Probing the Binding of Bicyclol and Human Serum Albumin by Multispectral Technologies and Molecular Docking Method

In this paper, under the condition of a simulated human physiological environment, steady-state fluorescence, UV spectra, three-dimensional fluorescence, time-resolved fluorescence, and the circular dichroism were implemented to investigate the binding mechanism between bicyclol (BYL) and human serum albumin (HSA). The results revealed a red shift in the UV absorption wavelength of HSA and an increase in absorption intensity of HSA with increasing concentration of bicyclol. Bicyclol quenched the intrinsic fluorescence of HSA via a static quenching mechanism. At 298 K, the number of binding sites (n) and binding constant of BYL-HSA were about 1 and 9.67 x 10(3) L center dot mol(-1), respectively. The thermodynamic parameters Delta G, Delta H, Delta S are - 22.76 and - 19.07 kJ center dot mol(-1) and 27.17 J center dot K-1 center dot mol(-1) respectively, which demonstrated that the binding of bicyclol and HSA was mainly driven by hydrophobic and electrostatic forces. In addition, the molecular docking method was utilized to further investigate the binding site when BYL is combined with HSA, which indicated that BYL is bound on the hydrophobic cavities of sub-domains IIA and IIIA of HSA, respectively, and that the binding affinity in the IIIA site was much higher than that in the IIA site.