Entropic barrier of water permeation through single-file channels

Authors:

Johann Wachlmayr, Gotthold Fläschner, Kristyna Pluhackova, Walter Sandtner, Christine Siligan & Andreas Horner
 
DOI: https://doi.org/10.1021/acscatal.3c01505
 
Instrument(s) Used: SFM-2000/3000/4000, µSFM, MOS-200
 

Abstract

Facilitated water permeation through narrow biological channels is fundamental for all forms of life. Despite its significance in health and disease as well as for biotechnological applications, the energetics of water permeation are still elusive. Gibbs free energy of activation is composed of an enthalpic and an entropic component. Whereas the enthalpic contribution 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. Here, we estimate, by means of accurate activation energy measurements of water permeation through Aquaporin-1 and by determining the accurate single channel permeability, the entropic barrier of water permeation through a narrow biological channel. Thereby the calculated value for $\triangle {S}^{{{\ddagger}} }$ = 2.01 ± 0.82 J/(mol·K) links the activation energy of 3.75 ± 0.16 kcal/mol with its efficient water conduction rate of ~1010 water molecules/second. This is a first step in understanding the energetic contributions in various biological and artificial channels exhibiting vastly different pore geometries.