Berlin 2012 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 18: Posters: Statistical Physics in Biological Systems

BP 18.8: Poster

Mittwoch, 28. März 2012, 17:30–19:30, Poster A

Nucleation of ligand-receptor-domains in membrane adhesion — •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 investigate the nucleation of adhesion domains consisting of ligand-receptor bonds forming between membranes that also interact by a nonspecific potential. We first determine the critical size of the nucleus within the capillary approximation. The time evolution of the nucleation process is considered to take place in a number of rate-dependent coupled stochastic events, each denoting the association or dissociation of a bond. The effective rates for each of these events are calculated by taking into account the membrane deformation and fluctuations. Based on these rates, we construct a discrete master equation from which the characteristic nucleation time is obtained numerically or as an analytic estimate. We validate our model by performing extensive Langevin simulations of an adherent fluctuating membrane, including the ligand-receptor unbinding. We find excellent agreement between the different approaches, particularly in the regime of strong intra-bond correlations.

We show that for experimentally relevant parameters a stable nuclei consists typically of only a few bonds. Furthermore, we find a strong dependence of the characteristic nucleation time on the distance between the receptors which could explain some of the recurrent threshold length-scales in cell adhesion assays.