贝诺酯与牛血清白蛋白位点选择性结合的分子光谱研究

采用荧光光谱、紫外可见光谱、同步荧光光谱及三维荧光光谱等分子光谱方法,研究了生理条件下贝诺酯(BEN)与牛血清白蛋白(BSA)的相互作用。结果表明,BEN对BSA的内源荧光有显著的猝灭作用,猝灭机理为动态猝灭,二者之间的作用力类型以疏水作用为主,BEN与BSA发生反应后,使BSA的疏水环境极性增强,疏水性减弱,荧光强度降低。测得的表观结合常数和结合位点数分别是1 050 L·mol^-1和0.88,同时测得了焓变(ΔH)、熵变(ΔS)和自由能变(ΔG)等热力学参数。同步荧光和三维荧光光谱的结果表明,BEN使BSA的构象发生改变。利用荧光特异性位点探针DA和DP,通过竞争结合实验,监测BEN与BSA的结合位点,测得了位点Ⅰ和位点Ⅱ的表观结合常数分别为4 300 L·mol^-1和21 200 L·mol^-1,表明BEN与BSA优先在位点Ⅱ结合。

Molecular Spectroscopic Study on Site-selective Binding of Benorilate to Bovine Serum Albumin

The interaction between benorilate(BEN) and bovine serum albumin(BSA) was investigated under physiological condition by molecular spectroscopic techniques,including fluorescence spectroscopy,UV-visible spectroscopy,synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy.The intrinsic fluorescence of tryptophan in BSA was significantly quenched by BEN via dynamic quenching.The hydrophobic interaction did favor the interaction of BSA with BEN.The apparent binding constants and binding sites number at the tryptophan site were 1 050 L·mol-1 and 0.88,respectively.Thermodynamic parameters such as enthalpy change(ΔH),entropy change(ΔS) and free energy change(ΔG) were also obtained.The conformation changes of BSA in the presence of BEN were proved by the evidences of synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy.Two site-specific fluorescence probes,dansylamide(DA) and dansyl-L-proline(DP),were employed in competitive binding experiments to monitor the BEN binding sites of BSA.The apparent binding constants at siteⅠand Ⅱ were 4 300 and 21 200 L· mol-1,respectively.