Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies
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- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34−36, 45470 Mülheim an der Ruhr, Germany
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
Mo nitrogenase (N2ase) utilizes a two-component protein system, the catalytic MoFe and its electron-transfer partner FeP, to reduce atmospheric dinitrogen (N2) to ammonia (NH3). The FeMo cofactor contained in the MoFe protein serves as the catalytic center for this reaction and has long inspired model chemistry oriented toward activating N2. This field of chemistry has relied heavily on the detailed characterization of how Mo N2ase accomplishes this feat. Understanding the reaction mechanism of Mo N2ase itself has presented one of the most challenging problems in bioinorganic chemistry because of the ephemeral nature of its catalytic intermediates, which are difficult, if not impossible, to singly isolate. This is further exacerbated by the near necessity of FeP to reduce native MoFe, rendering most traditional means of selective reduction inept. We have now investigated the first fundamental intermediate of the MoFe catalytic cycle, E1, as prepared both by low-flux turnover and radiolytic cryoreduction, using a combination of Mo Kα high-energy-resolution fluorescence detection and Fe K-edge partial-fluorescence-yield X-ray absorption spectroscopy techniques. The results demonstrate that the formation of this state is the result of an Fe-centered reduction and that Mo remains redoxinnocent. Furthermore, using Fe X-ray absorption and 57Fe Mössbauer spectroscopies, we correlate a previously reported unique species formed under cryoreducing conditions to the natively formed E1 state through annealing, demonstrating the viability of cryoreduction in studying the catalytic intermediates of MoFe.
- Research Organization:
- Max Planck Society, Mülheim (Germany); Utah State Univ., Logan, UT (United States); Stanford Univ., CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); National Institutes of Health (NIH); National Science Foundation (NSF)
- Grant/Contract Number:
- DESC0010687; AC02-76SF00515; SC0010687; GM111097; CHE1654060
- OSTI ID:
- 1558699
- Alternate ID(s):
- OSTI ID: 1562298
- Journal Information:
- Inorganic Chemistry, Journal Name: Inorganic Chemistry Vol. 58 Journal Issue: 18; ISSN 0020-1669
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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journal | January 2020 |
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journal | January 2020 |
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journal | January 2019 |
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