Catalytic mechanism of fatty acid photodecarboxylase: on the detection and stability of the initial carbonyloxy radical intermediate
Résumé
In fatty acid photodecarboxylase (FAP), light‐induced formation of the primary radical product RCOO$^●$ from fatty acid RCOO– occurs in 300 ps, upon which CO2 is released quasi‐immediately. Based on the hypothesis that aliphatic RCOO$^●$ (spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6‑dichlorobenzoyloxy radical (DCB$^●$), much longer‐lived linear RCOO$^●$ has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. These calculations are in line with the experimental DCB$^●$decarboxylation dynamics and spectral properties and show that in contrast to DCB$^●$, aliphatic RCOO$^●$ radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time‐resolved infrared spectroscopy experiment confirms very rapid, <<300 ps RCOO$^●$ decarboxylation in FAP. We argue that this property is required for the observed high quantum yield of hydrocarbons formation by FAP.
| Origine | Fichiers éditeurs autorisés sur une archive ouverte |
|---|