| Autor: |
Jiang H; Department of Computational Chemistry, Lund University, Chemical Centre, P.O. Box 124, Lund SE-221 00, Sweden., Lundgren KJM; Department of Computational Chemistry, Lund University, Chemical Centre, P.O. Box 124, Lund SE-221 00, Sweden., Ryde U; Department of Computational Chemistry, Lund University, Chemical Centre, P.O. Box 124, Lund SE-221 00, Sweden. |
| Jazyk: |
angličtina |
| Zdroj: |
Inorganic chemistry [Inorg Chem] 2023 Dec 04; Vol. 62 (48), pp. 19433-19445. Date of Electronic Publication: 2023 Nov 21. |
| DOI: |
10.1021/acs.inorgchem.3c02329 |
| Abstrakt: |
Nitrogenase is the only enzyme that can cleave the strong triple bond in N 2 , making nitrogen available for biological life. There are three isozymes of nitrogenase, differing in the composition of the active site, viz., Mo, V, and Fe-nitrogenase. Recently, the first crystal structure of Fe-nitrogenase was presented. We have performed the first combined quantum mechanical and molecular mechanical (QM/MM) study of Fe-nitrogenase. We show with QM/MM and quantum-refinement calculations that the homocitrate ligand is most likely protonated on the alcohol oxygen in the resting E 0 state. The most stable broken-symmetry (BS) states are the same as for Mo-nitrogenase, i.e., the three Noodleman BS7-type states (with a surplus of β spin on the eighth Fe ion), which maximize the number of nearby antiferromagnetically coupled Fe-Fe pairs. For the E 1 state, we find that protonation of the S2B μ 2 belt sulfide ion is most favorable, 14-117 kJ/mol more stable than structures with a Fe-bound hydride ion (the best has a hydride ion on the Fe2 ion) calculated with four different density-functional theory methods. This is similar to what was found for Mo-nitrogenase, but it does not explain the recent EPR observation that the E 1 state of Fe-nitrogenase should contain a photolyzable hydride ion. For the E 1 state, many BS states are close in energy, and the preferred BS state differs depending on the position of the extra proton and which density functional is used. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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