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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。
Objective: To investigate the binding reaction of cacoside F, a small molecule of caffeic acid, with bovine serum albumin. Methods: Cistanin glycosides F (the compound was isolated from the genus Ureaplasma for the first time, and was abbreviated as (2)) was studied by fluorescence spectroscopy (FS), UV- CF) with bovine serum albumin (BSA). Results: Static apparent binding constant (Ka), number of binding sites (n), energy transfer efficiency (E), spatial distance (r), thermodynamic parameters ΔG, ΔH and ΔS of CF-BSA were calculated. Α-helical structure changes in the content of clear CF in BSA binding position, analyzed several common metal ions on CF and BSA interaction. CONCLUSION: The formation of ground state complex between CF and BSA can lead to endogenous fluorescence quenching of BSA. The binding constant Ka of BSA with binding site of about 1,25 ℃ is 4.36 × 104 L · mol -1 The spatial distance r is 3.09 nm. The binding process is mainly hydrogen bonding, and the site of CF on BSA is site I. The presence of Mg2 +, Fe3 +, Cu2 + and Zn2 + enhances the binding of CF and BSA. Quenching mechanisms are mainly static quenching and non-radiative energy transfer. CD spectra show that CF has some influence on the spatial configuration of BSA.