Measuring Macromolecular Size-Distributions and Interactions at High Concentrations

Authors

• SK Chaturvedi
• J Ma
• PH Brown
• H Zhao
• P Schuck

Abstract

In concentrated macromolecular solutions, weak physical interactions control the solution behavior such as particle size distribution, stability, reversible oligomerization, aggregation, liquid-liquid phase separation, or crystallization. This is central to many fields ranging from colloid chemistry to cell biology and pharmaceutical protein engineering. Unfortunately it is very difficult to determine macromolecular assembly states and polydispersity at high concentrations in solution, since all motion is coupled through long-range hydrodynamic, electrostatic, steric, and other interactions, and scattering techniques report on the solution structure with interparticle distances comparable to macromolecular dimensions. Here we present a sedimentation velocity technique that can determine macromolecular size-distributions while simultaneously measuring mutual interactions through a nonideality parameter related to the average inter-particle potential and distance distribution. It offers high resolution and sensitivity up to 50 mg/ml of protein, extending studies of macromolecular solution state closer to the concentration range of therapeutic formulations, serum, or intracellular conditions.

Scientific Focus Area: Biomedical Engineering and Biophysics

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