Ferritin core analog

A variety of approaches have been adopted in attempts to obtain analogs of crystalline ferritin cores but, as Powell has pointed out, uncertainty over the structure of the ferritin core itself complicates this field. The earliest synthetic approach was that of Spiro et al., who obtained citrate-coated spheres of polymeric iron hydroxide by hydrolysis of ferric citrate. Though the early characterization of these spheres indicated they might be good models for ferritin, the difficulty in obtaining reproducible samples, and the lack of structural information, has led to greater efforts being put into other approaches. 

Our electronic absorption spectral studies on the ferritin core itself are less definitive (8, 9). Because of strong tail absorption through the visible, we have been able to resolve only a 918-nm LF band. This band is diagnostic of [Fe(III)06]oct coordination, but without better spectra in the 400-700-nm region we cannot distinguish between exclusively [Fe(lII)06]oct and mixed [Fe(III)06]oct-[Fe(III)04]tet coordination structures. There is, however, no positive evidence for the presence of [Fe(III)04]tet units in the core and the analogy with the Saltman-Spiro ball leads us to prefer a model with [Fe(III)06]oct coordination. 

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