Abstract: The interaction between melamine and bovine serum albumin （BSA） was investigated by using fluorescence spectroscopy, UV absorption spectroscopy and circular dichroism spectroscopy with the simulated physiological condition. The experiment results of UV absorption spectroscopy and fluorescence spectroscopy exhibited that melamine and BSA could form a kind of new compound that could be proved through the fluorescence quenching of the compound of BSA and melamine. It was the static fluorescence quenching. According to the calculation, at 28, 32 and 37 ℃, the quenching constants were 1.618×10¹², 1.614×10¹², 1.620×10¹² L/（mol·s）, respectively; The binding constants were 2.64×10³,7.59×10³ and 9.80×10³ L/mol, respectively; And the number of binding sites was 1, approximately; And the binding distance was 3.7 nm. All these indicated that a new chemical compound was produced in the mixture of BAS and melamine, and a special binding sit of BAS could only bind a one melamine molecule, and the binding distance between different sites was 3.7 nm. The results of circular dichroism displayed that melamine had a great effect on the secondary structure of BSA.

Key words: bovine serum albumin （BSA）, melamine, fluorescence spectroscopy, UV absorption spectroscopy, circular dichroism spectroscopy