Mössbauer spectroscopy applied to the oxidized and semi-reduced states of the iron-molybdenum cofactor of nitrogenase.
Mössbauer parameters at 125K for both the oxidized and semi-reduced states of FeMoco isolated from the MoFe protein of Azotobacter vinelandii nitrogenase of delta/Fe = 0.32 and 0.37 mm/s and delta Eq = 0.84 and 0.71 mm/s, respectively, are reported. FeMoco(ox) fits the Debye model perfectly from 4.2-125K and has a S = 0 ground state. FeMoco(ox) apparently contains 10-20% FeMoco(s-r) and vice versa, possibly as a result of the spontaneous oxidation phenomenon. Quantitation of the spectra indicates a Fe:Mo ratio of 5 +/- 1:1 and the similar quadrupole splittings and isomer shifts suggest a similar environment for all iron atoms.
Western Regional Research Center, USDA-ARS, Albany, CA 94710.
W E
WE
Newton
S F
SF
Gheller
R H
RH
Sands
W R
WR
Dunham
D001395:Azotobacter / Q000201:enzymology*; D005288:Ferredoxins / Q000032:analysis*; D007501:Iron / Q000032:analysis; D008982:Molybdenum / Q000032:analysis; D008983:Molybdoferredoxin / Q000032:analysis*; D009591:Nitrogenase / Q000032:analysis*; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer
D005288:Ferredoxins; D008983:Molybdoferredoxin; D008982:Molybdenum; D007501:Iron; D009591:Nitrogenase