Cubane-type clusters structural parameters

The structures of the active sites of 4-Fe and 8-Fe Ferredoxins has been univocally established by X-ray diffraction methods. Proteins of the 4-Fe type contain the [Fe4S4(S-Cys)4] site with a cubane-like structure as that illustrated schematically in Fig. 5.2. The structure of HP from Chromatium vinosum has been determined for two oxidation levels, HP ed and HPox- In both cases the active sites are tetranuclear clusters as shown in Fig. 5.2. Characteristic structural parameters for such centers can be observed in Fig. 5.3 where they are reproduced beside those of some synthetic analogues. As illustrated in Fig. 5.4, in the 8-Fe Fdox from Peptococcus aerogenes there are-two identical tetranuclear active centers which are separated by about 12 A. They are dimensionally very similar to the site in HP ed-... 

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