Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology , Okayama University , Okayama 700-8530 , Japan.
Graduate School of Science , Kobe University , Kobe 657-8501 , Japan.
J Phys Chem B. 2019 Mar 28;123(12):2673-2678. doi: 10.1021/acs.jpcb.8b12086. Epub 2019 Mar 15.
Fucoxanthin chlorophyll (Chl) a/ c-binding proteins (FCPs) are unique light-harvesting antennas in diatoms. Recent time-resolved fluorescence analysis of photosystem I with FCP associated (PSI-FCPI) has mainly shown excitation energy transfer among Chls a from FCPI to PSI in tens of picoseconds. However, it remains unclear how each pigment, especially carotenoids and Chl c, in the FCPI is functionally related to the energy transfer in a femtosecond time range. Here, we reveal ultrafast excitation energy transfer mechanism in the PSI-FCPI preparations isolated from a diatom, Chaetoceros gracilis, by means of femtosecond time-resolved fluorescence spectroscopy with an upconversion system. Compared with the fluorescence lifetime components of PSI core-like complexes, the energy transfer of Chl c → Chl a in the FCPI was observed within hundreds of femtoseconds, and the energy in the FCPI was transferred to PSI in ∼2 ps. The comparative fluorescence analyses provide physical insights into the energy transfer machinery within FCPI and from FCPI to PSI.
褐藻素叶绿素（Chl）a/c 结合蛋白（FCPs）是硅藻中独特的光捕获天线。最近，与 FCP 相关的光系统 I 的时间分辨荧光分析（PSI-FCPI）主要显示了 FCPI 中的 Chl a 之间在几十皮秒内的激发能量转移。然而，每个色素，特别是类胡萝卜素和 Chl c，在 FCPI 中如何与飞秒时间范围内的能量转移功能相关仍然不清楚。在这里，我们通过上转换系统的飞秒时间分辨荧光光谱法，揭示了从硅藻角毛藻中分离出的 PSI-FCPI 制剂中的超快激发能量转移机制。与 PSI 核心样复合物的荧光寿命成分相比，FCPI 中 Chl c→Chl a 的能量转移在几百飞秒内观察到，并且 FCPI 中的能量在约 2 ps 内转移到 PSI。比较荧光分析为 FCPI 内和从 FCPI 到 PSI 的能量转移机制提供了物理见解。
