Iron(III) Complexation of Desferrioxamine B Encapsulated in Apoferritin

The dissociation of apoferritin into subunits at pH 2 followed by its reformation at pH 7.4 in presence of Desferrioxamine B (DFO) gives rise to a solution containing three DFO molecules trapped within the apoferritin (Apo-ferritin:DFO) and DFO molecules outside it. The untrapped DFO molecules in the solution were removed from Apo-ferritin:DFO by exhaustive dialysis until a negligible concentration was confirmed. The addition of Fe(III) to the dialyzed solution of Apo-ferritin:DFO resulted in the appearance of an orange-red color. The UV-Vis spectrum of this solution shows the characteristic absorption of the [DFOFe] complex centered at 425 nm. Following a similar procedure as for DFO, only one molecule of [DFOFe] was trapped in the apoferritin. The above results demonstrate the possibility of encapsulating a large molecule such as DFO in the apoferritin and, more interestingly, the ability of these DFO-encapsulated molecules to react with Fe(III) to give rise to an encapsulated [DFOFe] complex within the apoferritin.