Aleksandrov Alexey, Bonvalet Adeline, Müller Pavel, Sorigué Damien, Beisson Fred, Antonucci Laura, Solinas Xavier, Joffre Manuel, Vos Marten H
LOB, CNRS, INSERM, École Polytechnique, Institut Polytechnique de Paris, 91120, Palaiseau, France.
Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
Angew Chem Int Ed Engl. 2024 May 6;63(19):e202401376. doi: 10.1002/anie.202401376. Epub 2024 Mar 28.
In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO⋅ from fatty acid RCOO occurs in 300 ps, upon which CO 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.
在脂肪酸光脱羧酶（FAP）中，脂肪酸RCOO在光照下300皮秒内形成初级自由基产物RCOO⋅，随后CO几乎立即释放。基于脂肪族RCOO⋅（由于不稳定而未进行光谱表征）与芳族羰氧基自由基（如2,6-二氯苯甲酰氧基自由基（DCB⋅））类似在红光区吸收的假设，最近有人提出了寿命长得多的线性RCOO⋅。我们进行了量子化学反应途径和光谱计算。这些计算结果与实验测得的DCB⋅脱羧动力学和光谱性质相符，结果表明，与DCB⋅不同，脂肪族RCOO⋅自由基a）以非常低的能垒在几皮秒的时间尺度上脱羧，且b）几乎没有红光吸收。时间分辨红外光谱实验证实了FAP中RCOO⋅的脱羧非常迅速，小于300皮秒。我们认为，这一特性是FAP中观察到的高碳氢化合物形成量子产率所必需的。
