Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 48: Colloids and Complex Liquids III

CPP 48.2: Talk

Friday, March 26, 2010, 10:45–11:00, H39

On the diffusion of circular domains on a spherical vesicle — •Saeedeh Aliaskarisohi and Thomas.M Fischer — Institut fuer Experimentalphysik, Universitaet Bayreuth, 95440 Bayreuth, Germany

Tracking the motion of lipid domains on a vesicle is a rheological technique allowing the measurement of surface shear viscosities of vesicular lipid phases. The ratio of surface to bulk viscosity defines a viscous length scale. Hydrodynamic interactions split the motion of the domains into different modes of diffusion. The measurability of surface shear viscosities from any mode of diffusion is limited to viscous length scales between the radius of the domains and the radius of the vesicle. Switching between the various modes of diffusion is a trade between sensitivity gained and resolution lost by the hydrodynamic interactions leaving the measurability unchanged. Measurability drops with the number of domains making single-domain rheology the best technique to measure surface shear viscosities. Ultimately confinement of the domains to small vesicles renders measurements of surface rheological properties with domain tracking rheology impossible. Experiments on domains in vesicles of a mixture of dioleoyl phosphatidylcholine (DOPC),dipalmytoylphosphatidylcholin(DPPC),and cholesterol(Chol) exhibit diffusion that is entirely controlled by dissipation into the water. The diffusion is suppresed compared to the diffusion of isolated domains in a flat membrane due to confinement to the curved vesicle and by hydrodynamic interactions between the domains. Effects of surface shear viscosity can be neglected.