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BP: Fachverband Biologische Physik

BP 6: Posters: Membranes and vesicles

BP 6.10: Poster

Montag, 31. März 2014, 17:30–19:30, P3

Environmental effects on diffusion in the Trypanosome membrane — Marius Glogger, Andreas Hartel, Markus Engstler, and •Susanne Fenz — University of Würzburg, Biocenter: Zoology I, Würzburg, Germany

Trypanosomes (T. brucei) are the pathogen of sleeping sickness. They exhibit a surface coat of identical variable surface glycoproteins (VSGs) as protection against the innate immune response of the host. This coat is extremely dense, but also highly dynamic. This ambivalent character is in the focus of our research interest. Here, we will present our insights on the effect of the environmental parameters, ambient medium and lipid matrix, on VSG dynamics as measured by Fluorescence Recovery after Photobleaching (FRAP). In order to perform FRAP on endogenously highly motile trypanosomes they have to be immobilized, e.g. embedded in gelatin gels. To probe whether this condition biases the measurements we performed control experiments in model membranes. Surprisingly, neither the absolute diffusion coefficient nor the mobile fraction was affected. We hypothesize that a low viscosity layer of buffer at the trypanosome-gelatine interface served as a lubricant. Thus, it ensured that the observable diffusion was still dominated by frictional dissipation within the membrane and with neighboring variant and invariant membrane proteins. VSGs are anchored to the cell membrane via a glycosylphosphatidylinositol (GPI) moiety. In a second set of experiments we will characterize the fluidity of the lipid matrix both in the inner and outer membrane leaflet and thus define the framework for a holistic interpretation of VSG dynamics.