Analysis of the Statistical Thermodynamic Model for Nonlinear Binary Protein Adsorption Equilibria

Abstract

The statistical thermodynamic (ST) model was used to study nonlinear binary protein adsorption equilibria on an anion exchanger. Single-component and binary protein adsorption isotherms of bovine hemoglobin (Hb) and bovine serum albumin (BSA) on DEAE Spherodex M were determined by batch adsorption experiments in 10 mM Tris-HCl buffer containing a specific NaCl concentration (0.05, 0.10, and 0.15 M) at pH 7.40. The ST model was found to depict the effect of ionic strength on the single-component equilibria well, with model parameters depending on ionic strength. Moreover, the ST model gave acceptable fitting to the binary adsorption data with the fitted single-component model parameters, leading to the estimation of the binary ST model parameter. The effects of ionic strength on the model parameters are reasonably interpreted by the electrostatic and thermodynamic theories. The effective charge of protein in adsorption phase can be separately calculated from the two categories of the model parameters, and the values obtained from the two methods are consistent. The results demonstrate the utility of the ST model for describing nonlinear binary protein adsorption equilibria.

Molecular Dynamics Simulations of a Binary Protein Mixture Adsorption onto Ion-Exchange Adsorbent

“…Two protein molecules are placed into the liquid phase. The simulation box is further filled with water particles to represent a density of 1 g/cm 3 . In addition, 1088 chloride ions are added to keep the system electrically neutral.…”

Competitive Protein Adsorption to Soft Polymeric Layers: Binary Mixtures and Comparison to Theory

“…These authors stated that adsorption at equilibrium is mainly based on protein size discrimination, and is only partially related to the protein adsorption kinetics . Finally, recent models treat the adsorption process with different statistical mechanical routes which directly include the effect of the interactions within the system. − For example, Fang and Szleifer used the dynamic density functional theory (dDFT) explicitly including the size, shape, and charge distributions in all molecular species to describe protein adsorption kinetics on charged planar surfaces . Zhou et al studied the adsorption of binary mixtures of bovine hemoglobin and serum albumin onto an anion exchanger .…”

“…Finally, recent models treat the adsorption process with different statistical mechanical routes which directly include the effect of the interactions within the system. − For example, Fang and Szleifer used the dynamic density functional theory (dDFT) explicitly including the size, shape, and charge distributions in all molecular species to describe protein adsorption kinetics on charged planar surfaces . Zhou et al studied the adsorption of binary mixtures of bovine hemoglobin and serum albumin onto an anion exchanger . Adsorption isotherms in this case were fitted using a statistical thermodynamics approach based on model parameters which represent the interaction strength of the proteins and surface and between two proteins.…”

“…34 Zhou et al studied the adsorption of binary mixtures of bovine hemoglobin and serum albumin onto an anion exchanger. 37 Adsorption isotherms in this case were fitted using a statistical thermodynamics approach based on model parameters which represent the interaction strength of the proteins and surface and between two proteins. The proteins in this model are regarded as hard spheres with additional shortrange attractive interactions.…”

Ion‐Exchange Adsorption of Proteins: Experiments and Molecular Dynamics Simulations

“…This was the first study of adsorption isotherms of binary protein mixtures. Zhou [13] analyzed the effect of the ionic strength on the binary adsorption isotherms. Aboudzadeh [14] studied the importance of protein sizes and the interactions among different proteins in binary adsorption.…”