Regensburg 2022 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 17: Membranes and Vesicles

BP 17.1: Vortrag

Mittwoch, 7. September 2022, 15:00–15:15, H13

Lipid domain diffusion in confined geometry — •Claudia Steinem, Nikolas K. Teiwes, and Ole M. Schütte — Georg-August Universität, Göttingen, Germany

Pore-spanning membranes (PSMs) are well-suited to investigate lipid domain diffusion. Recent findings have highlighted the dynamic nature of such lipid domains in the plasma membrane of mammalian cells and the key role of the underlying cytoskeleton network in confining their diffusion. We established PSMs composed of DOPC, sphingomyelin, and cholesterol with co-existing liquid ordered (lo)/liquid disordered (ld) domains on silicon substrates with micrometer-sized pores to investigate the diffusion of lo-domains confined in the freestanding parts of the PSMs. We compared the lo-domains in the artificial PSMs with PSMs derived from spreading giant plasma membrane vesicles (GPMVs) obtained from HEK-293 cells. In both cases, mobile ordered domains are visualized by fluorescence microscopy. From the trajectories of the individual mobile domains, the MSD is determined, which provides the diffusion constants as a function of domain size. The analysis reveals that the domains' diffusion constants are slowed down by orders of magnitude due to the confinement in the PSM, where the drag force is governed by both the friction in the bilayer and the coupling to the aqueous phase compared to the unrestricted case. From the analysis, the membrane surface viscosity can be extracted, which is by a factor of four smaller in case of the naturally derived membranes compared to the artificial ones, which can be explained in terms of the large protein content in the GPMV-derived membranes.