Nitrogenase Chemistry at 10 KelvinâPhototautomerization and Recombination of CO-Inhibited α-H195Q Enzyme.
Inorg Chem
; 61(30): 11509-11513, 2022 Aug 01.
Article
in En
| MEDLINE
| ID: mdl-35856737
ABSTRACT
CO-bound forms of nitrogenase are N2-reduction inhibited and likely intermediates in Fischer-Tropsch chemistry. Visible-light photolysis at 7 K was used to interrogate all three known CO-related EPR-active forms as exhibited by the α-H195Q variant of Azotobacter vinelandii nitrogenase MoFe protein. The hi(5)-CO EPR signal converted to the hi-CO EPR signal, which reverted at 10 K. FT-IR monitoring revealed an exquisitely light-sensitive "Hi-2" species with bands at 1932 and 1866 cm-1 that yielded "Hi-1" with bands at 1969 and 1692 cm-1, which reverted to "Hi-2". The similarities of photochemical behavior and recombination kinetics showed, for the first time, that hi-CO EPR and "Hi-1" IR signals arise from one chemical species. hi(5)-CO EPR and "Hi-2" IR signals are from a second species, and lo-CO EPR and "Lo-2" IR signals, formed after prolonged illumination, are from a third species. Comparing FT-IR data with CO-inhibited MoFe-protein crystal structures allowed assignment of CO-bonding geometries in these species.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Azotobacter vinelandii
/
Nitrogenase
Language:
En
Journal:
Inorg Chem
Year:
2022
Type:
Article
Affiliation country:
United States