Liposomes, Ionophores, Peptide drugs, Ions-Migration and velocity, Extrusion process, Nuclear magnetic resonance, Bilayer lipid membranes, Membranes (Biology), Monesin, Valinomycin, Ion transport, О_О_Na-NMR, О_ЉЃ_K-NMR, Extrusion, Detergent dialysis, Lipid bilayers
As antibiotic treatments of infection are becoming increasingly ineffective in modern times, it is more important than ever to investigate novel compounds for their potential to combat illness. A particular new class of molecules, termed peptide therapeutics, exhibit their antibiotic properties through binding to the plasma membrane of bacteria and subsequently disrupting membrane integrity (Oyston et al., 2009). It is necessary to develop protocols to characterize these compounds in order to determine whether or not they will be suitable for use in living systems to fight disease down the pipeline. The focus of this study was to develop methods for using ²³Na- and ³⁹K-NMR to observe ion transport across liposomal membranes, as the interruption of ion homeostasis is a significant mechanism used by antibiotic compounds to exert their effect. Ionophores are molecules synthesized by microorganisms and are known to have antibiotic properties because they transport ions down their concentration gradient. Monensin, a sodium transporter, and valinomycin, a potassium transporter, were the ionophores of choice. Of particular interest was valinomycin because it is a cyclic peptide molecule similar to many new therapeutics being investigated in other studies. Through kinetic evaluation of NMR spectra by a method outlined by Riddell and Hayer in the 1985 study, the rate laws for transport were determined. For sodium cations across liposomal membranes produced by an extrusion protocol in 200mM NaCL by monensin, the rate was equal to 4.37·10⁵ M ⁻¹s⁻¹[monensin]. The transport of potassium cations in 200 mM KCL by valinomycin across liposomal membranes prepared by a detergent dialysis method was found to have rate= rate=3.93·10⁵M⁻¹s⁻¹[valinomycin].
Loew, Colby Rachel, "²³Na- and ³⁹K-NMR studies of monensin- and valinomycin-mediated ion transport through liposomal membranes" (2013). Honors Project, Smith College, Northampton, MA.
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