REDUCTION OF FERRITIN IRON ON PLATINUM-ELECTRODE BY USE OF THIN-LAYER SPECTROELECTROCHEMISTRY

Thin layer spectroelectrochemistry is used to study the Fe(III) reduction in the shell of the ferritin. Comparison between electrochemistry measurements performed on ferritin - oxidoreduction mediator (flavin mononucleotide) mixtures with and without 2.2'-bipyridine shows that a mediator is necessary in order to perform Fe(III) reduction. The rate of release of Fe(II) from the shell and the total number of Fe(III) reductible depend on the apparent standard potential of the mediator system. A spectrocoulometric analysis leads to a separated electron balance for Fe(III) and FMN reductions. Moreover a comparison with electrochemistry of Fe(III) salts and FMN mixtures shows that Fe (III) is chelated by FMN whereas Fe(II) is chelated by the semiquinonic flavinic intermediate. A thermodynamic calculation is used to confirm the role played by the mediator and the iron(II) ligand.