Uptake and release of iron by ferritin adsorbed at tin-doped indium oxide electrodes

In this work, the uptake and release of iron by ferritin using direct elect rochemical techniques have been investigated for the first time. Adsorption of ferritin from phosphate solution onto tin-doped indium oxide (ITO) at o pen circuit potential gives about one monolayer of ferritin. The ferritin l ayer is electroactive and therefore lends itself to electrochemical analysi s; cyclic voltammetry was the principal method used in this study. In the p resence of EDTA, iron is not removed at open circuit potential. However, wh en the ITO/ferritin electrode is subjected to -0.70 V, the anodic branch is no longer present in the current-potential curve, indicating that the redu ction of core iron had induced the removal of iron from the protein shell. Adsorbed ferritin, emptied in this fashion, was exposed to ferrous ion at 0 .20 V. The ensuing current-potential curve showed the original peak pattern , suggesting that iron had been reincorporated into the apoferritin shell. An authentic sample of adsorbed apoferritin exposed to ferrous ion, exhibit ed the same current-potential response as electrochemically emptied ferriti n, supporting the conclusion that apoferritin results from the reduction of ITO/ferritin in the presence of an iron chelator. These studies show that ferritin adsorbed at an ITO electrode is a promising venue to study not onl y ferritin's electrochemistry but also its functions.