metal complexes of bis(salicylidene)-ethylenediamine (salen) with DNA are described. Among the complexes tested, Co-salen bound to DNA showed a marked decrease in the fluorescence intensity with a bathochromic shift of the excitation and emission peaks. A hypochromism in the UV absorption spectra was also observed. KI quenching and competitive binding to DNA between Co-salen and ethidium bromide were studied in connection with other experimental observations to show that the interactive model between Co-salen and DNA is an intercalative one. The pH and salt effect on the fluorescence properties was also investigated. The intrinsic binding constant and the binding site number were estimated to be 5.76 × 10⁶ mol L^-1 in base pairs and 0.058, respectively. A linear relationship between F/F₀ and the concentration of calf thymus DNA covers 1.0 × 10^-6 - 5 × 10^-4 mol L^-1, which can be utilized for determining traces of calf thymus DNA with a detection limit of 4.6 × 10^-7 mol L^-1 in base pairs.