Interaction of isofraxidin with human serum albumin.

This study was designed to examine the interaction of isofraxidin with human serum albumin (HSA) under physiological conditions with drug concentrations in the range of 3.3 x 10(-6) mol L(-1)-3.0x10(-5) mol L(-1) and HSA concentration at 1.5 x 10(-6) mol L(-1). Fluorescence quenching methods in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy were used to determine the drug-binding mode, the binding constant and the protein structure changes in the presence of isofraxidin in aqueous solution. Spectroscopic evidence showed that the interaction results in one type of isofraxidin-HSA complex with binding constants of 4.1266 x 10(5) L mol(-1), 3.8612 x 10(5) L mol(-1), 3.5063 x 10(5) L mol(-1), 3.1241 x 10(5) L mol(-1) at 296 K, 303 K, 310 K, 318 K, respectively. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS) were calculated to be -10.08 kJ mol(-1) and 73.57 J mol(-1) K(-1) according to van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to HSA. The experiment results are nearly in accordance with the calculation results obtained by Silicon Graphics Ocatane2 workstation.