Figure 7.

Hydration profile of Na⁺ crossing the TMD. (A) First hydration shell composition (calculated with a distance cutoff of 3.2 Å for all Na⁺ ligands and averaged over a time window of 0.25 ns). The colour code is the following: water (cyan), Cl⁻ (red), Na⁺ (blue) and oxygen atoms from the side chains of Ser6′ (green), Thr2′ (yellow) and Glu-2′ (orange). (B) Z-dependent hydration profile of the pulled Na⁺. In each slice of 1 Å, the water density of the ion’s first water shell was computed along the z-axis. Selected pore structures (from a to f) are represented on the bottom panel (C) for six different snapshots; the pulled ion is displayed as a yellow sphere, water molecules are shown as red and white sticks, and water molecules present in the first hydration shell are represented by larger sticks. Pore-lining residues are shown in cyan. Transparent spheres represent waters and ions present in the crystal structure: small red spheres for water and large spheres for ions (red for Br⁻ and blue for Cs⁺ and Rb⁺).