Direct High-resolution Nuclear Magnetic Resonance Studies of Cation Transport in Vivo Na+ Transport in Yeast Cells

A new nuclear magnetic resonance (NMR) method for monitoring transmembrane metal cation transport is reported. It is illustrated with a study of Na+ efflux from Na+-rich yeast cells. The technique involves the use of an anionic paramagnetic shift reagent, present only outside the cells, to induce a splitting of the sodium-23 NMR peak, in this case, into components representing intra- and extracellular Na+. The time course of the efflux is in good agreement with the literature and can be well fitted with a double exponential decay expression. Splitting of the lithium-7 NMR signal from a suspension of Li+-rich respiratory-deficient, petite yeasts is also reported