The interaction between potassium sorbate (PSA) and bovine serum albumin (BSA) was investigated by fluorescence spectroscopy

resonance lightscattering (RLS) spectroscopy. The quenching mechanism was analyzed referring to PSA against the fluorescence and the resonance light scattering spectra of BSA. The apparent binding constants (K

A

) between PSA and BSA were 223×103 L· mol

-1

 (288 K)

and 274×103 L· mol

-1

 (293 K)

respectively. The corresponding binding sites values (n) were 102 and 099. The changes of negative entropy change and enthalpy indicate that the interaction of PSA and BSA was driven mainly by electrostatic interactions. The binding process was a spontaneous process in which Gibbs free energy change was negative. The effect of PSA on the conformation of BSA was analyzed by synchronous fluorescence spectroscopy. Furthermore

the binding distance r=2.83 nm between PSA and BSA was obtained based on the mechanism of Forster non-radiation energy transfer.