Figure 1.

Ising criticality in the plasma membrane. (A) The model presented here assumes that cell plasma membranes are tuned to the proximity of a 2D Ising critical point with a miscibility phase boundary given by the thick black line. Contours show regions of constant correlation length. Their shapes are identical for any system in the 2D Ising universality class, except for the slope of the rectilinear diameter (long-dashed green line's tilt; see the Supporting Material), which describes how the fraction of phases changes with temperature. Experiments in GPMVs give a critical temperature of ∼22°C and calibrate the contours (15). Most simulations are conducted at the red point, which is hypothesized to represent physiological conditions. (B) Below the critical temperature, intact plasma membranes on living cells appear uniform at optical length scales (red arrows), whereas attached plasma membrane vesicles are macroscopically phase-separated (blue arrowheads point to phase boundaries). Detailed methods for A and B are provided in the Supporting Material. (Color online.)