Regensburg 2004 – scientific programme

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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.113: Poster

Friday, March 12, 2004, 10:30–13:00, B

Vesicles in the Optical Stretcher - Shape changes induced by stress-dependent flip-flop processes — •Frank Sauer, Stefan Schinkinger, Falk Wottawah, Bryan Lincoln, and Jochen Guck — Fakultät für Physik und Geowissenschaften, Univeristät Leipzig

We have investigated giant unilamellar vesicles (DLPC and C12E4) with an optical stretcher. This laser-based micromanipulation tool induces optical surface stresses that can trap vesicles and deform them from spherical into a prolate shape. The observed deformation increased linearly with applied stresses ranging from 1-20 Pa. This deformation was reversible upon immediate removal of the stress. Surprisingly, under continued stress for more than 1s, the vesicle returned to its spherical shape with the return rate increasing with stress. When the stress was then removed, the vesicle became oblate and recovered its equilibrium spherical shape only after a very long time (10-20 min). This effect could be repeated several times with the same vesicle, excluding damage to the vesicle as possible cause. The most likely explanation of this phenomenon is a stress dependent flip-flop rate between outer and inner leaflets. This leads to a stress dependent spontaneous curvature, which changes the equilibrium shape of the vesicle. Further experiments to test this hypothesis are underway.