Figure 3.

(А) Dependence of pore energy on the hydrophobic belt height, 2L, for the reference model lipid at different pore radii (specified near each curve in nanometers). The elastic parameters of the reference lipid are as follows: B _m = 8 k _B T, h _m = 2 nm, K _A ^m = 100 mN/m. The dependencies W(L) have minima, marked by color circles. For the radius r ∼ 0.675 nm (dark blue curve), pore energy W(L) has two minima with identical energies — at 2L = 0 and at 2L = 2.5 nm. (B) Schematic illustration of configurations, corresponding to two energy minima of the dark blue curve of the panel A: hydrophobic defect (2L = 2.5 nm, the hydrophobic belt surface is shown in red) and hydrophilic pore (2L = 0) of the same radius (r ∼ 0.675 nm). The states have equal energy, but substantially different cross-section of the pore lumen. The states are separated by low energy barrier of ΔW ∼ 2 k _B T, which implies high frequency of transitions between them. (C) Dependence of the optimal height of hydrophobic belt, 2L _optimal, on the pore radius. L _optimal is obtained from positions of minima of the dependencies W(L), presented on the panel A and marked by color circles. (D) Dependence of optimal pore energy on the radius r for the reference model lipid. The optimal pore energy is the energy at the minima of the dependencies W(L), presented on the panel A and marked by color circles. The local minimum of the dependence W(r) at r ₀ ≈ 1.9 nm corresponds to a metastable state of the system.