Enhancement of Na+ Diffusion in a Bicontinuous Cubic Phase by the Ionophore Monensin
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Pulsed field gradient spin-echo NMR diffusion and relaxation measurements were used to investigate howtheNa+ ionophore monensin affected the dynamics of sodium ions in a Myverol 18-99/saline bicontinuous Ia3d cubic phase (BCP). The monensin-Na+ binding number was estimated from 23Na line widths to be between 3 and 6. The dependence of the apparentNa+ diffusion coefficient on the concentration of monensin revealed monensin-induced Na+ transport. At high monensin concentrations, the enhancement of D(Na+) was offset by Na+-monensin binding. The greatest enhancement was measured at short diffusion times (del <= 5 ms), which we explain in terms of the bicontinuous topology of the cubic phase and a combination of tortuosity and bilayer permeability effects. We also propose numerical simulations which would enable the separation of the two effects. To our knowledge, this is the first study of ionophore-mediated cation diffusion in a bicontinuous cubic phase. The approach could be used to study the dynamics of hydrophilic species in the aqueous channels of BCPs and similar structures, as well as to measure the ion-transporting efficiency of ionophores.
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|Item Type:||Journal Article|
|Additional Information:||This article is freely available from the American Chemical Society website 12 months after the publication date. See links to publisher website in this record.|
|Keywords:||bicontinuous cubic phases, monoolein, ionophore, mediated transport of sodium ion, nuclear magnetic resonance, diffusion, relaxation|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)|
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology|
|Copyright Owner:||Copyright 2004 American Chemical Society|
|Deposited On:||15 Sep 2006|
|Last Modified:||29 Feb 2012 23:20|
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