Ferritin, Mossbauer spectra

Other physical parameters of the micelle also suggest that the cores of ferritin and ferric nitrate polymer are closely related. The magnetic susceptibility of the iron micelle is 3.84 Bohr magnetons. The Mossbauer spectrum for ferritin observed by Boas and Window (39) and by Blaise et al. 40) are in close agreement with the spectrum for the ferric nitrate polymer as well as the ferric citrate and ferric fructose polymers. Most interesting is the fact that the size of the ferric hydroxide polymer in the ferritin molecule is practically identical to that observed for the ferric nitrate and ferric citrate spheres. 

The similarity between the Mossbauer parameters of ferritin and a synthetic polymer derived from hydrolysed ferric nitrate have been pointed out previously (101) the polymer has a similar room temperature Mossbauer spectrum with isomer shift and quadropole splitting of 0.48 and 0.67 mm/sec. respectively. At very low temperatures the spectrum of the polymer is also closely similar to ferritin. 

Figure 5.2 The influence of magnetic interaction with respect to the excited nuclear state of Fe. (From Schiinemann and Winkler. ) The influence of magnetic interaction with respect to the excited nuclear state of Fe. The latter splits into four sublevels. The selection rule for magnetic dipole (Ml) transitions (AI = 1 and AMi = 0, 1) yields the observed six-line pattern, (a) The Mossbauer spectrum of a metaUic iron foil, (b) The Mossbauer spectrum of the iron carrier protein ferritin. 2000 lOP Publishing Ltd.

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-... 

Figure 8.9 Mossbauer spectra obtained from Fe-loaded human NM exhibits a doublet at 300 K (a) and a sextet (92%) at 4.2 K (c) characteristic of trivalent iron. The spectrum at 120 K exhibits superparamagnetic relaxation, indicative of ferritin-like iron clusters (b). The spectrum at 4.2 K was measured in an externally applied field of 20 mT, applied parallel to the gamma beam. (Reprinted from Double et 2003 Elsevier Science Inc.)...

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