ELECTRON-ENERGY-LOSS SPECTROSCOPY STUDY OF IRON DEPOSITION IN HUMAN ALVEOLAR MACROPHAGES - FERRITIN OR HEMOSIDERIN

Electron energy loss spectroscopy imaging (EELSI) was used to obtain Fe maps, with molecular resolution, in human alveolar macrophages. Fe concentrations were found in particular structures named siderosomes. The combined application of Extended energy loss fine structure (EXELFS) analysis, a ''short-range'' probe, and Selected area electron diffraction (SAED), a ''long-range'' probe, allowed us to investigate the atomic arrangement of proteins constituting the siderosomes. Results are compared with structural data obtained on purified proteins. It is found that the siderosomes seem to be constituted mainly by normal hemosiderins.