Effect of adiphenine hydrochloride on the structure of bovine serum albumin: Spectroscopic and docking study

The interaction of adiphenine hydrochloride (ADP) with bovine serum albumin (BSA) has been investigated by fluorescence, time resolved fluorescence, UV- visible, FTIR and tensiometric technique. Molecular docking has also been done to show the available binding sites on BSA for ADP. Critical micelle concentration (cmc), surface excess (T-max), the minimum area per molecule (A(min)), and molar free energy at the maximum adsorption attained at cmc (G(min)) were evaluated to study the interfacial properties of ADP. Fluorescence spectroscopy was used to observe the effective quenching mechanism between BSA and ADP which was further confirmed by time-resolved fluorescence spectroscopy. Different thermo-dynamic parameters such as molar enthalpy (Delta H), molar Gibbs free energy (Delta G), and molar entropy contribution (Delta S) were evaluated by using van't Hoff equation which showed that the binding mechanism was enthalpy driven and the major forces involved between ADP and BSA interaction are van der Waals and hydrogen bonding. UV-vis spectroscopy results showed the complex formation between ADP and BSA. Synchronous fluorescence spectra reveal that there is a slight effect of ADP on the fluorescence intensity of tyrosine but a significant effect on tryptophan residue of BSA. FTIR results suggested the ADP induced conformational changes in BSA. In addition, the molecular docking and competitive binding results showed that the ADP molecule binds with BSA on Sudlow site I (subdomain IIA). The esterase-like enzymatic activity study revealed that the ADP inhibits the enzymatic activity of BSA. (C) 2019 Elsevier B.V. All rights reserved.