Domains in biological membranes are often highly dynamic. Intriguing examples are the patterns formed during T-cell adhesion. The patterns are composed of domains that contain either short or long receptor-ligand complexes, and exhibit a characteristic time-dependent evolution. In my talk, I will discuss several mechanisms that lead to the formation of protein domains during membrane adhesion. The domain formation can be driven either by membrane fluctuations, or by a length mismatch of receptor-ligand complexes as in the case of the T-cell patterns. In our models, the membranes are described as discretized elastic sheets, and the receptors and ligands are captured as single molecules. The attraction between receptors and ligands in apposing membranes is modeled via an interaction potential that depends on the local membrane separation. The calculation of equilibrium properties is greatly simplified by integrating over all possible distributions of receptors and ligands in the partition function of our model. This integration leads to an effective adhesion potential of the membranes. Dynamic Monte Carlo simulations show domain evolutions with a striking similarity to the T-cell patterns. In addition, the simulations provide insights on the role of self-assembly mechanisms and active cytoskeletal processes in cell adhesion.

References:
(1) Weikl, T. R. & Lipowsky, R. (2006). Membrane adhesion and domain formation. In: Leitmannova Liu, A. (ed.), Advances in Planar Lipid Bilayers and Liposomes, Vol. 5, pp. 63-127, Elsevier, Amsterdam.
(2) Asfaw, M., Rozycki, B., Lipowsky, R., & Weikl, T. R. (2006). Membrane adhesion via competing receptor/ligand bonds. Europhys. Lett. 76, 703-709.
(3) Rozycki, B., Lipowsky, R., & Weikl, T. R. (2006). Adhesion of membranes with active stickers. Phys. Rev. Lett. 96, 048101.
(4) Weikl, T. R, & Lipowsky, R. (2004). Pattern formation during T-cell adhesion. Biophys. J. 87, 3665-3678.