Interaction of Mn++ with submitochondrial particles

The aerobic uptake of Mn++ in rat liver mitochondria gives rise to an internal ESR signal which is the sum of two components: a sextet signal corresponding to hydrated Mn++ and a single line representing the spin exchange signal. While no problems arise from the interpretation of the sextet signal, the spin exchange component has been attributed either to Mn++ binding to specific energy-dependent membrane sites or to Mn3(PO4)2 precipitate. The aim of the present paper is to study the interaction between Mn++ and the 'internal' mitochondrial membrane surface without interference due to phosphate presence (and to external Mn-EDTA complex signal), accepting that submitochondrial particles are 'inside-out' membranes in which the internal mitochondrial membrane surface is in contact with the external medium