There is an increasing awareness that a quantitative understanding of the cellular machinery requires considerable advancement of our current understanding of concentrated (or crowded) protein mixtures present in the cytosol. The main objective of this project is thus to measure and understand intermolecular interactions in concentrated protein solutions and mixtures as well as their dynamics. We use a combination of different scattering methods (SANS, SAXS, Static and Dynamic Light Scattering, Neutron Spin Echo (NSE) experiments), and compare the results with the predictions from numerical simulations. We in particular focus on the influence of interactions and their anisotropy on the diffusion of proteins. We can show that incorporating patchiness and thus interaction anisotropy has a dramatic effect on the dynamics and shifts the simulation results significantly towards matching our experimental results on the local short time dynamics of concentrated solutions of one of the lens proteins obtained from NSE.

In order to reach quantitative agreement with experiments at all volume fractions, we optimize our model by incorporating information based on the molecular structure of the protein. We use this refined anisotropic interaction potential as a starting point for simulating binary protein mixtures and comparing with data from NSE experiments and structural investigations.

People: Saskia Bucciarelli, Tommy Garting, Marc Obiols-Rabasa, Johan Bergenholtz, Bela Farago (ILL Grenoble, France), Olaf Holderer (Jülich Centre for Neutron Science (JCNS), Germany), Jin Suk Myung (FZ Jülich, Germany), Gerrit Vliegenthart (FZ Jülich), Roland Winkler (FZ Jülich), Gerhard Gompper (FZ Jülich), Jan Dhont (FZ Jülich), George Thurston (Rochester Institute of Technology, USA), Mikael Lund, Sara Linse, Peter Schurtenberger, Anna Stradner.

Contact person: Anna Stradner