A comparative study on the binding of single and double chain surfactant–cobalt(III) complexes with bovine serum albumin

Abstract

The comparative binding effect of single and double aliphatic chain containing surfactant–cobalt(III) complexes cis-[Co(bpy)2(DA)2](ClO4)3⋅2H2O (1), cis-[Co(bpy)2(DA)Cl](ClO4)2⋅2H2O (2), cis-[Co(phen)2(CA)2](ClO4)3⋅2H2O (3), and cis-[Co(phen)2(CA)Cl](ClO4)2⋅2H2O (4) with bovine serum albumin (BSA) under physiological condition was analyzed by steady state, time resolved fluorescence, synchronous, three-dimensional fluorescence, UV–Visible absorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of BSA through a static mechanism. The binding constants (Kb) and the number of binding sites were calculated and binding constant values are found in the range of 104–105M−1. The results indicate that compared to single chain complex, double chain surfactant–cobalt(III) complex interacts strongly with BSA. Also the sign of thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicate that all the complexes interact with BSA through hydrophobic force. The binding distance (r) between complexes and BSA was calculated using Förster non-radiation energy transfer theory and found to be less than 7nm. The results of synchronous, three dimensional fluorescence and circular dichroism spectroscopic methods indicate that the double chain surfactant–cobalt(III) complexes changed the conformation of the protein considerably than the respective single chain surfactant–cobalt(III) complexes. Antimicrobial studies of the complexes showed good activities against pathogenic microorganisms.