Phase behavior of lysozyme solutions in the liquid–liquid phase coexistence region at high hydrostatic pressures

Abstract

We present results from small-angle X-ray scattering and turbidity measurements on the effect of high hydrostatic pressure on the phase behavior of dense lysozyme solutions in the liquid–liquid phase separation region, and characterize the underlying intermolecular protein–protein interactions as a function of temperature and pressure under charge-screening conditions (0.5 M NaCl). A reentrant liquid–liquid phase separation region is observed at elevated pressures, which may originate in the pressure dependence of the solvent-mediated protein–protein interaction. A temperature-pressure-concentration phase diagram was constructed for highly concentrated lysozyme solutions over a wide range of temperatures, pressures and protein concentrations including the critical region of the liquid–liquid miscibility gap.