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运用荧光光谱、紫外-可见吸收光谱和圆二色谱法研究了双十二烷基二甲基溴化铵(DDAB)与牛血红蛋白(Hb)的相互作用。从紫外-可见吸收光谱观察到,随着DDAB的浓度增大,Hb在406nm处的特征吸收峰强度下降,且峰位蓝移,说明DDAB导致血红素辅基微观环境变化。由荧光光谱研究可以得出随着DDAB的浓度增大,Hb在340nm处的荧光强度逐渐增强,说明导致色氨酸荧光淬灭的血红素辅基与色氨酸的距离增大。由Scatchard方程计算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DDAB与Hb之间以疏水作用力为主。圆二色谱的研究进一步表明DDAB使Hb产生轻微的二级结构改变,α-螺旋含量增加.
The interaction between DDA and bovine hemoglobin (Hb) was studied by fluorescence spectroscopy, UV-Vis absorption spectroscopy and circular dichroism spectroscopy. From the UV-Vis absorption spectra, the characteristic absorption peak intensity of Hb at 406 nm decreases with the increase of DDAB concentration, and the blue shift of the peak position indicates that DDAB leads to the change of heme prosthetic microenvironment. Fluorescence spectroscopy study shows that as the concentration of DDAB increases, the fluorescence intensity of Hb at 340 nm gradually increases, indicating that the distance between tryptophan and tryptophan resulting from tryptophan fluorescence quenching increases. The apparent binding constants, the number of binding sites and the thermodynamic parameters of the reaction at different temperatures were calculated by the Scatchard equation. The changes of the thermodynamic parameters indicated that the hydrophobic interaction between DDAB and Hb was dominant. Circular dichroism studies further indicate that DDAB causes minor secondary structural changes in Hb with an increase in alpha-helix content.