Hajra S, Chattoraj D K
Department of Food Technology and Biochemical Engineering, Jadavpur University, Calcutta.
Indian J Biochem Biophys. 1991 Aug;28(4):267-79.
Adsorption isotherms of BSA at the solid-water interfaces have been studied as a function of protein concentration, ionic strength of the medium, pH and temperature using silica, barium sulphate, carbon, alumina, chromium, ion-exchange resins and sephadex as solid interfaces. In most cases, isotherms for adsorption of BSA attained the state of adsorption saturation. In the presence of barium sulphate, carbon and alumina, two types in the isotherms are observed. Adsorption of BSA is affected by change in pH, ionic strength and temperature of the medium. In the presence of metallic chromium, adsorbed BSA molecules are either denatured or negatively adsorbed at the metallic interface. Due to the presence of pores in ion-exchange resins, adsorption of BSA is followed by preferential hydration on resin surfaces in some cases. Sometimes two steps of isotherms are also observed during adsorption of BSA on the solid resins in chloride form. Adsorption of BSA, beta-lactoglobulin, gelatin, myosin and lysozyme is negative on Sephadex surface due to the excess adsorption of water by Sephadex. The negative adsorption is significantly affected in the presence of CaCl2, KSCN, LiCl, Na2SO4, NaI, KCl and urea. The values of absolute amounts of water and protein, simultaneously adsorbed on the surface of different solids, have been evaluated in some cases on critical thermodynamic analysis. The standard free energies (delta G0) of excess positive and negative adsorption of the protein per square meter at the state of monolayer saturation have been calculated using proposed universal scale of thermodynamics. The free energy of adsorption with reference to this state is shown to be strictly comparable to each other. The magnitude of standard free energy of transfer (delta G0B) of one mole of protein or a protein mixture at any type of physiochemical condition and at any type of surface is observed to be 38.5 kJ/mole.
已使用二氧化硅、硫酸钡、碳、氧化铝、铬、离子交换树脂和葡聚糖作为固体界面，研究了牛血清白蛋白（BSA）在固 - 水界面的吸附等温线，考察其作为蛋白质浓度、介质离子强度、pH值和温度的函数关系。在大多数情况下，BSA的吸附等温线达到吸附饱和状态。在硫酸钡、碳和氧化铝存在的情况下，观察到等温线有两种类型。BSA的吸附受介质pH值、离子强度和温度变化的影响。在金属铬存在的情况下，吸附的BSA分子在金属界面处要么变性要么负吸附。由于离子交换树脂中存在孔隙，在某些情况下，BSA吸附后会在树脂表面发生优先水合作用。有时在BSA吸附到氯化物形式的固体树脂上的过程中也会观察到两步等温线。由于葡聚糖对水的过量吸附，BSA、β - 乳球蛋白、明胶、肌球蛋白和溶菌酶在葡聚糖表面的吸附为负吸附。在氯化钙、硫氰酸钾、氯化锂、硫酸钠、碘化钠、氯化钾和尿素存在的情况下，负吸附受到显著影响。在某些情况下，通过临界热力学分析评估了同时吸附在不同固体表面的水和蛋白质的绝对量值。使用提出的通用热力学标度计算了在单层饱和状态下每平方米蛋白质过量正吸附和负吸附的标准自由能（ΔG0）。相对于该状态的吸附自由能显示出彼此严格可比。在任何类型的物理化学条件和任何类型的表面上，一摩尔蛋白质或蛋白质混合物的标准转移自由能（ΔG0B）的大小为38.5 kJ/摩尔。
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