肉苁蓉苷F与牛血清白蛋白相互作用的光谱学研究

目的:探讨咖啡酸类小分子肉苁蓉苷F与牛血清白蛋白的结合反应特性。方法:运用荧光光谱(FS)、紫外-可见光谱(UV)和圆二色谱(CD)法探讨了生理条件下肉苁蓉苷F(该化合物为作者首次从紫珠属植物中分离得到,简记为CF)与牛血清白蛋白(BSA)的相互作用。结果:计算得到CF-BSA的静态表观结合常数(Ka),结合位点数(n),能量转移效率(E),空间距离(r),热力学参数ΔG,ΔH,ΔS,与CF作用前后BSA中α-螺旋结构含量的变化,明确了CF在BSA上的结合位置,分析了几种常见金属离子对CF与BSA相互作用的影响。结论:CF与BSA形成基态复合物可导致BSA内源荧光猝灭,其在BSA上的结合位点数约为1,25℃时的结合常数Ka为4.36×104L·mol-1,二者之间的空间距离r为3.09 nm,结合过程主要表现为氢键作用,CF在BSA上的作用位点为site I,Mg2+,Fe3+,Cu2+,Zn2+的存在增强了CF与BSA的结合作用。猝灭机制主要为静态猝灭和非辐射能量转移。CD光谱表明CF对BSA的空间构型改变有一定的影响。

Spectroscopic study on interaction between cistanoside F and bovine serum albumin

Objective: To study the conjugation reaction characteristics of caffeic acid micromolecule cistanoside F and bovine serum albumin.Method: The interaction between bovine serum albumin(BSA) and cistanoside F that was separated from Callicarpa plant for the first time and abbreviated CF was detected by fluorescence(FS),UV-vis absorbance and circular dichroism(CD) under simulative physiological conditions.Result: CF-BSA′s static apparent binding constant(Ka),number of binding sites(n),efficiency of energy transfer(E),spatial distance(r),thermodynamic parameters ΔG,ΔH and ΔS and changes in α-helical structure content in BSA before and after CF′s effect were calculated to define the binding site of CF in BSA and analyze the impact of several common metal ions on the interaction of CF and BSA.Conclusion: Ground state compounds formed by CF and BSA could cause intrinsic fluorescence quenching.Their binding constant Ka of cistanoside F with BSA was 4.36×104 L·mol-1 at 25 ℃,the number of binding site n was 1,and the spatial distance r was 3.09 nm.The results indicated that the hydrogen bond played a major role in cistanoside F-BSA association.The displacement experiments confirmed that cistanoside F can bind to siteⅠof BSA.In addition,the binding constant of cistanoside F with BSA was enhanced after the addition of some common metal ions Mg2+,Fe3+,Cu2+ and Zn2+.The intrinsic fluorescence of BSA was quenched by cistanoside F via forming cistanoside F-BSA complex and non-radiation energy transfer.CD spectra showed that the binding of cistanoside F with BSA induced conformational changes in BSA.