Long-Lived Hydrated FMN Radicals: EPR Characterization and Implications for Catalytic Variability in Flavoproteins.
J Am Chem Soc
; 140(48): 16521-16527, 2018 12 05.
Article
en En
| MEDLINE
| ID: mdl-30412389
Until now, FMN/FAD radicals could not be stabilized in aqueous solution or other protic solvents because of rapid and efficient dismutation reactions. In this contribution, a novel system for stabilizing flavin radicals in aqueous solution is reported. Subsequent to trapping FMN in an agarose matrix, light-generated FMN radicals could be produced that were stable for days even under aerobic conditions, and their concentrations were high enough for extensive EPR characterization. All large hyperfine couplings could be extracted by using a combination of continuous-wave EPR and low-temperature ENDOR spectroscopy. To map differences in the electronic structure of flavin radicals, two exemplary proton hyperfine couplings were compared with published values from various neutral and anionic flavoprotein radicals: C(6)H and C(8α)H 3. It turned out that FMNâ¢- in an aqueous environment shows the largest hyperfine couplings, whereas for FMNH⢠under similar conditions, hyperfine couplings are at the lower end and the values of both vary by up to 30%. This finding demonstrates that protein-cofactor interactions in neutral and anionic flavoprotein radicals can alter their electron spin density in different directions. With this aqueous system that allows the characterization of flavin radicals without protein interactions and that can be extended by using selective isotope labeling, a powerful tool is now at hand to quantify interactions in flavin radicals that modulate the reactivity in different flavoproteins.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Mononucleótido de Flavina
/
Radicales Libres
Idioma:
En
Revista:
J Am Chem Soc
Año:
2018
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Estados Unidos