Manganese as a calcium probe: Electron paramagnetic resonance and nuclear magnetic resonance spectroscopy of intact cells

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Abstract
When Lettree cells are exposed to Mn2+, the cation becomes associated with cells in two ways: in a relatively loose and mobile manner that gives a six-line EPR spectrum designated Mn b *, and in an immobile, relatively tight manner that gives no detectable EPR spectrum, designated Mn b . Mn b * is probably on the surface of cells; most Mn b is probably inside cells. NMR measurements of Lettree cell suspensions show two water proton relaxation rates and confirm the existence of cell-associated Mn. Human erythrocytes, on the other hand, bind no Mn2+ under these conditions, as judged by EPR and NMR measurements. Virally-treated Lettree cells show an increase in Mn b (but not in Mn b *). They also show a third water proton relaxation rate.