8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P10.37Protein-protein interactions - the effects of cosolvents,crowding and pressureRoland Winter 11 TU Dortmund, Otto Hahn Straße 6, 44227, Dortmund, GermanyThe effects of various kosmotropic and chaotropic cosolvents on the intermolecular interaction potentialof proteins (e.g., lysozyme) were evaluated at low to high protein concentrations by usingsynchrotron small-angle X-ray scattering in combination with liquid state theoretical approachesand FTIR-spectroscopy. The experimentally derived static structure factors obtained were analyzedwith a statistical mechanical model based on the DLVO potential which accounts for repulsive andattractive interactions. Supplementary thermodynamic information was obtained by employingcalorimetric techniques, densitometry and ultrasound velocimetry. Different cosolvents and saltsinfluence the interactions between protein molecules differently as a result of changes in the hydrationlevel, charge screening, specific adsorption of the additives at the protein surface, hydrophobicinteractions, or solvent structure. Experimentally derived static structure factors were alsoobtained for aggregation-prone proteins. The data reveal that the protein self-assembles into equilibriumclusters already at relatively low concentrations. Striking differences regarding interactionforces between aggregation-prone proteins such as insulin in the pre-aggregated regime and nativelystable globular proteins are found. Finally, to probe also extreme environmental conditions,the effects of crowding and pressure on the solvational properties and intermolecular interaction ofthe proteins were studied, and a tentative temperature-concentration-pressure phase diagram couldbe obtained.37