The structure of ferritin cores determined by electron nanodiffraction

Electron nanodiffraction, with a 100-keV electron beam less than 1 nm in diameter, has been used to obtain single-crystal diffraction patterns from individual iron-containing cores of ferritin molecules. We show that, while a majority of the cores have a hexagonal structure somewhat similar to the major phase in the mineral ferrihydrite, as previously assumed, several minor phases are present including some that are similar in structure to the iron oxides magnetite and hematite and also some composed of highly disordered material. In general, each core consists of one single crystal of one phase.