Dynamics of vesicles in dense pools studied by XPCS

We propose to study the dynamics of synaptic vesicles (SV) [1] and of artificial lipid vesicles in dense vesicle pools by XPCS. Pools are aggregates of vesicles which are clustered together by proteins causing an attractive interaction. We target in particular the short range (hindered) diffusion of vesicles which are believed to be at least partially arrested in the pool. Center-of-mass movements as well as relaxation of deformations and viscoelastic strain fields in the pool are expected to contribute to the XPCS signal, and will be disentangled via the q-dependence and by varying the sample setup (density, SV versus simple vesicles, protein concentration etc.). Here we extend our previous SAXS study of SV pools (SC-5112) by X-ray photon correlation spectroscopy (XPCS) using highly brilliant ESRF undulator radiation. We want to understand how a vesicle diffuses within a dense cluster which is formed by gel-like interaction with specific proteins, notably synapsin.