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DY: Fachverband Dynamik und Statistische Physik

DY 52: Statistical Physics of Biological Systems II (joint session BP/DY)

DY 52.3: Talk

Friday, March 31, 2023, 10:00–10:15, BAR Schö

Dynamics of vesicle clusters studied by passive x-ray microrheology — •Titus Czajka¹, Charlotte Neuhaus¹, Jette Alfken¹, Moritz Stammer¹, Yuriy Chushkin², Diego Pontoni², Christian Hoffmann³, Dragomir Milovanovic³, and Tim Salditt¹ — ¹Institut for X-ray Physics, Georg-August-Universität Göttingen, Germany — ²ESRF, Grenoble, France — ³Laboratory of Molecular Neuroscience, DZNE, Berlin, Germany

Inferring the viscoelastic properties of a complex fluid from the dynamics of suspended tracer particles is a common method to perform rheological measurements where a direct measurement of the constituents of the system is not possible or impractical. The previously observed pool formation of vesicles induced by divalent salts or the protein synapsin I is a case in point. One would like to know how the mobility of a single (tracer) particle changes in a dense pool as compared to a homogeneous vesicle suspension. Here we used x-ray correlation spectroscopy (XPCS) to measure silica nanoparticles immersed in a complex biomolecular fluid composed of small unilamellar vesicles and CaCl₂, or SUVs and Synapsin-Ia protein, both in buffer solution. While the former system leads to irregular clusters, the latter has been observed to form protein induced vesicle pools, suggesting a liquid-liquid phase separation. Analysis of the photon correlation functions reveals the presence of different timescales, which we attribute to the free diffusive motion of the tracer particles and the motion of the tracer particles that interact with the cluster.