NMR kinetic studies of the ionophore X-537A-mediated transport of manganous ions across phospholipid bilayers.
Nuclear magnetic resonance spectroscopy has been applied as a method for studying manganous ions transport across the membrane of phosphatidylcholine vesicles. The rates of the ionophore X-537A (lasalocid A)-mediated Mn2+ transport have been measured as a function of ionophore concentration, pH of the vesicle suspension, and temperature. The translocation was found to occur via a neutral complex composed of one manganous ion bound in two ionized X-537A molecules (Mn X2). The activation energy for the overall transport process was determined to be 22 +/- 5 kcal/mol. Also a pKa of 5.0 +/- 0.2 was determined for the ionophore acid dissociation equilibrium in the vesicle suspension.
D000900:Anti-Bacterial Agents; D055598:Chemical Phenomena; D002621:Chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007832:Lasalocid; D008081:Liposomes; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese; D009994:Osmolar Concentration; D010713:Phosphatidylcholines; D013816:Thermodynamics
D000900:Anti-Bacterial Agents; D008081:Liposomes; D010713:Phosphatidylcholines; D008345:Manganese; D007832:Lasalocid