Department of Applied Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, 669-1337, Japan.
Faraday Discuss. 2017 Jun 2;198:59-71. doi: 10.1039/c6fd00211k.
Fucoxanthin is a carotenoid that is mainly found in light-harvesting complexes from brown algae and diatoms. Due to the presence of a carbonyl group attached to polyene chains in polar environments, excitation produces an excited intra-molecular charge transfer. This intra-molecular charge transfer state plays a key role in the highly efficient (∼95%) energy-transfer from fucoxanthin to chlorophyll a in the light-harvesting complexes from brown algae. In purple bacterial light-harvesting systems the efficiency of excitation energy-transfer from carotenoids to bacteriochlorophylls depends on the extent of conjugation of the carotenoids. In this study we were successful, for the first time, in incorporating fucoxanthin into a light-harvesting complex 1 from the purple photosynthetic bacterium, Rhodospirillum rubrum G9+ (a carotenoidless strain). Femtosecond pump-probe spectroscopy was applied to this reconstituted light-harvesting complex in order to determine the efficiency of excitation energy-transfer from fucoxanthin to bacteriochlorophyll a when they are bound to the light-harvesting 1 apo-proteins.
岩藻黄质是一种类胡萝卜素，主要存在于褐藻和硅藻的光捕获复合物中。由于在极性环境中，羰基与多烯链相连，激发会产生分子内激发电荷转移。这种分子内电荷转移状态在从褐藻光捕获复合物中的岩藻黄质到叶绿素 a 的高效（约 95%）能量转移中起着关键作用。在紫色细菌光捕获系统中，类胡萝卜素到细菌叶绿素的激发能量转移效率取决于类胡萝卜素的共轭程度。在这项研究中，我们首次成功地将岩藻黄质掺入来自紫色光合细菌 Rhodospirillum rubrum G9+（一种不含类胡萝卜素的菌株）的光捕获复合物 1 中。飞秒泵浦探针光谱学被应用于这种重组的光捕获复合物，以确定当它们与光捕获 1 脱辅基蛋白结合时，岩藻黄质到细菌叶绿素 a 的激发能量转移效率。
