A comparative spectroscopic, surface plasmon resonance, atomic force microscopy and molecular docking studies on the interaction of plant derived conferone with serum albumins

The binding mechanism of conferone, a natural sesquiterpene-coumarin, on human and bovine serum albumins (HSA/BSA), was studied using circular dichroism (CD), fluorescence and FT-IR spectroscopy as well as atomic force microscopy (AFM), surface plasmon resonance (SPR) and molecular docking methods. For real time monitoring the interaction between albumins and conferone, after immobilization of HSA/BSA on carboxymethyl dextran hydrogel Au chip (CMD) and activation of carboxylic groups on chip surface, the refractive index of metal sensor chip variations upon interaction of albumins with conferone were analyzed by SPR method, separately. The affinity values (K-A) about 1.9 x 10(6) for HSA-conferone and 1.35 x 10(6) for BSA-conferone complex demonstrated moderate affinity for conferone interaction. Further, the intrinsic fluorescences of HSA/BSA were quenched by addition of conferone through the formation of a ground state complex and static quenching mechanism. The number of binding sites (approximate to 1 for both systems), and overall binding constants (K) for HSA- conferone and BSA-conferone complexes were calculated about 10(4) and 10(2,) respectively. Analysis of the thermodynamic parameters indicated that hydrogen bonding and van der Waals interaction were major intermolecular forces between conferone and HSA/BSA. Probing the secondary structure of the albumins by FTIR, AFM and circular dichroism spectroscopy and molecular docking simulation demonstrated that, binding of conferone induces alterations in the secondary structure of albumins and suggested the subdomain IB of HSA and subdomain IA of BSA as specific binding sites for conferone interaction.