甲钴胺与牛血清白蛋白相互作用的光谱特性

应用荧光光谱法、紫外吸收光谱法及共振光散射法,研究了甲钴胺 (Mecobalamin) 与牛血清白蛋白 (BSA) 之间的相互作用。在pH=7.40的三羟甲基胺基甲烷-盐酸 (Tris-HCl) 缓冲溶液中,随着甲钴胺浓度的增加,BSA的荧光强度、共振散射光强度逐渐减弱。通过计算不同温度(293,303,310 K)下的猝灭常数 (K_sv=5.40×10⁴,6.90×10⁴,8.00×10⁴ L/mol) 及扫描紫外吸收光谱,确定了甲钴胺对牛血清白蛋白的猝灭机理为动态猝灭。测定了该反应的表观结合常数 (K_A=1.68×10⁴,4.34×10⁴,7.90×10⁴ L/mol)和结合位点数 (n≈1)。利用热力学参数 (ΔH>0、ΔG<0和ΔS>0) 确定了分子间的作用力性质,作用力主要是疏水作用力,作用过程是自发的。同时应用同步荧光技术研究了甲钴胺对BSA构象的影响。结果表明,甲钴胺没有引起BSA构象的变化。

Spectroscopic Studies on The Interaction Between Mecobalamin and Bovine Serum Albumin

The interaction of mecobalamin and bovine serum albumin(BSA) was studied by fluorescence spectroscopy,ultraviolet absorption spectroscopy and resonance light scattering spectroscopy.The results showed that in pH 7.40 Tris-HCl buffer solution,both the fluorescence and resonance light scattering intensity were quenched when increasing the mecobalamin concentration.According to Stern-Volmer curve,the fluorescence quenching constant was calculated(Ksv=5.40×104,6.90×104,8.00×104 L/mol) with the interaction of mecobalamin and BSA at different temperatures(293,303,310 K).At the same time,ultraviolet absorption spectra were characterized.The experimental results indicated that the fluorescence quenching mechanism of mecobalamin with BSA was a dynamic quenching procedure.The binding constants(KA=1.68×104,4.34×104,7.90×104 L/mol),binding sites(n≈1) and the corresponding thermodynamic parameters,namely enthalpy change(ΔH),free energy change(ΔG) and entropy change(ΔS) at different temperatures were calculated(ΔH>0,ΔG<0,and ΔS>0).According to the thermodynamic parameters,during the binding process,spontaneous molecular interaction occurs in which entropy increased and free energy decreased.These indicate the hydrophobic interaction was the main sort of binding force between the reaction of mecobalamin and BSA.In addition,the effect of mecobalamin on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy.The results revealed that mecoba-lamin did not change the conformation of BSA during the reaction.