Non-ribosomally synthesized porters. These substances, like non-ribosomally synthesized channels, may be depsipeptides or non-peptide-like substances. They complex a cation in their hydrophilic interior and facilitate translocation of the complex across the membrane, exposing their hydrophobic exterior, by moving from one side of the bilayer to the other. If the free porter can cross the membrane in the uncomplexed form, the transport process can be electrophoretic, but if only the complex crosses the membrane, transport is electroneutral. Advances in the de novo design of artificial transporters and channels have been reviewed (Zhou and Lu 2022). Controlling the mobility of artificial transport systems enables precise control over activity (Bickerton and Langton 2022). Synthetic peptide scaffolds as ion channels and molecular carriers have been reviewed (Pérez-Pérez et al. 2025). Thornell et al. 2025 considered the different transepithelial voltages and the resultant movement of Cl- during short circuit and physiological open-circuit conditions. The behavior under short-circuit conditions cannot be directly extrapolated to infer behavior under physiologic conditions (Thornell et al. 2025).