Growth of Clusters toward Liquid-Liquid Phase Separation of Monoclonal Antibodies as Characterized by Small-Angle X-ray Scattering and Molecular Dynamics Simulation.

In concentrated protein solutions, short-range attractions (SRAs) contribute to liquid-liquid phase separation (LLPS) as a function of temperature and salinity, particularly when the charge and thus long-range repulsions are low near the isoelectric point pI. Herein, we study how SRA and solution morphology vary with the approach to LLPS from increased SRA for two monoclonal antibodies (mAbs) as salt concentration is reduced near the pI. These properties are quantified using small-angle X-ray scattering (SAXS) interpreted via coarse-grained (CG) molecular dynamics (MD) simulations and compared with less descriptive properties from static and dynamic light scattering.