(747g) Pattern Formation and Coarsening in Molecularly-Tethered Lipid Membranes

Many biological processes involve the binding and subsequent spatial reorganization of complementary molecules on apposed membranes. Recent experiments have utilized short, laterally mobile DNA strands of various lengths to tether fluctuating and supported lipid bilayers, resulting in interesting patterns in which DNA strands of similar lengths colocalize in spatial regions on the length scale of microns [1]. We use theoretical and computational methods to study the dynamics of a fluctuating membrane that is tethered to a supported membrane by laterally mobile molecules. The shape of the fluctuating membrane is governed by a time-dependent Ginzburg-Landau model, which is coupled to reaction-diffusion equations describing the time evolution of the concentrations of molecules. The free energy of the system accounts for the surface tension and bending rigidity of the membrane, as well as molecular binding [2]. When two or more molecular species with different natural lengths are present, the species segregate into distinct spatial regions, with the local membrane separation accommodating the natural length of the molecules. Different patterns of segregation are observed depending on system parameters including the number of types of molecules, their natural lengths, and their relative concentrations. Interestingly, we find by analytical means that there is a driving force for molecular phase separation even in the limit of vanishing surface tension and bending rigidity. The model provides insight into recent experimental results, and we suggest additional experimental tests aimed at gaining additional insight into biological phenomena.

[1] Chung M.; Koo B.J.; Boxer S.G. Farad. Discuss. 2013, 161, 333-345.

[2] Qi S.Y.; Groves J.T.; Chakraborty A.K. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 6548–6553.