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BP: Fachverband Biologische Physik

BP 16: Biological Membranes I

BP 16.5: Talk

Tuesday, March 15, 2011, 11:45–12:00, ZEU 260

Structure Formation in Membranes with Quenched Protein Obstacles — •Timo Fischer and Richard Vink — Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

There is growing consensus that membrane lateral structure is heterogeneous, and characterized by micro-domains of different size and compositions. From equilibrium thermodynamics, the formation of micro-domains could be explained by critical fluctuations near a critical point of a demixing transition. Away from the critical point, one would either have a homogeneous mixture or a macroscopic demixing of the membrane components. Such a phase transition is indeed seen in model membranes, and was shown to belong to the Ising universality class. In the membranes of living cells, however, no macroscopic demixing is seen.

Using Monte-Carlo simulations of a simple model of a two-component membrane we investigate how randomly-distributed static obstacles, such as trans-membrane proteins coupling to the inner structure of the cell, influence the fate of the demixing transition. Our findings are compatible with a change in universality from Ising to random-field Ising (RFIM) [1]. This change in universality class elegantly accounts for the non-observation of macroscopic demixing in living cells, since the RFIM does not phase separate in two dimensions. Instead, we find equilibrium micro-structures, which suit well to the expected heterogeneous structure of the membrane.

[1] T. Fischer, RLC Vink, arXiv:1011.0538v1