Biophysical studies of single and double alkyl chain metallosurfactants in presence of ionic liquids as additive on its binding to calf thymus DNA

Abstract

In this work, a binding study of DNA in ionic liquid media of single and double alkyl chain metallosurfactants types (trans-[Co(DH)2(HA)Cl]2+ (1) and trans-[Co(DH)2(HA)2]3+ (2)) where DH = dimethyl glyoxime and HA = hexadecylamine, have been carried out by various spectral techniques. The experimental results indicating that size and shape of the ligand and hydrophobicity of these complexes marked effect on the binding affinity of the complexes to CT DNA in groove binding mode and the order of their intrinsic DNA binding constants kb is kb = 1.2 × 105 (1) < kb 3.6 × 105 (2). In the presence of an ionic liquid additive, the binding strength of the surfactant-cobalt(III) complex to the DNA increased due to the double alkyl chain of metallosurfactant, being more hydrophobic, exhibits strong binding towards DNA in comparison to the single alkyl chain. This indicates that the long aliphatic chain amine ligand/s present in the metallosurfactant-oxime complex (2) play a definite role in the binding between the metallosurfactant-oxime complex and DNA through their hydrophobicity. Ethidium bromide (EB) shows that these complexes exhibit the ability to displace the DNA-bound EB indicating that the complexes bind to DNA in groove binding site. Observed changes in the circular dichoric spectra of DNA in the presence of metallosurfactant complexes support the strong binding of complexes with DNA. Cyclic voltammetry results also confirm this mode of binding. The results reveal that the extent of DNA binding of (2) was greater than that of (1).