Max Planck Institute for Dynamics and Self-Organization -- Department for Nonlinear Dynamics and Network Dynamics Group
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Tuesday, 11.02.2014 17 c.t.

Criticality in the Plasma Membrane of Living Cells

by Dr. Benjamin Machta
from The Lewis-Sigler Institute, Princeton University, USA

Contact person: Ahmed El Hady


MPI DS seminar room (0.77/0.79)


The plasma membrane is a two dimensional liquid composed of a diverse soup of lipids and embedded proteins. In addition to separating inside from outside, the plasma membrane contains much of the cell’s machinery for receiving and processing information. Recent experiments suggest that these membranes are tuned very close to a liquid-liquid miscibility critical point in the 2D Ising universality class. I will first review the evidence for this critical point, explain what it means and why it is surprising, and argue that it likely underlies much of the lateral heterogeneity seen in the membranes of intact cells. I will then discuss criticality’s implications for processes mediated by membrane bound proteins. Composition fluctuations mediate a critical Casimir force that acts between proteins, becoming long-ranged close to the critical point. These forces may indirectly regulate protein function by affecting their localization. In addition, a protein’s functional state could directly couple to the local membrane composition. Such a protein would be allosterically regulated by membrane perturbations that change the critical temperature or the area fractions of the two liquid phases. Finally I will present evidence showing that general anesthetics take the membrane away from this critical point at biologically relevant concentrations. I will argue that the affects of anesthetics on critical properties of the membrane could be sufficient to explain the observed changes in ion-channel function as well as the organism level anesthetic response. I will discuss ongoing experiments that seek to clarify the role of criticality in mediating the protein and organismal level changes brought about by anesthetics.

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