Analysis of the statistical thermodynamic model for nonlinear binary protein adsorption equilibria

Area of Science:

• Biophysical Chemistry
• Separation Science
• Protein Chemistry

Background:

• Understanding protein adsorption is crucial for bioseparations and biomaterial development.
• Nonlinear adsorption equilibria and ionic strength effects complicate protein binding predictions.

Purpose of the Study:

• To evaluate the statistical thermodynamic (ST) model for nonlinear binary protein adsorption.
• To investigate the influence of ionic strength on protein adsorption equilibria.
• To determine protein effective charge during adsorption.

Main Methods:

• Batch adsorption experiments were conducted using bovine hemoglobin (Hb) and bovine serum albumin (BSA) on DEAE Spherodex M.
• Adsorption isotherms were measured at varying NaCl concentrations (0.05-0.15 M) and pH 7.40.
• The ST model was applied to fit single-component and binary adsorption data.

Main Results:

• The ST model effectively described single-component protein adsorption, with parameters sensitive to ionic strength.
• The model provided acceptable fits for binary protein adsorption, allowing estimation of binary interaction parameters.
• Ionic strength effects on model parameters were explained by electrostatic and thermodynamic principles.
• Consistent effective protein charges were calculated using different model parameter categories.

Conclusions:

• The statistical thermodynamic model is a valuable tool for describing nonlinear binary protein adsorption equilibria.
• Ionic strength significantly impacts protein adsorption behavior and effective charge.
• The ST model provides insights into the electrostatic and thermodynamic driving forces of protein adsorption.