Fluorescence study on the interaction of human serum albumin with loureirin B

The interaction between loureirin B (Lour B) and human serum albumin (HSA) was investigated by fluorescence and UV-vis absorption spectroscopy. Experimental results indicated that loureirin B had a strong ability to quench the intrinsic fluorescence of HSA through a dynamic quenching procedure. The fluorescence quenching data revealed that the quenching constants (KSV) 2.68 x 10(4), 3.30 x 10(4) and 4.10 x 10(4) l/mol at 300, 310 and 320 K, respectively. Based on the thermodynamic parameters obtained, the positive values of enthalpy change Delta H and entropy change Delta S suggested that hydrophobic forces played a major role in the interaction of Lour B with HSA. According to Forster theory of energy transfer, the distance r between HSA and Lour B was calculated to be 2.85 nm. Furthermore, the effect of Lour B on the conformation of HSA was analyzed by synchronous fluorescence and three-dimensional fluorescence spectra.