Binding of isofraxidin to bovine serum albumin

The binding of isofraxidin to bovine serum albumin (BSA) was studied under physiological conditions with BSA concentration of 1.5 x 10(-6) mol (.) L-1 and drug concentration in the range of 1.67 x 10(-6) mol (.) L-1 to 2.0 x 10(-5) mol (.) L-1. Fluorescence quenching spectra in combination with uv absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and CD spectroscopy was used to determine the drug-binding mode, binding constant, and the protein structure changes in the presence of isofraxidin in aqueous solution. The linearity of Scatchard plot indicates that isofraxidin binds to a single class of binding sites on BSA and the values given for the binding constants agree very closely with those obtained by the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (AS), were calculated to be - 17.63 kJ (.) mol(-1) and 51.38 J (.) mol(-1) (.) K-1 according to the van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to BSA. (C) 2004 Wiley Periodicals, Inc.