铽离子探针法研究单宁酸与伴清蛋白相互作用

以pH 7.4、含有0.1 mol?L^－1 NaCl的0.01 mol?L^－1 Hepes为缓冲液, 在(25±0.2) ℃, 采用荧光光谱法研究了单宁酸(TA)与伴清蛋白(apoOTF)的相互作用. 由蛋白内源荧光测定表明: TA分别与apoOTF, Tb_N^3＋-apoOTF和Tb_N^3＋-apoOTF- Tb_C^3＋结合形成1∶1配合物, 其表观结合常数(K_A)分别为7.15×10⁵, 4.16×10⁶和3.77×10⁶ mol^－1?L. 以Tb^3＋敏化荧光测定表明：TA与Tb³⁺可形成1∶2配合物, 且TA与Tb³⁺的结合能力大于apoOTF与Tb³⁺的结合能力. TA-Tb₂^3＋配合物也可与该蛋白结合形成1∶1复合物, 其K_A为1.86×10⁵ mol^－1?L.

Investigation of the Interaction between Apoovotransferrin and Tannic Acid using Terbium Ions as Spectroscopic Probe.

The interactions between tannic acid (TA) and apoovotransferrin (apoOTF) were studied by fluorescence spectroscopy with the spectroscopic probes of Tb^3＋ and intrinsic fluorescence of the protein in 0.01 mol?L^－1 Hepes, at pH 7.4 and room temperature. The results showed that the complex with the molar ratio 1∶1 was formed between TA and apoOTF, Tb_N^3＋-apoOTF, Tb_N^3＋-apoOTF-Tb_C^3＋, respectively. The binding constants of TA to apoOTF, Tb_N^3＋-apoOTF and Tb_N^3＋-apoOTF-Tb_C^3＋ was 7.15×10⁵, 4.16×10⁶ and 3.77×10⁶ mol^－1?L, respectively. What’s more, the tannic acid could bind to terbium ions, whose binding molar ratio was about 1∶2, and the binding ability of Tb^3＋ to apoOTF was weaker than that of Tb^3＋ to the tannic acid. Moreover, binding constant for attachment of TA-Tb₂^3＋ to apoOTF was 1.86×10⁵ mol^－1?L, and the number of binding sites of the protein for TA-Tb₂^3＋ was about 1.