Figure 2.

Accessible volume estimation. (a) The panel report a cut of the 3D averaged occupancy map ${\tilde{M}}_{\mathrm{x},\mathrm{y},\mathrm{z}}$ for the empty pore. Blue areas corresponds to region that are fully accessible by the electrolyte ${\tilde{M}}_{\mathrm{x},\mathrm{y},\mathrm{z}}=1$ while white ones do not contribute to the volume useful for the ions transport between the two side of the membrane, ${\tilde{M}}_{\mathrm{x},\mathrm{y},\mathrm{z}}=0$. (b) Inverse of the accessible area, A_z, along the pore. The empty pore profile is plotted as dashed black line. The two peaks at $z\simeq 50$ Å and $\simeq 20$ Å correspond to the central αHL constriction and to the constriction close to the barrel entrance, respectively. The five solid lines refer to the five Ala replicas. (c) Slices of ${\tilde{M}}_{\mathrm{x},\mathrm{y},\mathrm{z}}$ normal to the pore z-axis passing through the two constrictions (z = 19 Å and z = 48 Å) and the vestibule (z = 70 Å) for the four homopeptides.