Collective diffusion coefficient of proteins with hydrodynamic, electrostatic, and adhesive interactions

Area of Science:

• Physical Chemistry
• Colloid Science
• Biophysics

Background:

• Understanding protein diffusion is crucial for biophysical processes.
• Interactions like electrostatic and adhesive forces significantly influence protein behavior.
• Accurate modeling of diffusion coefficients requires accounting for hydrodynamic interactions.

Purpose of the Study:

• To develop a theoretical framework for lambdaC, the first-order correction to the collective diffusion coefficient for protein spheres.
• To investigate the impact of lubrication forces on diffusion using numerical analysis of Stokesian hydrodynamics.
• To propose and validate formulas for lambdaC based on effective stickiness.

Main Methods:

• Developed a theory for lambdaC considering electrostatic and adhesive forces between protein spheres.
• Performed extensive numerical analysis of two-sphere Stokesian hydrodynamics to quantify lubrication effects.
• Introduced an effective stickiness parameter to simplify lambdaC calculations.
• Derived both simple and elaborate approximations for lambdaC.

Main Results:

• A simple formula for lambdaC was derived using the effective stickiness parameter.
• A more elaborate, precise approximation for lambdaC was also developed.
• The theoretical expressions for lambdaC were compared with experimental data for lysozyme at pH 4.5 across various ionic strengths (0.05M-2M).

Conclusions:

• The developed theory and formulas provide accurate predictions for lambdaC.
• The study highlights the importance of lubrication forces in protein diffusion.
• The findings are validated by experimental data, improving our understanding of protein solution dynamics.