Department of Physics, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05 České Budějovice, Czech Republic.
Department of Chemical Physics and Optics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic.
J Phys Chem Lett. 2021 Apr 1;12(12):3176-3181. doi: 10.1021/acs.jpclett.1c00122. Epub 2021 Mar 23.
Femtosecond transient absorption spectroscopy following two-photon excitation (2PE) is used to determine the contributions of carotenoids and chlorophylls to the 2PE signals in the main plant light-harvesting complex (LHCII). For 2PE, excitation at 1210 and 1300 nm was used, being within the known 2PE profile of LHCII. At both excitation wavelengths, the transient absorption spectra exhibit a shape characteristic of excited chlorophylls with only a minor contribution from carotenoids. We compare the 2PE data measured for LHCII with those obtained from 2PE of a lutein/chlorophyll mixture in acetone. We estimate that although the 2PE cross section of a single carotenoid in acetone is ∼1.7 times larger than that of a Chl , due to the 1:3.5 carotenoid/Chl ratio in LHCII, only one-third of the absorbed 2PE photons excite carotenoids in LHCII in the 1200-1300 nm range.
飞秒瞬态吸收光谱法（fs-TAS）可用于确定类胡萝卜素和叶绿素在主植物光捕获复合物（LHCII）中的双光子激发（2PE）信号中的贡献。在 1210nm 和 1300nm 处进行 2PE 激发，这在 LHCII 的已知 2PE 谱内。在这两个激发波长处，瞬态吸收光谱呈现出与激发态叶绿素特征一致的形状，只有少量类胡萝卜素的贡献。我们将 LHCII 的 2PE 数据与从叶黄素/叶绿素混合物在丙酮中的 2PE 获得的数据进行了比较。我们估计，尽管单个类胡萝卜素在丙酮中的 2PE 截面比 Chl 大约 1.7 倍，但由于 LHCII 中的类胡萝卜素/Chl 比为 1:3.5，在 1200-1300nm 范围内，只有三分之一的吸收 2PE 光子激发 LHCII 中的类胡萝卜素。
