Versatile Capillary Cells for Handling Concentrated Samples in Analytical Ultracentrifugation

Area of Science:

• Biophysics
• Materials Science
• Physical Chemistry

Background:

• Intermolecular interactions in concentrated macromolecular dispersions govern phase behavior.
• Studying these systems using analytical ultracentrifugation-sedimentation equilibrium (AUC-SE) is challenging due to limitations in current experimental setups.
• Existing methods often suffer from low success rates and handling difficulties.

Purpose of the Study:

• To introduce a novel, versatile capillary-cell design for AUC-SE optimized for high-concentration samples.
• To overcome the limitations of current AUC-SE cell designs for studying complex dispersions.
• To provide an easy-to-use, robust, and reusable tool for investigating macromolecular interactions and phase behavior.

Main Methods:

• Development of a capillary-cell with integrated liquid reservoirs fabricated via laser ablation or mechanical drilling.
• Tunable channel length and optical path length for customized measurements.
• Application of the cell to study concentrated gold nanoparticle dispersions, protein solutions (BSA, lysozyme), DNA solutions, and polymer mixtures (BSA/PEG).

Main Results:

• Demonstrated the cell's practicality for determining equations of state and second virial coefficients of concentrated dispersions.
• Successfully analyzed gelation phase transitions in DNA and BSA solutions.
• Investigated liquid-liquid phase separation in concentrated BSA/polyethylene glycol (PEG) droplets.
• Achieved a near 100% success rate in cell assembly and experimental reliability.

Conclusions:

• The novel capillary-cell design significantly enhances the study of concentrated macromolecular systems using AUC-SE.
• This versatile and robust tool facilitates reliable investigation of phase transitions, interactions, and phase separation.
• The design offers a significant improvement in experimental success rates and ease of use for researchers in biophysics and materials science.