New structural insights into the iron-molybdenum cofactor from azotobacter vinelandii nitrogenase through sulfur K and molybdenum L x-ray absorption edge studies

Journal Article · Wed Jun 08 04:00:00 EDT 1988 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00220a013· OSTI ID:7003566

Hedman, B; Frank, P; Gheller, S F; Roe, A L; Newton, W E; Hodgson, K O

The electronic and structural nature of sulfur and molybdenum in the FeMO cofactor (FeMO-co) isolated from Azotobacter vinelandii MoFe protein has been studied by X-ray absorption edge and near-edge spectroscopy (referred to herein collectively as XANES) at the sulfur K and molybdenum L/sub 3/ and L/sub 2/ absorption edges. In contrast to the relatively poor resolution found for X-ray absorption edges at higher energies (e.g., several electronvolts at the molybdenum K edge at 20 keV), resolution in the 2.5-3.0-keV region is significantly improved (e.g., 0.5 eV at the sulfur K edge at 2.47 keV), resulting in more edge structure with higher sensitivity to changes in electronic and structural environment. In order to record spectra from dilute samples at these low energies, an experimental method that takes advantage of the higher flux synchrotron radiation from an undulator magnet has been developed. XANES spectra have been recorded for FeMo-co in the oxidized (ox) and semireduced (s-r) forms and, for comparison, a number of inorganic complexes containing molybdenum and sulfur. To remove the interference of dithionite, its decomposition products, and other small, unbound molecules from the FeMo-co spectrum, an anaerobic column chromatographic method of purification has been developed. The spectrum of dithionite-free FeMo-co in the oxidized form could thus be recorded.

• Research Organization: Stanford Synchrotron Radiation Lab., CA (USA)
• OSTI ID: 7003566
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:12; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
AZOTOBACTER
BACTERIA
DATA
ELECTROMAGNETIC RADIATION
ELECTRONIC STRUCTURE
ELEMENTS
ENZYMES
EXPERIMENTAL DATA
INFORMATION
IONIZING RADIATIONS
IRON
METALS
MICROORGANISMS
MOLYBDENUM
NITRO-GROUP DEHYDROGENASES
NITROGENASE
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PROTEINS
RADIATIONS
SPECTROSCOPY
TRANSITION ELEMENTS
X RADIATION