Study on the interaction of fisetholz with BSA/HSA by multi-spectroscopic, cyclic voltammetric, and molecular docking technique

Abstract

The interaction of fisetholz with bovine serum albumin (BSA) and human serum albumin (HSA) was investigated by multi-spectroscopic, cyclic voltammetric, and molecular docking technique. The results revealed that there was a static quenching of BSA/HSA induced by fisetholz. The binding constants (Ka) and binding sites (n) were calculated at different temperatures (293, 303, and 311 K). The enthalpy change (ΔH) were calculated to be –17.20 kJ mol−1 (BSA) and –18.28 kJ mol−1 (HSA) and the entropy change (ΔS) were calculated to be 35.41 J mol−1 (BSA) and 24.02 J mol−1 (HSA), respectively, which indicated that the interaction between fisetholz and BSA/HSA was mainly by electrostatic attraction. Based on displacement experiments using site probes, indomethacin and ibuprofen, the binding site of fisetholz to BSA/HSA was identified as sub-domain IIIA, which was further confirmed by molecular docking method. There was little effect of K+, Ca2+, Cu2+, Zn2+, and Fe3+ on fisetholz-BSA or fisetholz-HSA complex. The spectra of synchronous fluorescence, circular dichroism (CD) and Fourier transform infrared (FT-IR) all showed that fisetholz binding to BSA/HSA leads to secondary structures change of the two serum albumins. According to the Förster non-radiation energy transfer theory, the binding distance between fisetholz and BSA/HSA was 2.94/4.68 nm. The cyclic voltammetry as a supporting tool also indicated that fisetholz interacted with protein.Communicated by Ramaswamy H. Sarma