Manganese + 2 exhibits dynamic binding to multiple ligands in human plasma.

Plasma from fasted adult male subjects was labeled in vitro with 54MnCl2 and then fractionated using several techniques. Molecular sieve chromatography showed that the major 54Mn-containing peak had a very low molecular weight (VLMW), although four other significant peaks, one of which corresponded to the mass of transferrin (Tf), were also observed. The 54Mn content of the Tf peak increased with increasing incubation time in vitro, suggesting the oxidation of Mn+2 to Mn+3 before its association with Tf. This time-dependent effect was verified using affinity chromatography consisting of immobilized anti-Tf. Electrophoretic analyses of plasma yielded equivocal results, indicating a limited value of this method for investigating plasma manganese localization. The above findings are discussed in the context of factors that influence the oxidation and metabolism of Mn2+ in human plasma.