DEFORMATION OF GIANT LIPID BILAYER VESICLES IN SHEAR-FLOW

We describe experimental studies of the deformation of giant lipid bil ayer vesicles in shear flow. The experiments are carried out with a co unterrotating Couette apparatus. The deformation depends on the mechan ical properties of the lipid bilayer, the vesicle radius, and the visc osity of the surrounding Newtonian liquid. We show that the relevant m echanical parameter is the bending rigidity. A simple model has been d eveloped that describes the deformation of a vesicle. This model takes thermal undulations of the bilayer into account. We have obtained a v alue for the bending rigidity of dimyristoyl-phosphatidylcholine bilay ers and its value has been compared with literature data and with resu lts from micropipette aspiration experiments. From the measurements we are able to discriminate between unilamellar and multilamellar vesicl es.