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 F e maps, with molecular resolution, in human alveolar macrophages. Fe c oncentrations were found in particular structures named siderosomes. T he combined application of Extended energy loss fine structure (EXELFS ) analysis, a ''short-range'' probe, and Selected area electron diffra ction (SAED), a ''long-range'' probe, allowed us to investigate the at omic arrangement of proteins constituting the siderosomes. Results are compared with structural data obtained on purified proteins. It is fo und that the siderosomes seem to be constituted mainly by normal hemos iderins.