Instabilities due to charge-density-curvature coupling in charged membranes.

Instabilities are caused by the reduction in the electrostatic energy when the membrane is curved with the higher charge density on the bilayer which is stretched by the curvature. In a bilayer where the charges can flip from one lipid layer to the other, there is a thermodynamic instability to a spontaneously curved state with different charge densities on the two sides. If the charges are not permitted to flip, there is a dynamical instability due to the correlated modulation of the charge density and curvature fields. Numerical estimates show that these effects are present in parameter regimes relevant to biological systems.