Ferritin magnetic properties

R.E. Spitzer, C.R. (1977) The Viking magnetic properties experiment Primary mission results. J. Geophys. Res. 82 4547-4558 Harrison, J.B. Berkheiser,V.E. (1982) Anion interactions with freshly prepared hydrous iron oxides. Clays Clay Min. 30 97-102 Harrison, P.M. HoyT.G. (1973) Ferritin. In Eichhom, G.L. (ed.) Inorganic biochemistry. 

St. Pierre, T. G. Chan, R Bauchspiess, K. R. Webb, J. Betteridge, S. Walton, S. Dickson, D. P. E. Synthesis, structure and magnetic properties of ferritin cores with varying composition and degrees of structural order models for iron oxide deposits in iron-overload diseases. Coord. Chem. Rev. 1996, 151, 125-143. 

S.L. Daniel, J.N. Ngunjiri, and J.C. Gamo, Investigation of the magnetic properties of ferritin by AFM imaging with magnetic sample modulation. Aruil. Bioanal. Chem., 394, 215-223 (2009). 

Again, the enzyme urease was found to contain a dimeric nickel(II) center based only on its magnetic properties (eqn [10] with 5=1). In large proteins such as ferritin, strong coupling is seen in a Fe-O-phosphate center, rather like a small piece of rust enclosed in a protein sheath. Likewise, nitrogenases contain a number of linked irons. 

Papaefthymiou outlined possible directions of future Mossbauer studies in the most recent review [130]. Among them there is a study on magnetic properties that up to now reported about differences in ferritin particles behavior. It is not clear yet whether iron storage conditions and the iron core structure influenced the magnetic properties of ferritin. 

There is a number of synthetic substitutes for natural ferritin and the properties of these have been compared with those of ferritin. The synthetic polysaccharide iron complex (PIC), has a magnetic blocking temperature of 48K (Mohie-Eldin et al. 1994). Iron-dextran complexes are used as a substitute for ferritin in the treatment of anaemia. The iron cores of these complexes consist not of ferrihydrite, but of very poorly crystalline akaganeite with magnetic blocking temperatures of between 150 and 290 K (Muller, 1967 Knight et al. 1999) which were lowered from 55K to 35 and 25K, if prepared in the presence of 0.250 and 0.284 Al/(A1 -i- Fe), respectively (Cheng et al.2001). 

Other physical properties also show that the iron cores of native ferritins and bacterioferritins are different. Mossbauer spectra of ferritins measured as a function of temperature (Fig. 1) show quadrupole split doublets, with an isomer shift typical of Fe +, gradually being replaced as the temperature is lowered (between about 50 and 15 K) by a magnetic hyperfine spectrum (30, 31). The transition temperature, Tb, is lower than the ordering temperature, Tord (240 K) observed for bulk ferrihydrite (32), because of fluctuations in the direction of mag-... 

X-ray scattering, Mossbauer spectroscopy, infrared spectroscopy and magnetic susceptibility studies on the ferric hydroxynitrate polymer (approximate composition Fe4C>3(OH)4 (NC>3)2 1.5 H2O) shows that it is closely similar in those properties to the core of ferritin (180). It was also reported (72) that ferritin prepared from Fe2+ and apoferritin under oxidising conditions had a different morphology from native ferritin the iron micelle had a diameter of 48 A instead of 70 A and the overall diameter was 102 A instead of 120 A. 

Until recently, all ferritin cores were thought to be microcrystalline and to be the same. However, x-ray absorption spectroscopy, Mossbauer spectroscopy, and high-resolution electron microscopy of ferritin from different sources have revealed variations in the degree of structural and magnetic ordering and/or the level of hydration. Structural differences in the iron core have been associated with variations in the anions present, e.g., phosphate or sulfate, and with the electrochemical properties of iron. Anion concentrations in turn could reflect both the solvent composition and the properties of the protein coat. To understand iron storage, we need to define in more detail the relationship of the ferritin protein coat and the environment to the redox properties of iron in the ferritin core. 

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