Theory 25/Solvation & interfaces/Membrane permeability
Permeability Is Solute Against Pore
The claim
Membrane water permeability is set by the ratio of solute size to pore radius, so a pore that passes water can still exclude small ions.
01Mechanism
Passage requires the solute to fit and to shed its hydration shell; the ratio determines the energy cost.
02Prediction
Selectivity should track the size ratio.
03Refutation
Selectivity tracking pore chemistry alone would remove size.