Studying Crowding Dynamics in Concentrated Protein Solutions With XPCS

Eukaryotic cells provide highly concentrated environments containing a variety of different molecular components with specific functions. Diffusion dynamics of proteins in such crowded environments are crucial for biological processes and are strongly affected by molecular interactions and the microscopic environment. Molecular crowding can dramatically alter molecular motion and thus influence the biological function of proteins. A case in point is the theoretically predicted slowing down of the protein dynamics due to the formation of local transient clusters. Making use of the superior coherence properties of the ESRF-EBS we propose here to study crowding effects in highly concentrated apoferritin solutions with Polyethylene glycol as a crowding agent by XPCS. We will systematically measure the q-dependence and concentration dependence of the diffusion constants and other dynamic parameters to determine the molecular details of the diffusion dynamics in crowded protein solutions.