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Carotenoid Singlet Fission Reactions in Bacterial Light Harvesting Complexes As Revealed by Triplet Excitation Profiles
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-10-26 00:00:00 , DOI: 10.1021/jacs.7b09809 Jie Yu 1 , Li-Min Fu 1 , Long-Jiang Yu 2, 3 , Ying Shi 1 , Peng Wang 1 , Zheng-Yu Wang-Otomo 2 , Jian-Ping Zhang 1
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-10-26 00:00:00 , DOI: 10.1021/jacs.7b09809 Jie Yu 1 , Li-Min Fu 1 , Long-Jiang Yu 2, 3 , Ying Shi 1 , Peng Wang 1 , Zheng-Yu Wang-Otomo 2 , Jian-Ping Zhang 1
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Carotenoids (Cars) in bacterial photosynthesis are known as accessory light harvesters and photoprotectors. Recently, the singlet fission (SF) reaction initiated by Car photoabsorption has been recognized to be an effective excitation deactivation channel disfavoring the light harvesting function. Since the SF reaction and the triplet sensitization reaction underlying photoprotection both yield triplet excited state Cars (3Car*), their contribution to the overall 3Car* photoproduction are difficult to disentangle. To tackle this problem, we resorted to the triplet excitation profiles (TEPs), i.e., the actinic spectra of the overall 3Car* photoproduction. The TEPs combined with the conventional fluorescence excitation spectra allowed us to extract the neat SF contribution, which can serve as a spectroscopic measure for the SF reactivity. This novel spectroscopic strategy was applied to analyze the light harvesting complexes (LHs) from Tch. tepidum and Rba. sphaeroides 2.4.1. The results unambiguously showed that the SF reaction of Cars proceeds with an intramolecular scheme, even in the case of LH1-RC from Rba. sphaeroides 2.4.1 likely binding a secondary pool of Cars. Regarding the SF-reactivity, the geometric distortion in the conjugated backbone of Cars was shown to be the structural determinant, while the length of the Car conjugation was suggested to be relevant to the effective localization of the geminate triplets to avoid being annihilated. The SF reaction scheme and structure–activity relationship revealed herein will be useful not only in deepening our understanding of the roles of Cars in photosynthesis, but also in enlightening the applications of Cars in artificial light conversion systems.
中文翻译：
通过三重态激发曲线揭示细菌光收集复合物中的类胡萝卜素单线态裂变反应
细菌光合作用中的类胡萝卜素（Cars）被称为辅助光收集器和光保护剂。最近，由汽车光吸收引发的单线裂变（SF）反应已被认为是不利于光收集功能的有效激发失活通道。由于SF反应和受光保护作用的三重态敏化反应均会产生三重态激发态Cars（3 Car *），因此它们对整个3 Car *光产生的贡献很难分解。为了解决这个问题，我们求助于三重激发态（TEP），即整个3汽车*照片制作。TEP与常规荧光激发光谱相结合，使我们能够提取纯净的SF贡献，可以用作SF反应性的光谱测量。这种新颖的光谱策略被应用于分析来自Tch的光收集复合物（LHs）。tepidum和Rba。球茎2.4.1。结果清楚地表明，即使在来自Rba的LH1-RC的情况下，Cars的SF反应仍采用分子内方案进行。球菌2.4.1可能绑定二级汽车池。关于SF反应性，Cars共轭骨架中的几何变形被证明是结构决定因素，而Car共轭的长度被认为与双胞胎三胞胎的有效定位有关，以避免被消灭。此处揭示的SF反应方案和结构-活性关系不仅有助于加深我们对汽车在光合作用中的作用的理解，而且有助于启发汽车在人造光转换系统中的应用。
更新日期：2017-10-27
中文翻译：
通过三重态激发曲线揭示细菌光收集复合物中的类胡萝卜素单线态裂变反应
细菌光合作用中的类胡萝卜素（Cars）被称为辅助光收集器和光保护剂。最近，由汽车光吸收引发的单线裂变（SF）反应已被认为是不利于光收集功能的有效激发失活通道。由于SF反应和受光保护作用的三重态敏化反应均会产生三重态激发态Cars（3 Car *），因此它们对整个3 Car *光产生的贡献很难分解。为了解决这个问题，我们求助于三重激发态（TEP），即整个3汽车*照片制作。TEP与常规荧光激发光谱相结合，使我们能够提取纯净的SF贡献，可以用作SF反应性的光谱测量。这种新颖的光谱策略被应用于分析来自Tch的光收集复合物（LHs）。tepidum和Rba。球茎2.4.1。结果清楚地表明，即使在来自Rba的LH1-RC的情况下，Cars的SF反应仍采用分子内方案进行。球菌2.4.1可能绑定二级汽车池。关于SF反应性，Cars共轭骨架中的几何变形被证明是结构决定因素，而Car共轭的长度被认为与双胞胎三胞胎的有效定位有关，以避免被消灭。此处揭示的SF反应方案和结构-活性关系不仅有助于加深我们对汽车在光合作用中的作用的理解，而且有助于启发汽车在人造光转换系统中的应用。
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