Postprint version. Published in Proceedings of the National Academy of Sciences of the United States of America, Volume 82, Issue 11, June 1, 1985, pages 3640-3643. Copyright © 1985 National Academy of Sciences. The original publication is available at http://www.pnas.org/content/82/11/3640.abstract.
NOTE: At the time of publication, the author Richard B. Frankel was not yet affiliated with Cal Poly.
Mammalian ferritin from horse spleen undergoes an electrochemical or chemical reduction reaction in which each iron atom present is reduced by one electron (2300 electrons per ferritin molecule containing 2300 Fe3+ ions). Midpoint potentials of -190 mV, -310 mV, and -416 mV were determined at pH 7.0, 8.0, and 9.0. This variation of potential with pH indicates that ≈ 2 H+ are transferred to the core for each Fe3+ reduced to Fe2+. Mössbauer measurements of partially reduced ferritin give spectra that consist of a ferric quadrupole doublet with a superposed ferrous quadrupole doublet. The relative intensities of these doublets are consistent with the electrochemically determined degree of reduction.