Generic pathways to stability in concentrated protein mixtures

Ilja K. Voets; Veronique Trappe; Peter Schurtenberger

doi:10.1039/C2CP22558A

Generic pathways to stability in concentrated protein mixtures

Ilja K. Voets,*^a^b Veronique Trappe^c and Peter Schurtenberger^b^d

* Corresponding authors

^a Institute for Complex Molecular Systems and Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
E-mail: i.voets@tue.nl

^b Adolphe Merkle Institute, University of Fribourg, P.O. Box 209, CH-1723 Marly 1, Switzerland

^c Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700 Fribourg, Switzerland

^d Division of Physical Chemistry, Center for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden

Abstract

We present a series of experimental results that disclose the crucial role of ionic strength and partial volume fractions in the control of the phase behaviour of binary protein mixtures. Our findings can be understood as that the ionic strength determines the relative contribution of the entropy of the protein counter-ions to the overall thermodynamics of the system. Associative phase separation and crystallization observed at, respectively, low and high ionic strength are suppressed at intermediate salt concentrations, where the entropy gain upon releasing the counter-ions from the double layer of the proteins is negligible and the entropy loss upon confining the counter-ions within the protein crystal phase significant. Moreover, we find that the partial volume fraction of the protein prone to crystallize determines the crystallization boundary and that the presence of other proteins strongly delays crystallization, leading to temporarily stable mixtures. These findings suggest that stability in more complex protein mixtures, such as the cytosol, relates to the ionic strength and protein composition rather than to protein specific properties.

Supplementary files

Publication details

The article was received on 08 Aug 2011, accepted on 12 Dec 2011 and first published on 19 Jan 2012

Article type: Paper

DOI: 10.1039/C2CP22558A

Citation: Phys. Chem. Chem. Phys., 2012,14, 2929-2933

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Generic pathways to stability in concentrated protein mixtures

I. K. Voets, V. Trappe and P. Schurtenberger, Phys. Chem. Chem. Phys., 2012, 14, 2929
DOI: 10.1039/C2CP22558A
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Physical Chemistry Chemical Physics

Generic pathways to stability in concentrated protein mixtures

Abstract

Supplementary files

Publication details

Generic pathways to stability in concentrated protein mixtures

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