Open AccessNet proton-hydroxyl permeability of large unilamellar liposomes measured by an acid-base titration technique.
Author(s) -
J. Wylie Nichols,
David Deamer
Publication year - 1980
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.77.4.2038
Subject(s) - titration , chemistry , bilayer , permeability (electromagnetism) , liposome , proton , acid–base titration , lipid bilayer , hydrogen bond , membrane , ion , titration curve , molecule , proton transport , inorganic chemistry , organic chemistry , biochemistry , physics , quantum mechanics
The net proton-hydroxyl permeability of large unilamellar liposomes has been measured by an acid-base pulse titration technique and has been determined to be several orders of magnitude greater than that measured for other monovalent ions. This permeability is relatively insensitive to variations in lipid composition. Proton permeability and hydroxyl permeability vary with pH 6 to 8, and this variation can occur in the absence of alterations in surface charge density resulting from titrations of acidic and basic groups on the lipids. In order to account for the exceptionally high proton-hydroxyl permeability with respect to other monovalent ions, we propose that protons or hydroxyls or both interact with clusters of hydrogen-bonded water molecules in the lipid bilayer, such that they are transferred across the bilayer by rearrangement of hydrogen bonds in a manner similar to their transport in water and ice.