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.