Dyanmics and Stability of Membrane Systems (REU Supplement)

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This project is an interrelated theoretical and experimental work on the kinetics of adhesion and fusion of cell-size vesicles, based on physical chemistry and hydrodynamics of thin films. The study focuses on the similarity between the kinetics of aggregation and coalescence of bubbles and drops in colloid systems and the kinetics of adhesion, instability, and fusion in membrane systems, where the specific mechanical and permeability properties of membranes are taken into account. The rate of mutual approach of deformable permeable membranes, the stability of films between interacting membranes, the rate of expansion of membrane contact during adhesion, and the rate of shape relaxation after membrane fusion are evaluated theoretically. From these results, the total times of vesicle adhesion and fusion are calculated as a function of the membrane tension, membrane permeability, intermembrane forces and liquid film viscosity. The times of adhesion and fusion of cell-size phospholipid vesicles, held by micropipettes, are measured as a function of the vesicle membrane tensions and the concentration of ions in the water solutions where the vesicles are placed. The theoretically calculated times of adhesion and fusion are compared with the experimentally measured values for phosphatidylcholine and phosphatidylserine vesicles.