Rigaud JL, Gary-Bobo CM. Cation diffusion selectivity in a pore model. The phosphatidylcholine/water lamellar phase.
BIOCHIMICA ET BIOPHYSICA ACTA 1977;
469:246-56. [PMID:
901786 DOI:
10.1016/0005-2736(77)90160-2]
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Abstract
The diffusion coefficients D (cm2/s), of four monovalent cations K+, Na+, Rb+ and Cs+ and of Ca2+ have been measured in phosphatidylcholine/water lamellar phase as a function of phase hydration and temperature and in the presence of divalent cations. Diffusion rates vary strongly with phase hydration, between 10(-7) and 10(-6) cm2/s for monovalent and 10(-8) and 10(-7) for Ca2+. The activation energies obtained are relatively small (5--10 kcal/mol). As the phase water content increases, a series of diffusion sequences is obtained, corresponding to the sequences predicted by Eisenman's theory of alkali ion equilibrium selectivity. This diffusional selectivity, which depends exclusively upon non-equilibrium parameters (mobility) within the hydrophilic path is discussed in respect to current theories of pore selectivity.
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