Interactions in protein solutions close to liquid-liquid phase separation: Ethanol reduces attractions via changes of the dielectric solution properties

Abstract

Ethanol is a common protein crystallization agent, precipitant, and denaturant, but also alters the dielectric properties of solutions. While ethanol-induced unfolding is largely ascribed to its hydrophobic parts, its effect on protein phase separation and inter-protein interactions remains poorly understood. Here, the effects of ethanol and NaCl on the phase behavior and interactions of protein solutions are studied in terms of the metastable liquid-liquid phase separation (LLPS) and the second virial coefficient $B_2$ using lysozyme solutions. Determination of the phase diagrams shows that the cloud-point temperatures are reduced and raised by the addition of ethanol and salt, respectively. The observed trends can be explained using the extended law of corresponding states as changes of $B_2$. The results for $B_2$ agree quantitatively with those of static light scattering and small-angle X-ray scattering experiments. Furthermore, $B_2$ values calculated based on inter-protein interactions described by the Derjaguin--Landau--Verwey--Overbeek (DLVO) potential and considering the dielectric solution properties and electrostatic screening due to the ethanol and salt content quantitatively agree with the experimentally observed $B_2$ values.

References in corpus (7)

• Extended corresponding-states behavior for particles with variable range attractions
• The Physics of Protein Self-Assembly
• Phase behaviour of a simple model of globular proteins
• A simple patchy colloid model for the phase behavior of lysozyme dispersions
• Extended law of corresponding states for protein solutions
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Cited by in corpus (4)

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• Phase separation and dynamical arrest of protein solutions dominated by short-range attractions
• Protein solutions close to liquid-liquid phase separation exhibit a universal osmotic equation of state and dynamical behavior
• Cluster Formation induced by local dielectric saturation in Restricted Primitive Model Electrolytes