Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 7: Posters I

BP 7.47: Poster

Monday, February 25, 2008, 17:00–19:30, Poster A

Translational Brownian motion and rotational shape deformations of freely suspended micron-sized phospholipid vesicles — •Christoph Herold, Eugene P. Petrov, and Petra Schwille — Biophysics / BIOTEC, TU Dresden, Tatzberg 47-51, 01307 Dresden

Do shape fluctuations of a body suspended in a viscous fluid affect its translational diffusion coefficient? Theoretical studies [1, 2] predict the effect as large as ∼ 20%. However, to the best of our knowledge, this prediction has never been challenged experimentally. We carry out video microscopy studies on freely suspended fluorescently labeled giant unilamellar vesicles (GUVs) with radii in the range of R=2−7µ m, both in the tensed state and showing pronounced shape fluctuations (|Δ R|/⟨R⟩∼ 0.1). In contrast to the predictions [1, 2], we find that vesicles, irrespectively of the presence or absence of shape fluctuations, follow the Einstein−Stokes relation within our experimental uncertainty (2% for the GUV radius and 3% for the diffusion coefficient). In addition, we study the apparent rotational diffusion of undulating vesicles. We find that the rotational diffusion of the principal axis of the gyration tensor of the vesicle image is about two orders of magnitude faster than that of a rigid spherical body and is closely related to the slowest shape relaxation rate of the vesicle.
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