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

Facilitated water permeation through narrow biological channels is fundamental for all forms of life. 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. This is a first step in understanding the energetic contributions in various biological and artificial channels exhibiting vastly different pore geometries.

促进水分通过狭窄的生物通道渗透是所有生命形式的基本特征。此过程涉及大量水分进入单列区域并与其通道衬里的氨基酸残基形成氢键。尽管水分渗透在健康与疾病以及生物技术应用中具有重要意义，但其能量学特性仍难以捉摸。虽然通过温度依赖性水分渗透率测量可以轻易获得吉布斯自由能的焓变贡献，但熵变贡献的估算则需要水分渗透速率的温度依赖性信息。通过精确测量水分通过AQP1的水分渗透的活化能，并确定精确的单通道渗透率，我们首次能够估算出通过狭窄生物通道的水分渗透的熵垒。这是理解在具有截然不同孔道几何形状的各种生物和人工通道中能量贡献的第一步。