Berlin 2012 – scientific programme

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BP: Fachverband Biologische Physik

BP 32: Physics of Cells III

BP 32.6: Talk

Friday, March 30, 2012, 10:45–11:00, H 1028

Towards the understanding of bond organization in adhesion domains: Coexistence of the dilute and the dense packing — •Daniel Schmidt¹, Timo Bihr¹, Udo Seifert¹, and Ana-Sunčana Smith² — ¹II. Institut für Theoretische Physik, Universität Stuttgart — ²Institut für Theoretische Physik and Excellence Cluster: Engineering of Advanced Materials, Universität Erlangen-Nürnberg

We study the optimal arrangement of ligand-receptor bonds in micro-domains that form during the adhesion of biological membranes. In our model-domains, the bonds are placed on a regular lattice and described by harmonic springs. The membrane also interacts with the substrate by a nonspecific potential. Additionally, we explicitly consider the effects of fluctuations of both the membrane and the bonds as well as the membrane tension. The stability of domains emerges from the analysis of the appropriate free energy density. We determine the phase diagram of the system as a function of key parameters such as the stiffness of the bonds, the ligand-receptor binding affinity, and the distance between the bonds.

In a parameter range typical for experiments, we find the commonly observed densely packed domains and a regime in which the bonds are sparsely distributed. The two regimes are separated by an energy barrier, which may signify unstable specific adhesion at intermediate densities, if one of the binding partners is immobile. If both ligands and receptors can freely diffuse through the opposing membranes, we predict a coexistence between the two domain types, which agrees with recent experimental observations.