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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1992 Feb 15;89(4):1214–1218. doi: 10.1073/pnas.89.4.1214

Solid-liquid phase boundaries of lens protein solutions.

C R Berland 1, G M Thurston 1, M Kondo 1, M L Broide 1, J Pande 1, O Ogun 1, G B Benedek 1
PMCID: PMC48419  PMID: 1741375

Abstract

We report measurement of the solid-liquid phase boundary, or liquidus line, for aqueous solutions of three pure calf gamma-crystallin proteins: gamma II, gamma IIIa, and gamma IIIb. We also studied the liquidus line for solutions of native gamma IV-crystallin calf lens protein, which consists of 85% gamma IVa/15% gamma IVb. 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 greater than 70 degrees C: gamma IIIa and gamma IV, and those in which liquidus lines flatten at temperatures less than 50 degrees C: gamma II and gamma IIIb. We have analyzed the form of the liquidus lines by using specific choices for the structures of the Gibbs free energy in solution and solid phases. By applying the thermodynamic conditions for equilibrium between the two phases to the resulting chemical potentials, we can estimate the temperature-dependent free energy change upon binding of protein and water into the solid phase.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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