Abstract
We have investigated liquid-liquid and solid-liquid phase separation of aqueous solutions of lysozyme. We have determined experimentally how the phase transition temperatures depend on protein concentration and the ionic composition of the solution. For a wide range of solution conditions, we find that the cloud-point temperature —which signals the onset of liquid-liquid phase separation—is 15–45 °C below the crystallization temperature . This indicates that liquid-liquid phase separation occurs in a highly metastable solution. When a series of chloride, bromide, and sulfate salts are added to lysozyme, we find that varies by as much as 60 °C over the salt concentration range of 0.2M to 1.5M. The precise change in depends sensitively on the identities of both the cation and the anion of the added salt. The effect of salts on is very similar to their effect on . The Derjaguin-Landau-Verwey-Overbeek theory for the interaction energy between charged spheres cannot account for our observations and indicates that hydration forces play an important role in protein interactions. © 1996 The American Physical Society.
- Received 16 October 1995
DOI:https://doi.org/10.1103/PhysRevE.53.6325
©1996 American Physical Society