Effect of Buffer on Protein Stability in Aqueous Solutions: A Simple Protein Aggregation Model

Area of Science:

• Biophysics
• Protein Chemistry
• Computational Biology

Background:

• Liquid-liquid phase separation (LLPS) is linked to various diseases.
• Buffer effects on protein aggregation are often overlooked in LLPS studies.

Purpose of the Study:

• Investigate buffer influence on hen egg-white lysozyme (HEWL) phase stability and protein-protein interactions.
• Develop a coarse-grained model incorporating buffer-specific effects for predicting protein aggregation.

Main Methods:

• Measured cloud point temperature, second virial coefficient, and interaction diffusion coefficient for HEWL in different buffers (MOPS, phosphate, HEPES, cacodylate) at pH 7.0.
• Extended a coarse-grained protein model using Wertheim's perturbation theory to include buffer effects.

Main Results:

• Buffer molecules adsorb onto protein surfaces, modulating electrostatic stability and influencing phase separation.
• The developed model accurately predicted experimental phase separation for HEWL-buffer solutions.
• The model can predict phase stability under conditions not experimentally accessible.

Conclusions:

• Buffer composition is a critical factor in protein LLPS and aggregation.
• The enhanced coarse-grained model provides a robust tool for studying protein aggregation in complex biological systems.
• This approach aids in understanding and predicting protein behavior in cellular environments.