基于光波导分光光谱技术研究蛋白质与亚甲基蓝的竞争吸附行为

通过利用时间分辨光波导分光光谱技术原位测量从蛋白质-亚甲基蓝(MB)混合水溶液吸附到亲水玻璃光波导表面的MB可见光吸收谱,观测到在溶液pH值低于蛋白质等电点时MB与牛血清蛋白(BSA)以及MB与血红蛋白(Hb)存在竞争吸附行为,进一步测得这种竞争吸附行为对蛋白质浓度十分敏感,可以用于简单测定溶液中的蛋白质含量.基于Langmuir等温吸附理论推导出了两种分子竞争吸附的动力学方程,并利用该动力学方程对实验测得的吸光度随时间变化曲线进行了最佳拟合,揭示了玻璃表面吸附的MB分子个数在达到最大值后随时间呈指数衰减,同时得出拟合参数与蛋白质浓度呈准线性关系.

Study of Competitive Adsorption Behavior of Protein and Methylene Blue by Optical Waveguide Spectroscopy

We used time-resolved optical waveguide spectroscopy (OWGS) to in-situ measure visible absorption spectrum for methylene blue (MB) adsorbed ona hydrophilic glass waveguide from an aqueous solution containing proteins such as bovine serum albumin (BSA) and hemoglobin (Hb). The competitive adsorption of MB and the protein was detected at a solution pH lower than the isoelectric point of the protein. Since the competitive adsorption behavior of MB and the protein is very sensitive to the protein concentration, the protein content in the mixed solution was readily determined by time-resolved OWGS. In addition, a kinetic equation for the competitive adsorption of the two molecules was deduced based on the Langmuir adsorption isotherm. The best fit of the measured time course of the absorbance with the theoretical kinetic equation reveals that the number of MB molecules adsorbed on the surface exponentially decreases with time after reaching a maximum.A quasi-linear relationship between the fitting parameters and the protein concentration was also obtained.