title: 23Na-nuclear magnetic resonance investigation of gramicidin-induced ion transport through membranes under equilibrium conditions.
abstract: A technique for investigating the gramicidin-facilitated transport of Na+ ions across lipid bilayers of large unilamellar vesicles under the condition of ionic equilibrium has been developed using a combination of heat incubation of the gramicidin with the vesicles and 23Na-nuclear magnetic resonance (NMR) spectroscopy. Isolation of the two 23Na-NMR signals from the intra- and extravesicular Na+ with the shift reagent, dysprosium (III) tripolyphosphate, allows the equilibrium flux of Na+ through the gramicidin channels to be detected and treated as a two-site exchange process. This study indicates that the transport of Na+ through gramicidin channels is second order with respect to the gramicidin concentration.
mesh_terms: D006096:Gramicidin; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D012964:Sodium
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D006096:Gramicidin; D012964:Sodium