Figure 5.

Calculation of the free energy and the heat capacities for membranes that are constrained to be flat or curved with a radius of curvature of r = 60 nm (from a Monte Carlo simulation, using Eqs. 1 and 2). The free energy of the curved state is given in red, that of the flat state in blue. The lower free energy state is shown as solid lines, the higher energy states as dotted lines. The interaction with the solvent is taken to be different for the two states. This difference, ΔG_solv, differs between a–c, leading to a relative shift in the vertical direction between the free energy profiles of the flat and the curved states. (a) Flat membrane with one narrow heat capacity peak. (b) Coexistence of flat and curved membranes, leading to a structural transition at the intersection points of the free energy curves. (c) Curved membrane with a broad heat capacity peak.