A modified Poisson-Boltzmann equation applied to protein adsorption

Area of Science:

• Physical Chemistry
• Biophysical Chemistry
• Surface Science

Background:

• Ion-exchange chromatography is vital for protein purification and analysis.
• Existing models have limitations in thermodynamically describing protein adsorption behavior.
• Understanding protein-surface electrostatic interactions is crucial.

Purpose of the Study:

• To develop an improved methodology for predicting protein adsorption equilibrium constants.
• To incorporate dispersion interactions and describe Hofmeister effects in protein adsorption.
• To provide a more accurate thermodynamic description of protein-surface interactions.

Main Methods:

• Solving a modified Poisson-Boltzmann equation in bispherical coordinates.
• Modeling protein-surface interactions as a spherical colloid-plate system.
• Calculating the protein-surface potential of mean force and Henry's adsorption constants.

Main Results:

• The modified Poisson-Boltzmann equation successfully describes Hofmeister effects by including ion-protein and ion-surface dispersion interactions.
• Henry's adsorption constants were accurately calculated as a function of pH, salt concentration, salt type, and temperature.
• The predicted Henry constants showed excellent agreement with experimental isotherm data.

Conclusions:

• The developed methodology provides a robust framework for predicting protein adsorption equilibrium constants.
• The inclusion of dispersion forces and the modified Poisson-Boltzmann equation enhance the description of protein-surface interactions.
• This work offers valuable insights for optimizing protein purification and analysis processes.