Analytical ultracentrifugation in a Gibbsian perspective

Area of Science:

• Biophysical chemistry
• Macromolecular science
• Analytical chemistry

Background:

• Analytical ultracentrifugation (AUC) is experiencing a resurgence due to instrumental and computational advancements.
• Current AUC focuses on macromolecule interactions in various systems.
• Biological systems often contain charged cosolvents that influence solute behavior.

Purpose of the Study:

• To highlight the quantitative impact of solvent/cosolvent interactions on solute/solute interactions in AUC.
• To propose a more comprehensive thermodynamic approach for AUC data analysis.

Main Methods:

• Re-evaluation of the Svedberg equation's applicability.
• Application of classical thermodynamic principles for density increment and osmotic pressure derivatives.
• Analysis of multicomponent systems including charged and non-charged cosolvents.

Main Results:

• The traditional Svedberg derivation is limited to ideal, two-component systems at vanishing concentrations.
• Solvent/cosolvent interactions significantly influence the measured solute/solute interactions.
• A thermodynamic approach using density increment and osmotic pressure derivatives offers a more accurate analysis.

Conclusions:

• Comprehensive AUC analysis must account for solvent/cosolvent and solute/cosolvent interactions.
• The proposed thermodynamic method provides a more accurate assessment of macromolecular interactions in complex biological solutions.
• Future AUC studies should incorporate these interactions for precise quantitative results.