牛血清白蛋白-Cu^(2+)结合过程中盐酸小檗碱的变构效应

Allosteric Effect of Berberine Chloride on Bovine Serum Albumin-Cu^(2+) Binding Process

用核磁共振(1HNMR)、圆二色谱(CD)、荧光光谱(FS)以及紫外光谱(UV)技术考察了中药有效成分盐酸小檗碱(BC)对牛血清白蛋白(BSA)-Cu2+结合过程的变构效应,得到分别表征BSA内源荧光猝灭、BSA-Cu2+复合物稳定性以及Cu2+在BSA分子上的结合位点发生变构的定量效应参数βQ(βA和βn)和效率参数γQ(γA和γn).结果表明,BC对Cu2+猝灭BSA内源荧光呈负变构效应(0<βQ<1),而对BSA-Cu2+复合物稳定性以及Cu2+在BSA分子上的结合位点呈正变构效应(βA>1,βn>1);变构效应随BC浓度增加而增强,BC对BSA-Cu2+复合物稳定性的变构效率明显高于其对荧光猝灭和结合位点的变构;BSA分子构象转变是变构效应的主要原因.

The allosteric effect of berberine chloride （BC）, an active component of Traditional Chinese Medicine, on bovine serum albumin （BSA）-Cu^2＋ 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-Cu^2＋complex stability and the Cu^2＋ -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-Cu^2＋complex stability was higher than those of BSA fluorescence quenching and Cu^2＋-binding sites. The BSA molecule conformational transition may be the main cause for the allosteric effect of BC.