Study of the interaction of fangchinoline with human serum albumin by fluorescence and UV spectroscopic method

The interaction of fangchinoline with human serum albumin (HSA) was studied by use of fluorescence quenching spectra, synchronous fluorescence spectra, and ultraviolet spectra. It was shown that fangchinoline has a strong ability to quench the fluorescence of HSA. The Stern-Volmer curves based on the quenching of the fluorescence of HSA by fangchinoline indicated that the quenching mechanism of fangchinoline on HSA was static quenching and non- radiation energy transfer. Based on the Forster theory of non-radiation energy transfer, the binding distances (r) and the binding constants (K-A) between fangchinoline and HSA were found. The thermodynamic parameters obtained revealed that the interaction between fangchinoline and HSA was mainly driven by hydrophobic force. The conformational changes of HSA were investigated by use of synchronous. uorescence. The result indicates that an ionic electrostatic interaction between fangchinoline and HSA could not be excluded.