Comparative Structural and Chemical Studies of Ferritin Cores with Gradual Removal of their Iron Contents

GÁLVEZ, N.; SÁNCHEZ, P.; FERNÁNDEZ, B.; CUESTA, R.; CEOLÍN, M.; CLEMENTE-LEÓN, M.; TRASOBARES, S.; LÓPEZ-HARO, M.; CALVINO, J.J.; STEPHAN, O; DOMÍNGUEZ-VERA, J.M.

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY

Año: 2008 vol. 130 p. 8062 - 8068

0002-7863

Transmission Electron Microscopy (TEM), X-ray Absorption Near Edge Spectroscopy (XANES), Electron Energy-Loss Spectroscopy (EELS), Small-Angle X-ray Scattering (SAXS), and SQUID magnetic studies were performed in a batch of horse spleen ferritins from which iron had been gradually removed, yielding samples containing 2200, 1200, 500 and 200 iron atoms. Taken together, findings obtained demonstrate that the ferritin iron core consists of a polyphasic structure (ferrihydrite, magnetite, hematite), and that the proportion of phases is modified by iron removal. Thus, the relative amount of magnetite in ferritin containing 2200 to 200 iron atoms rose steadily from ~20% to ~70% whereas the percentage of ferrihydrite fell from ~60% to ~20%. These results indicate a ferrihydrite-magnetite core-shell structure. It was also found that the magnetite in the ferritin iron core is not a source of free toxic ferrous iron, as previously believed. Therefore, the presence of magnetite in the ferritin cores of patients with Alzheimer’s disease is not a cause of their increased brain iron(II) concentration.