FeMo protein Mossbauer spectrum

FeMoco, both as a constituent of the FeMo protein and an isolated entity, has been the subject of detailed spectroscopic examination. 57Fe Mossbauer and EPR studies of the cofactor have been interpreted in terms of an S = centre that contains one molybdenum and ca. six irons in a spin-coupled structure. The EPR signal serves as a valuable fingerprint of FeMoco furthermore, release of FeMoco from the FeMo protein produces an EPR spectrum with broader features, but the same profile, thereby indicating that the core of this cluster is little changed by the extraction procedure. Treatment of FeMoco with ca. one equivalent of... 

Mossbauer spectrum of C. pasteurianum nitrogenase FeMo protein,indicating the various components (quadrupole doublets) and their assignments. The doublet labeled M is the cofactor signal those labeled D, S, and Fe + are attributed to the P-clusters. 

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