胡椒酸乙酯与牛血清白蛋白的相互作用及金属离子的影响

采用荧光光谱研究了胡椒酸乙酯与牛血清白蛋白(BSA)的相互作用。实验结果表明:胡椒酸乙酯与BSA形成基态复合物从而猝灭BSA的内源性荧光,猝灭原因主要为静态猝灭和非辐射能量转移作用。胡椒酸乙酯对BSA的猝灭速率常数Kq为1.451×1013L.mol-1.s-1(25℃)和1.136×1013L.mol-1.s-1(37℃),胡椒酸乙酯与BSA的结合常数KA为9.484×105L.mol-1(25℃)和1.355×106L.mol-1(37℃),结合位点数n为1.18(25℃)和1.24(37℃)。根据Frster偶极-偶极非辐射能量转移理论得到结合距离r为2.68 nm(25℃)和2.81 nm(37℃)。通过热力学参数的计算,确定胡椒酸乙酯与牛血清白蛋白的相互作用是熵增加和吉布斯自由能降低的自发过程,主要作用力为疏水作用力。讨论了共存金属离子对胡椒酸乙酯与BSA的相互作用的影响。

The Effect of Metal Ions on Interaction Between Ethyl Piperate and Bovine Serum Albumin

The interaction between ethyl piperate and bovine serum albumin (BSA) was deeply investigated by using fluorescence spectroscopy (FS). The experimental results showed that the ethyl piperate molecules quenched the intrinsic fluorescence of BSA by forming ethyl piperate-BSA complex. The mechanism of fluorescence quenching was confirmed combining by both static quenching and non-radiation energy transferring. The quenching constants (Kq) are 1.451×1013 L·mol-1·s-1(25 ℃) and 1.136×1013 L·mol-1·s-1 (37 ℃). The apparent binding constants (KA) between ethyl piperate and BSA are 9.484×105 L·mol-1 (25 ℃) and 1.355×106 L·mol-1(37 ℃), and the value of binding sites (n) are 1.18(25 ℃) and 1.24(37 ℃). According to the Frster theory of non-radiation energy transfer, the binding distances (r) were 2.68 nm (25 ℃) and 2.81 nm (37 ℃). The process of binding was a spontaneous molecular interaction in which entropy increased and Gibbs free energy decreased, indicating that the interaction of ethyl piperate and BSA was driven mainly by hydrophobic force. The effects of metal ions on the interaction of ethyl piperate with BSA were also discussed.