Trajectory proportions estimates per channel exhibiting a connected path between opposite aqueous media involving side chains heavy atoms in CS-I residues (blue), CS-I and Y23 (cyan, AQP0 only), or CS-I plus CS-II residues with and without Y23 (magenta, AQP0 only). Proportion estimates for water-only single-files, which may include interactions with pore-exposed backbone polar atoms, are shown in green. Connected paths in AQP0 involving CS-II residues only (or equivalent positions in AQP1) or paths involving F24 in AQP1 (equivalent to Y23 in AQP0) had proportion estimates with magnitude comparable to the estimated errors and were not included in the plot.