The allosteric effect of berberine chloride (BC), an active component of Traditional Chinese Medicine, on bovine serum albumin (BSA)-Cu2＋ binding process has been studied by 1H NMR, circular dichroism, fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy. Quantitative allosteric coefficients (βQ, βA and βn) and allosteric efficiency coefficients (γQ, γA and γn) were obtained, respectively. The negative allosteric effect of BC on the BSA intrinsic fluorescence quenching (0＜βQ＜1) and the positive allosteric effects of BC on both BSA-Cu2＋complex stability and the Cu2+-binding sites (βA＞1 and βn＞1) were observed. The degree of the allosteric effects increased with BC concentration increase. The allosteric efficiency of BC in the aspect of BSA-Cu2＋complex stability was higher than those of BSA fluorescence quenching and Cu2＋-binding sites. The BSA molecule conformational transition may be the main cause for the allosteric effect of BC.

Key words: allosteric effect, allosteric coefficient, allosteric efficiency coefficient, berberine chloride, bovine serum albumin