Measurement of Late Stage Coarsening on Lipid Membranes

Abstract

We investigate the diffusion and growth of liquid domains in the membrane of giant unilamellar vesicles (GUVs) composed of a ternary mixture of saturated phospholipids, unsaturated phospholipids, and cholesterol when the temperature is quenched below the miscibility transition temperature. After a period of nucleation (Lifshitz, et al., 2002), domains can grow by two mechanisms in the late stages of coarsening. These mechanisms are collision and coalescence of liquid domains and Ostwald ripening. Both contribute to the measured growth exponent, z, where domain radius, R α tz. If the area fraction of one of the phases is small, the later stage of domain growth has been predicted by simulation and theory to be z = 1/3 (Laradji & Sunil Kumar, 2004). When the area fraction is increased to 50% of the surface of the membrane, simulation predicts R α t1/2 (Fan et al., 2010; Laradji & Sunil Kumar, 2005). Here we compare physical measurement of the growth exponent to theory in both cases. We also show preliminary evidence of Ostwald ripening on GUVs. Fan, J., Han, T., & Haataja, M. (2010). Submitted to J. Chem. Phys. Laradji, M., & Sunil Kumar, P. (2005). J. Chem. Phys., 123, 224902. Laradji, M., & Sunil Kumar, P. (2004). Phys. Rev. Lett., 93 (19), 198105. Lifshitz, Y., Kohler, T., Frauenheim, T., Guzmann, I., Hoffman, A., Zhang, R., Zhou, X.T., & Lee, S.T. (2002). Science, 297, 1531.