Study on the interaction between amphiphilic drug and bovine serum albumin: A thermodynamic and spectroscopic description

Herein we report the interaction of amphiphilic drug clomipramine hydrochloride (CLP-a tricyclic antidepressant) with bovine serum albumin (BSA) studied by fluorescence, UV-vis, and circular dichroism (CD) spectroscopic techniques. Clomipramine hydrochloride is used to treat a variety of mental health problems. The quenching rate constant (kq) values, calculated according to the fluorescence data, decrease with increase in temperature indicating the static quenching procedure for the CLP-BSA interaction. The association binding constants (KA), evaluated at different conditions, and the thermodynamic parameters (free energy, enthalpy and entropy changes) indicate that the hydrophobic forces play a major role in the binding interaction of drug. The interaction of BSA with CLP was further confirmed by UV absorption spectra. Blue shift of position was detected due to the complex formation between the BSA-CLP. The molecular distance, r0, between donor (BSA) and acceptor (CLP) was estimated by fluorescence resonance energy transfer (FRET) whose value (4.47 nm) suggests high probability of static quenching interaction. The CD results prove the conformational changes in the BSA on binding with the drug. Thus, the results supply qualitative and quantitative understanding of the binding of BSA to CLP, which is important in understanding their effect as therapeutic agents.