Solid-Liquid Phase Boundaries of Lens Protein Solutions

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-02, Vol.89 (4), p.1214-1218
• Main Authors: Berland, Carolyn R., Thurston, George M., Kondo, Mamoru, Broide, Michael L., Pande, Jayanti, Ogun, Olutayo, Benedek, George B.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cattle; Critical temperature; Crystallins; Crystallins - chemistry; Crystallography; Crystals; eye lens; Free energy; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; In Vitro Techniques; Kinetics; Liquidus; Melting; Molecular biophysics; Molecules; Physico-chemical properties of biomolecules; Proteins; Solid phases; Solutions; Temperature; Thermodynamic equilibrium; Thermodynamics; Water
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.4.1214

We report measurement of the solid-liquid phase boundary, or liquidus line, for aqueous solutions of three pure calf γ-crystallin proteins: γII, γIIIa, and γIIIb. We also studied the liquidus line for solutions of native γIV-crystallin calf lens protein, which consists of 85% γIVa/15% γIVb. In all four proteins the liquidus phase boundaries lie higher in temperature than the previously determined liquid-liquid coexistence curves. Thus, over the range of concentration and temperature for which liquid-liquid phase separation occurs, the coexistence of a protein crystal phase with a protein liquid solution phase is thermodynamically stable relative to the metastable separated liquid phases. The location of the liquidus lines clearly divides these four crystallin proteins into two groups: those in which liquidus lines flatten at temperatures >70⚬C: γIIIa and γIV, and those in which liquidus lines flatten at temperatures