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Single-file transport of water through membrane channels

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Abstract

Water at interfaces governs many processes on the molecular scale from electrochemical and enzymatic reactions to protein folding. Here we focus on water transport through proteinaceous pores that are so narrow that the water molecules cannot overtake each other in the pore. After a short introduction into the single-file transport theory, we analyze experiments in which the unitary water permeability, pf, of water channel proteins (aquaporins, AQPs), potassium channels (KcsA), and antibiotics (gramicidin-A derivatives) has been obtained. A short outline of the underlying methods (scanning electrochemical microscopy, fluorescence correlation spectroscopy, measurements of vesicle light scattering) is also provided. We conclude that pf increases exponentially with a decreasing number NH of hydrogen bond donating or accepting residues in the channel wall. The variance in NH is responsible for a more than hundredfold change in pf. The dehydration penalty at the channel mouth has a smaller effect on pf. The intricate link between pf and the Gibbs activation energy barrier, ΔGt, for water flow suggests that conformational transitions of water channels act as a third determinant of pf.

Graphical abstract: Single-file transport of water through membrane channels

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Publication details

The article was received on 13 Jun 2018, accepted on 18 Jun 2018 and first published on 18 Jun 2018


Article type: Paper
DOI: 10.1039/C8FD00122G
Citation: Faraday Discuss., 2018, Advance Article
  • Open access: Creative Commons BY license
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    Single-file transport of water through membrane channels

    A. Horner and P. Pohl, Faraday Discuss., 2018, Advance Article , DOI: 10.1039/C8FD00122G

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