1H NMR study of valinomycin conformation in a phospholipid bilayer.

Our understanding of how ions pass across biological membranes has been greatly advanced by the study of small molecules which are capable of enhancing ion transport. The concepts of ion movement through channels or via mobile ion carriers have arisen from studies of model systems. However, direct probing at the molecular level of the process of ion movement in a membrane system has proved difficult. The electrical properties of black lipid membrane model systems do not provide information about the details of ionophore location or conformation. Spectroscopic methods which are suited for probing the details of ionophore conformation and the stoichometry of ion binding have been confined largely to organic solvent systems which are limited as models for biological membranes. We report here proton magnetic resonance (1H NMR) spectroscopic studies which investigate valinomycin conformation and ion binding in small bilayer vesicles.