桑色素与牛血红蛋白相互作用的光谱研究

利用紫外可见吸收光谱和荧光光谱研究了在生理pH条件下桑色素与牛血红蛋白(BHb)的相互作用。实验结果表明:桑色素分子与BHb发生反应生成基态复合物,导致BHb内源荧光的猝灭,该猝灭属于静态猝灭。测定了不同温度下该反应的表观结合常数、结合位点数及结合热力学参数,热力学参数的变化表明上述作用过程是一个熵增加、自由能降低的自发分子间作用过程,桑色素与BHb之间以疏水和静电作用力为主;根据F-rster能量转移理论,测得供体与受体间结合距离r和能量转移效率E;并用同步荧光光谱法探讨了桑色素对BHb构象的影响。

Studies on the Interaction between Morin and Bovine Hemoglobin (BHb) by Spectroscopic Methods

Morin is a bioactive plant flavonoid of immense importance as a potentially useful therapeutic drug. The interaction between morin and bovine hemoglobin (BHb) was investigated by UV/Vis absorption spectrum and fluorescence quenching spectroscopic methods. The experimental results showed that the fluorescence quenching of BHb by morin is a result of the formation of morin-BHb complex;static quenching was confirmed to result in the fluorescence quenching. The binding site number n(293 K: 1.11;308 K: 1.08),apparent binding constant KA (293 K:4.96 L·mol-1;308 K: 4.64 L·mol-1) and corresponding thermodynamic parameters (ΔHΘ=-3.34 kJ·mol-1;ΔGΘ=-26.34 kJ·mol-1/-27.51 kJ·mol-1;ΔSΘ=78.50 J·mol-1·K-1) were measured at two temperatures. The process of binding morin molecule on BHb was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. The binding distance r(r= 4.13 nm) and energy-transfer efficiency E(E=0.10) between morin and BHb were obtained according to fluorescence resonance energy transfer. The hydrophobic and electrostatic interactions play a major role in stabilizing the complex. The interaction of morin with BHb does not obviously affect the conformation of tryptophan and tyrosine micro-region of BHb. Thus,the results provided a quantitative understanding of the binding of morin to BHb,which is important in understanding its effect as therapeutic agent in therapy.