Investigation of the interaction between sophoricoside and human serum albumin by optical spectroscopy and molecular modeling methods

摘要

The interaction of sophoricoside and human serum albumin (HSA) was investigated by UV-absorption, fluorescence spectroscopy and Fourier transform infrared (FT-IR) spectroscopy at simulative physiological pH with sophoricoside concentrations of 3.0 X 10(-6) to 2.3 x 10(-5) mol L-1. The experimental results suggested that the intrinsic fluorescence of HSA was quenched by addition of sophoricoside through static quenching mechanism. The interaction between sophoricoside and HSA was occurred via a single class of binding site. The binding constants at 290, 301, 310 and 318 K were 6.19 x 10(4), 4.69 x 10(4), 3.54 x 10(4), 3.11 x 10(4) L mol(-1), respectively. In the presence of sophoricoside the protein secondary structure changed in aqueous solution. The standard enthalpy change (-19.44 kJ mol(-1)) and standard entropy change (24.71 J mol(-1) K-1) of the binding reaction revealed that hydrophobic interaction was the predominant binding force. In addition, molecular modeling showed that sophoricoside was bound within the subdomain IIA of the HSA.