Ion Transport Across Synthetic and Biological Membranes: Ionophore-Mediated Transport

摘要

The objectives were: to set-up a research laboratory; to initiate membrane related research; to investigate ionophoremediated transport and to involve students in research. Synthetic compounds the lariat ethers and a non-cyclic di-n-propyl diamide were investigated. These compounds were known to form complexes with cations in organic solvents however, their ionophoretic activity in model membranes has not been previously demonstrated. We were able to show that some lariat ethers mediate potassium transport across phosphatidylcholine bilayers and that the diamide induced calcium movement across lipid membranes. The polyether carboxylic acids A23187 and X537A were extensively investigated. The inital rates of calcium movement across lipid bilayers were measured as a function of the ionophore and calcium concentration. It has been found that the transported complex has a stoichiometry of ionophore:calcium 2:1 and 1:1 for A23187 and X537A respectively. However, esterification of the carboxylic group of A23187 to yield the appropriate methyl ester reduced the potency more than 200 fold and the stoichiometry was changed to ionophore:calcium 1:1.