金属离子对次野鸢尾黄素与牛血清白蛋白相互作用的影响

Effect of Metal Ions on the Interaction Between Bovine Serum Albumin and Irisflorentin

应用荧光光度法研究了金属离子Fe^3＋、Ca^2＋、Cu^2＋或Mn^2＋对次野鸢尾黄素（IFR）与牛血清白蛋白（BSA）相互作用的影响。实验结果表明，不存在金属离子时，IFR对BSA的荧光猝灭过程为动态猝灭，其结合过程的表观结合常数KA值为10^4～10^5数量级，结合位点数；r／约等于1。由热力学参数得出IFR与BSA结合过程是一个熵增加、Gibbs自由能降低的自发过程，分子间相互作用力以疏水作用力为主。在Fe^3＋或Ca^2＋的存在下，IFR对BSA的荧光猝灭类型由动态猝灭转变为静态猝灭，作用力类型也由以疏水作用力为主转变为以氢键与范德华力为主或以静电引力为主。Cu^2＋或Mn^2＋存在下，IFR对BSA的荧光猝灭类型及分子间作用力类型均没有发生改变。四种金属离子的参与都使得IFR与BSA结合作用的表观结合常数发生了明显的变化，但结合位点数仍维持在1左右。

The effect of metal ions on the interaction between bovine serum albumin （BSA） and irisflorentin （IFR） was investigated with the use of fluorescence spectroscopy. Results obtained from analysis of fluorescence spectra indicated that IFR had a strong ability to quench the intrinsic fluorescence of BSA through a dynamic quenching procedure in the absence of metal ions. The apparent association constant KA in IFR-BSA binding process was about 10^4-10^5 and the number of binding sites of IFR on BSA was about 1. Binding of IFR to BSA was a spontaneous supramolecular interaction in which entropy increased and Gibbs free energy decreased. The major driving force in IFR-BSA binding process was hydrophobic force. But in the presence of Fe^3＋ or Ca^2＋, the type of BSA intrinsic fluorescence quenching by IFR were changed from dynamic quenching to static quenching, and the main driving force in IFR-BSA binding process was also changed from hydrophobic force to hydrogen bond formation and van der Waals forces or electrostatic forces. Whereas, in the presence of Cu^2＋ or Mn^2＋ , neither the type of BSA intrinsic fluorescence quenching nor the main driving force in IFR-BSA binding process were changed. The value of the apparent association constant KA in IFR-BSA binding process was changed evidently in the presence of one of the four metal ions at different temperatures, but the number of binding sites of IFR on BSA was still about 1.