Coarsening Dynamics of Domains in Lipid Membranes

Abstract

We investigate diffusion and growth of liquid domains within membranes of giant unilamellar vesicles (GUVs) composed of ternary lipid mixtures. Domains appear after a temperature quench, when the membrane is cooled through a miscibility phase transition such that coexisting liquid phases form. In membranes quenched far from a miscibility critical point, circular domains nucleate and then progress within seconds to “late stage” coarsening in which domains grow via two mechanisms: (1) collision and coalescence of liquid domains, and (2) Ostwald ripening. Both mechanisms are expected to yield the same growth exponent, alpha = 1/3, where domain radius grows as time raised to a power of alpha. In membranes close to a miscibility critical point, the two liquid phases in the membrane are bi-continuous. A quench near the critical composition results in rapid changes in morphology of elongated domains; theory and simulation predict alpha = 1/2. Here we measure growth exponents for micron-scale domains in vesicles with diameters between 80 microns and 250 microns. The vesicles undergo a fast temperature quench and then are observed at roughly constant temperature. We find an exponent of alpha = 0.28±0.05 far from the critical point and alpha = 0.50±0.16 close to the critical point, in good agreement with theory.