Coarsening dynamics of domains in lipid membranes

Abstract

We investigate isothermal diffusion and growth of micron-scale liquid domains within membranes of free-floating giant unilamellar vesicles (GUVs) with diameters between 80µm and 250µm. Domains appear after a rapid 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<super>&alpha</super>. We measure &alpha = 0.28 ± 0.05, in excellent agreement. 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. In this case, we measure &alpha = 0.50 ± 0.16, consistent with theory and simulation.