RESUMO
In a previous study of human haemosiderin and ferritin by a combination of Mössbauer spectroscopy and electron microscopy, it was observed that the Mössbauer spectra of haemosiderin showed a very different temperature dependence to those of ferritin. These differences were related to the superparamagnetic behaviour of small particles of a magnetic material and suggested that the magnetic anisotropy constant of the haemosiderin was considerably larger than that of the ferritin. In the present work, samples of ferritin have been examined by Mössbauer spectroscopy following partial deproteinisation, subfractionation, and reconstitution with and without phosphate, in order to investigate whether these procedures lead to changes in the magnetic anisotropy constant of the iron-containing cores. There is no evidence from the present data that changes in the protein shell, in the size of the iron-containing cores of ferritin, or in the phosphate content lead to any significant changes in the magnetic anisotropy constant, as obtained from the temperature dependence of the Mössbauer spectra. These results indicate that the different magnetic anisotropy constant observed in the case of human haemosiderin resulting from transfusional iron overload must arise from other significant differences in the composition or structure of the iron-containing cores.