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

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  • Jan Hansen, Heinrich Heine University Düsseldorf
  • ,
  • Rajeevann Uthayakumar, Heinrich Heine University Düsseldorf
  • ,
  • Jan Skov Pedersen
  • Stefan U. Egelhaaf, Heinrich Heine University Düsseldorf
  • ,
  • Florian Platten, Heinrich Heine University Düsseldorf, Jülich Research Centre

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 coefficientB2using 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 ofB2. The results forB2agree quantitatively with those of static light scattering and small-angle X-ray scattering experiments. Furthermore,B2values 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 observedB2values.

Original languageEnglish
JournalPhysical Chemistry Chemical Physics
Pages (from-to)22384-22394
Number of pages11
Publication statusPublished - Oct 2021

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