Comprehensive Study on the Binding of Iron Schiff Base Complex with DNA and Determining the Binding Mode

The iron (III) [N, N′ Bis (5-(triphenyl phosphonium methyl) salicylidene)-1, 2 ethanediamine] chloride [Fe Salen]Cl, has been synthesized and characterized as described previously. The interaction of iron complex with calf thymus (CT) DNA has been studied extensively by experimental techniques. Absorption spectra showed both hypochromism and hyperchromism. Thermal denaturation study of DNA with complex revealed the ΔTm of 5 °C. Competitive binding study shows that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by adding of the iron complex indicating that it displaces EB from its binding site in DNA and the apparent binding constant has been estimated to be 5 × 106 μM−1. Fluorescence Scatchard plot revealed type B behavior for interaction of complex to DNA. Circular dichroism (CD) spectra measurements showed that the complex interacts with DNA via surface and groove bindings. Linear dichroism (LD) measurements confirmed the bending of DNA in the presence of complex. Furthermore, Isothermal titration calorimetry (ITC) experiments approved that the binding of complex is based on both electrostatic and hydrophobic interactions. More, ITC profile exhibits the existence of two binding phases for the complex.