Department of Physics and Astronomy, Aarhus University, 8000 Aarhus, Denmark.
Department of Chemistry, University of Copenhagen, 2100 Copenhagen Ø, Denmark.
J Phys Chem Lett. 2023 Jun 29;14(25):5949-5954. doi: 10.1021/acs.jpclett.3c01206. Epub 2023 Jun 22.
Bioluminescence from fireflies, click beetles, and railroad worms ranges in color from green-yellow to orange to red. The keto form of oxyluciferin is considered a key emitter species in the proposed mechanisms to account for color variation. To establish the intrinsic photophysics in the absence of a microenvironment, we present experimental and theoretical gas-phase absorption and emission spectra of the 5,5-dimethyloxyluciferin anion (keto form) at room and cryogenic temperatures as well as lifetime measurements based on fluorescence. The theoretical model includes all 75 vibrational modes. The spectral impact of the large number of excited states at elevated temperatures is captured by an effective state distribution. At low temperature, spectral congestion is greatly reduced, and the observed well-resolved vibrational features are assigned to multiple Franck-Condon progressions involving different vibrational modes. An in-plane ∼60 cm scissoring mode is found to be involved in the dominant progressions.
萤火虫、叩头虫和铁路蠕虫的生物发光颜色范围从绿黄色到橙色到红色。氧杂环丁烷酮形式的氧化荧光素被认为是解释颜色变化的拟议机制中的关键发射物种。为了在不存在微环境的情况下确定内在光物理性质，我们在室温下和低温下展示了 5,5-二甲基氧杂环丁烷酮阴离子（酮式）的实验和理论气相吸收和发射光谱以及基于荧光的寿命测量。理论模型包括所有 75 个振动模式。通过有效态分布来捕获高温下大量激发态对光谱的影响。在低温下，光谱拥挤大大减少，观察到的分辨率良好的振动特征被分配到涉及不同振动模式的多个 Franck-Condon 进展中。发现平面内约 60 cm 的剪式振动模式参与了主要的进展。
