Cation nuclear magnetic resonance (NMR). 7Li- and 23Na-NMR results obtained with human erythrocytes.
A short discussion of practical results and theoretical aspects of nuclear magnetic resonance (NMR) on intracellular monovalent cations is presented. 7Li- and 23Na-NMR relaxation studies on human erythrocytes are described which indicate that lithium and sodium ions are essentially free inside the cell. However, there is a contribution to transverse relaxation originating from cations diffusing through electric field gradients imposed by the cytoskeleton, which is reflected in the NMR line shape. 39K-NMR results obtained by other authors for intracellular potassium are compared with the 7Li- and 23Na-NMR results presented here. The few 39K-NMR results obtained so far do not suggest that significant differences in dynamic behavior exist between intracellular potassium and sodium. 39K-NMR studies will, in the future, certainly enhance our understanding of the intracellular state of potassium ions.