Supplementary Material for 'Entropic barrier of water permeation through single-file channels'

This process involves dehydration of bulk water entering the single-file region and hydrogen bond formation with channel lining amino acid residues. Despite its significance in health and disease as well as for biotechnological applications the energetics of water permeation are still elusive.

Whereas the enthalpic contribution to Gibbs free energy is readily accessible via temperature dependent water permeability measurements, estimation of the entropic contribution requires information on the temperature dependence of the rate of water permeation. By means of accurate activation energy measurements of water permeation through AQP1 and by determining the accurate single channel permeability we were, for the first time, able to estimate the entropic barrier of water permeation through a narrow biological channel.