三种香豆素类中药小分子与牛血清白蛋白的相互作用

运用荧光光谱(FS)、紫外光谱(UV)法研究了三种香豆素中药小分子与牛血清白蛋白(BSA)的相互作用．实验结果表明，香豆素类小分子能够插入BSA分子内部与BSA形成基态复合物导致BSA内源荧光猝灭，猝灭机理主要为静态猝灭和非辐射能量转移．药物分子极性及体积增大对BSA内源性荧光猝灭效应增强，与BSA中荧光性氨基酸残基之间的空间距离r增大，表观结合常数KA增大且结合位点数n减少．结合过程的热力学参数变化表明上述相互作用过程是一个熵增加、Gibbs自由能降低的自发分子间作用过程，其中香豆素与BSA之间以疏水作用为主，而伞形花内酯、七叶内酯与BSA之间则还存在偶极-偶极作用，表明药物分子极性同样影响其与BSA间相互作用力的类型．

Interaction between Natural Pharmaceutical Homologues of Coumarin and Bovine Serum Albumin

The interaction between bovine serum albumin (BSA) and such a natural pharmaceutical homologue as coumarin, umbelliferone and aesculetin was investigated using fluorescence spectroscopy (FS) and ultraviolet spectroscopy (UV). The experimental results showed that the homologues inserted into the hydrophobic pockets of BSA, quenching the inner fluorescence of BSA by forming the pharmaceutical-BSA complex. Both static quenching and nonradiative energy transferring were confirmed to result in the fluorescence quenching. It was found that the enlargement of molecular polarity and volume of the pharmaceutics caused the increment of the quenching efficiency, the stereo-distance (r) and the apparent binding constant (K A) between pharmaceutical molecule and BSA, and the decrement of binding sites (n) of pharmaceutical molecule on BSA. The process of binding homologue molecule on BSA was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. The interaction between the coumarin and BSA was driven mainly by hydrophobic force whereas both hydrophobic force and dipole-dipole force coexisted in umbelliferone-BSA and aesculetin-BSA systems, which indicated that the driving forces of the pharmaceutical-BSA interaction changed with the molecular polarity of pharmaceuticals, too.