Manganous Ion as a Spin Label in Studies of Mitochondrial Uptake of Manganese

Manganous ion (Mn2+) has been used as a spin label for studies of divalent cation uptake by rat liver mitochondria. Spin exchange, observed in the electron paramagnetic resonance (EPR) spectrum of a fraction of the transported Mn2+, shows that this fraction is bound in regions of high local concentration within the mitochondria. The average separation of manganese ions in that fraction is estimated to be 4.0±0.6 A at the time of greatest concentration