超声作用下稀土离子对纳米TiO2与牛血清白蛋白相互作用的影响

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和聚丙烯酰胺凝胶电泳(SDS-PAGE)研究了超声作用下三种稀土离子(La3+、Gd3+、Yb3+)存在的不同体系中,纳米TiO2与牛血清白蛋白(BSA)的相互作用.结果表明:在超声作用下,不同体系中纳米TiO2均导致BSA的内源荧光猝灭,其猝灭机制主要为静态猝灭和非辐射能量转移;凝胶电泳结果表明,不同体系中的纳米TiO2均未对BSA的结构造成明显的损伤,由热力学数据确定其作用力主要为氢键和范德华力.稀土离子的存在使纳米TiO2与BSA的结合常数、结合距离和热力学参数发生改变,但结合位点数和作用力类型基本不变.稀土离子对纳米TiO2与BSA的结合产生明显的"四分组效应",它们分别以"离子架桥"和"同位取代"方式参与纳米TiO2与BSA的结合过程.

Effects of Rare Earth Ions on the Interaction between Nano TiO2 and Bovine Serum Albumin in the Presence of Ultrasound

The effects of rare earth ions(La3+,Gd3+,Yb3+) on the interactions between nano TiO2 and bovine serum albumin(BSA) were investigated in the presence of ultrasound.A combination of ultraviolet(UV) spectroscopy,fluorescence spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE) were used to characterize the interactions under simulated human physiological conditions.The endogenous fluorescence of BSA was quenched by nano TiO2 in different systems.The mechanism of fluorescence quenching was static quenching with non-radiative energy transfer.SDS-PAGE revealed that the structure of BSA was not obviously destroyed upon binding with nano TiO2 in different systems.Hydrogen bond and van der Waals interaction were deduced,on the basis of the thermodynamic parameters,to be the major driving forces.The binding distance of nano TiO2 to BSA and the thermodynamic parameters were changed in the presence of rare earth ions.However,the number of binding sites and the type of intermolecular force remained essentially unchanged.This indicated that the interaction between nano TiO2 and BSA was influenced by the rare earth ions,and that a lanthanide tetrad effect was observed.It is conjectured that rare earth ions participate in the nano TiO2-BSA interaction process by means of "ionic bridge" formation or "appositional substitution".