REDUCTION OF FERRITIN IRON ON PLATINUM-ELECTRODE BY USE OF THIN-LAYERSPECTROELECTROCHEMISTRY

Thin layer spectroelectrochemistry is used to study the Fe(III) reduct ion in the shell of the ferritin. Comparison between electrochemistry measurements performed on ferritin - oxidoreduction mediator (flavin m ononucleotide) 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) re ductible depend on the apparent standard potential of the mediator sys tem. A spectrocoulometric analysis leads to a separated electron balan ce for Fe(III) and FMN reductions. Moreover a comparison with electroc hemistry of Fe(III) salts and FMN mixtures shows that Fe (III) is chel ated by FMN whereas Fe(II) is chelated by the semiquinonic flavinic in termediate. A thermodynamic calculation is used to confirm the role pl ayed by the mediator and the iron(II) ligand.