Theory for electrostatic interaction chromatography of proteins

Area of Science:

• Biochemistry
• Physical Chemistry
• Chromatography

Background:

• Ion-exchange chromatography is crucial for protein separation.
• Understanding the impact of eluent salt concentration on protein retention is key.
• Existing models like stoichiometric displacement have limitations.

Purpose of the Study:

• To develop a simple theoretical framework for protein retention in ion-exchange chromatography.
• To establish a relationship between eluent salt concentration and retention factor.
• To provide a method for estimating protein charges from chromatographic data.

Main Methods:

• Solving the linearized Poisson-Boltzmann equation for charged surfaces.
• Analyzing protein retention data using a logarithmic scale against the reciprocal square root of ionic strength.
• Comparing chromatographically derived protein charges with titrimetric measurements.

Main Results:

• A linear correlation was predicted and observed between the logarithm of the retention factor (ln k') and the reciprocal square root of ionic strength (1/√I).
• The theoretical model demonstrated good agreement with experimental retention data across various conditions.
• Estimated protein charges from chromatography correlated well with titrimetric results.

Conclusions:

• The proposed theoretical framework offers a realistic and convenient method for analyzing protein retention in ion-exchange chromatography.
• The model accurately predicts the effect of salt concentration on protein retention.
• This approach facilitates the estimation of protein characteristic charges using fundamental constants.