View of Hydrogen/Hydroxide Flux Across Lipid Membranes

A topic emerging roughly 30 years ago and engendering an incompletely resolved controversy is reviewed in this article: the relatively high permeability and pH independence associated with H⁺/OH⁻ passive movements across lipid membranes. We summarize the expected characteristics of simple H⁺/OH⁻ dif...

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Bibliographic Details
Published in:The Journal of membrane biology 2010-09, Vol.237 (1), p.21-30
Main Authors: Nichols, J. Wylie, Abercrombie, R. F
Format: Article
Language:English
Subjects:
Animals
Biochemistry
Biomedical and Life Sciences
Cellular biology
Charge delocalization
Diffusion
Human Physiology
Humans
Hydrogen
Hydrogen - metabolism
Hydrogen-Ion Concentration
Hydroxides - metabolism
Ions
Life Sciences
Lipids
Membrane Lipids - metabolism
Membranes
Permeability
Proton permeation
Protons
Water cluster
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Summary:A topic emerging roughly 30 years ago and engendering an incompletely resolved controversy is reviewed in this article: the relatively high permeability and pH independence associated with H⁺/OH⁻ passive movements across lipid membranes. We summarize the expected characteristics of simple H⁺/OH⁻ diffusion and those of a reaction between H⁺ and OH⁻ being attracted from opposite surfaces and condensing in an interfacial zone of the membrane. An interfacial H⁺/OH⁻ reaction mechanism gives the experimentally observed behavior of an H⁺/OH⁻ flux that is independent of the pH measurement range. This mechanism assumes that H⁺ and OH⁻ within the interfacial zone become electrostatically aligned on opposite sides of the hydrophobic membrane core. Electrostatic attraction and charge delocalization among a small cluster of water molecules surrounding the ions reduce the Born energy for H⁺/OH⁻ insertion into lipid. This transmembrane condensation model predicts the magnitude of the experimentally determined H⁺/OH⁻ flux, which is significantly greater than that of other monovalent ions. The consequences of an elevated H⁺/OH⁻ permeability compared to other ions and the relative pH independence of this flux have consequences for understanding the chemical evolution of life.
ISSN:0022-2631
1432-1424
DOI:10.1007/s00232-010-9303-0