In-vitro binding analysis of bovine serum albumin with sulindac/chlorpromazine: Spectroscopic, calorimetric and computational approaches

The current study was undertaken to explore the bindingof sulindac (SDC), and chlorpromazine (CPZ) with the bovine serum albumin (BSA) by fluorescence, isothermal titration calorimetric (ITC), UV-visible, site marker, circular dichroism (CD), and molecular docking studies. The fluorescence intensity of native BSA was quenched on increasing concentration of SDC/CPZ in a static manner. The thermodynamic parameters, association constant (K-a), standard enthalpy change (Delta H degrees), standard entropy change (Delta S degrees) and standard Gibbs free energy change (Delta G degrees) were obtained from ITC. Site marker experiment highlighted that SDC/CPZ binds at Sudlow's site I by using warfarin and ibuprofen probes for site I and site II, respectively. The distance between donor, BSA and acceptor, SDC/CPZ was calculated by applying the FRET theory. Alteration in the secondary structure of BSA by SDC/CPZ was revealed by UV-vis, synchronous and 3D fluorescence studies. The stability of native BSA increases and decreases, respectively in the presence of SDC and CPZ as shown by CD spectroscopy. Molecular docking was performed to further confirm the binding site, amino acid residues and type of interactions involved in the binding process. This study provides an insight into interaction at molecular level between SDC/CPZ and BSA and will help to understand the thermodynamics and mechanism of drug binding. (C) 2019 Elsevier B.V. All rights reserved.