Study on the binding of farrerol to human serum albumin

Binding of farrerol to human serum albumin (HSA) was investigated at 293, 303, and 313 K and pH 7.40 using spectrophotometric technique and molecular modeling. The binding parameters obtained from the modified Scatchard's procedure were in close agreement with those from Stern–Volmer equation. Based on the thermodynamic parameters calculated from the van’t Hoff equation, the enthalpy change ΔH° and entropy change ΔS° for the process of farrerol binding to HSA were evaluated at −18.51 kJ mol−1 and 47.52 J mol−1 K−1, respectively. The value of 2.63 nm for the distance r between the donor (HSA) and acceptor (farrerol) was derived from the fluorescence resonance energy transfer. From these results, three issues on the interactions between farrerol and HSA could be approached: (a) farrerol is strongly bound to HSA, (b) the primary binding site is located at the site I of HSA, and (c) apart from hydrophobic interactions, there still exist hydrogen bond interactions between farrerol and the residues of HSA, such as Lys195, Arg218, Arg222, and Ala291. Besides, the conformational change of HSA was observed, being caused by the interaction with farrerol.