Measuring macromolecular size distributions and interactions at high concentrations by sedimentation velocity

• Published in: Nature communications 2018-10, Vol.9 (1), p.4415-9, Article 4415
• Main Authors: Chaturvedi, Sumit K., Ma, Jia, Brown, Patrick H., Zhao, Huaying, Schuck, P.
• Format: Article
• Language: English
• Subjects: 631/1647; 639/166/898; 639/638/440; 639/766/747; Algorithms; Colloid chemistry; Crystallization; Electrostatic properties; Formulations; Humanities and Social Sciences; Hydrodynamics; Liquid phases; Macromolecular Substances - chemistry; Macromolecules; multidisciplinary; Organic chemistry; Particle size distribution; Phase separation; Polydispersity; Protein engineering; Proteins; Proteins - chemistry; Science; Science (multidisciplinary); Sedimentation; Sedimentation & deposition; Size distribution; Velocity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-06902-x

In concentrated macromolecular solutions, weak physical interactions control the solution behavior including particle size distribution, 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 when average interparticle distances are comparable to macromolecular dimensions. Here we present a sedimentation velocity technique that, for the first time, can resolve macromolecular size distributions at high concentrations, by simultaneously accounting for average mutual hydrodynamic and thermodynamic interactions. It offers high resolution and sensitivity of protein solutions up to 50 mg/ml, extending studies of macromolecular solution state closer to the concentration range of therapeutic formulations, serum, or intracellular conditions. Many aspects of concentrated macromolecular solutions, such as encountered in cytosol or in pharmaceutical formulations, are dependent on particle size distributions and weak intermolecular interactions. Here, the authors exploit hydrodynamic separation in the centrifugal field to measure both.