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Title: Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies

Abstract

Mo nitrogenase (N 2ase) utilizes a two-component protein system, the catalytic MoFe and its electron-transfer partner FeP, to reduce atmospheric dinitrogen (N 2) to ammonia (NH 3). 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 N 2. This field of chemistry has relied heavily on the detailed characterization of how Mo N 2ase accomplishes this feat. Understanding the reaction mechanism of Mo N 2ase 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, E 1, 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 absorptionmore » and 57Fe Mössbauer spectroscopies, we correlate a previously reported unique species formed under cryoreducing conditions to the natively formed E 1 state through annealing, demonstrating the viability of cryoreduction in studying the catalytic intermediates of MoFe.« less

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [4]; ORCiD logo [4]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34−36, 45470 Mülheim an der Ruhr, Germany
  2. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
  3. Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
  4. Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
Publication Date:
Research Org.:
Max Planck Society, Mülheim (Germany); Utah State Univ., Logan, UT (United States); Stanford Univ., CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Institutes of Health (NIH); National Science Foundation (NSF)
OSTI Identifier:
1558699
Alternate Identifier(s):
OSTI ID: 1562298
Grant/Contract Number:  
DESC0010687; AC02-76SF00515; SC0010687; GM111097; CHE1654060
Resource Type:
Journal Article: Published Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Name: Inorganic Chemistry Journal Volume: 58 Journal Issue: 18; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Van Stappen, Casey, Davydov, Roman, Yang, Zhi-Yong, Fan, Ruixi, Guo, Yisong, Bill, Eckhard, Seefeldt, Lance C., Hoffman, Brian M., and DeBeer, Serena. Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b01951.
Van Stappen, Casey, Davydov, Roman, Yang, Zhi-Yong, Fan, Ruixi, Guo, Yisong, Bill, Eckhard, Seefeldt, Lance C., Hoffman, Brian M., & DeBeer, Serena. Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies. United States. doi:10.1021/acs.inorgchem.9b01951.
Van Stappen, Casey, Davydov, Roman, Yang, Zhi-Yong, Fan, Ruixi, Guo, Yisong, Bill, Eckhard, Seefeldt, Lance C., Hoffman, Brian M., and DeBeer, Serena. Fri . "Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies". United States. doi:10.1021/acs.inorgchem.9b01951.
@article{osti_1558699,
title = {Spectroscopic Description of the E 1 State of Mo Nitrogenase Based on Mo and Fe X-ray Absorption and Mössbauer Studies},
author = {Van Stappen, Casey and Davydov, Roman and Yang, Zhi-Yong and Fan, Ruixi and Guo, Yisong and Bill, Eckhard and Seefeldt, Lance C. and Hoffman, Brian M. and DeBeer, Serena},
abstractNote = {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.},
doi = {10.1021/acs.inorgchem.9b01951},
journal = {Inorganic Chemistry},
issn = {0020-1669},
number = 18,
volume = 58,
place = {United States},
year = {2019},
month = {8}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.inorgchem.9b01951

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Cited by: 4 works
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Figures / Tables:

Scheme 1 Scheme 1: Current Proposed Relationship between the Previously Observed Natively Reduced (MR) and Cryoreduced (MI) Species Formed at the FeMoco Cluster

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