[Study on the interaction of tetrandrine and bovine serum albumin]

The interaction of tetrandrine with bovine serum albumin was studied by fluorescence spectra and ultra-violet spectra. The results showed that tetrandrine could quench the intrinsic fluorescence of BSA. Both static quenching and non-radiation energy transfer were the main reasons for the fluorescence quenching. The quenching constants K(sv) at different temperatures were determined using Stern-Volmer equation. The K(sv) were 1.26 x 10(4) L x mol(-1) (300 K), 1.17 x 10(4) L x mol(-1) (310 K) and 1.12 x 10(4) L x mol(-1) (320 K). According to the Forster theory of non-radiation energy transfer, the binding distances (r) were 3.24 nm (300 K), 3.31 nm (310 K) and 3.50 nm (320 K). The binding constants (KA) between tetrandrine and BSA (300 K: 1.52 x 10(5) L x mol(-1); 310 K: 2.03 x 10(5) L x mol(-1); 320 K: 2.89 x 10(5) L x mol(-1)) and thermodynamic parameters were also obtained. The thermodynamic parameters indicated that the interaction of tetrandrine and BSA was driven mainly by hydrophobic force. Results of synchronous fluorescence spectrum showed that the binding could cause conformational changes of BSA.