[Study on the interaction between daidzein and human serum albumin].

The binding reaction between daidzein and human serum albumin (HAS) was studied by fluorescence quenching spectra, synchronous fluorescence spectra and ultraviolet spectra. The results indicated that daidzein led to the quenching of the intrinsic fluorescence of HSA. The fluorescence quenching mechanism between daidzein and HSA was mainly static quenching, with non-radiation energy transfer occurring within single molecule. The binding constants (KA) between daidzein and HSA were 0.34 x 10(4) (23 degrees C), 1.10 X 10(4) (30 degrees C) and 4.36 x 10(4) (40 degrees C), respectively. According to the Forster theory of non- radiation energy transfer, the binding distances (r) were 1.50 nm (23 degrees C), 1.46 nm (30 degrees C) and 1.42 nm (40 degrees C), respectively. The thermodynamic parameters were calculated, which indicated that the hydrophobic force played major roles between daidzein and human serum albumin. The effect of daidzein on the conformation of HAS was investigated using synchronous spectrum.