Nguyen Hoang Long, Do Thanh Nhut, Akhtar Parveen, Jansen Thomas L C, Knoester Jasper, Wang Wenda, Shen Jian-Ren, Lambrev Petar H, Tan Howe-Siang
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
University of Groningen, Zernike Institute for Advanced Materials, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
J Phys Chem B. 2021 Feb 4;125(4):1134-1143. doi: 10.1021/acs.jpcb.0c10634. Epub 2021 Jan 22.
is a marine green macroalga adapted to the intertidal environment. It possesses siphonaxanthin-binding light-harvesting complexes of photosystem II (LHCII) with spectroscopic properties markedly different from the LHCII in plants. By applying a phenomenological fitting procedure to the two-dimensional electronic spectra of the LHCII from measured at 77 K, we can extract information about the excitonic states and energy-transfer processes. The fitting method results in well-converged parameters, including excitonic energy levels with their respective transition dipole moments, spectral widths, energy-transfer rates, and coupling properties. The 2D spectra simulated from the fitted parameters concur very well with the experimental data, showing the robustness of the fitting method. An excitonic energy-transfer scheme can be constructed from the fitting parameters. It shows the rapid energy transfer from chlorophylls (Chls) to at subpicosecond time scales and a long-lived state in the Chl region at around 659 nm. Three weakly connected terminal states are resolved at 671, 675, and 677 nm. The lowest state is higher in energy than that in plant LHCII, which is probably because of the fewer number of Chls in a LHCII monomer. Modeling based on existing Hamiltonians for the plant LHCII structure with two Chls switched to Chls suggests several possible Chl - replacements in comparison with those of plant LHCII. The adaptive changes result in a slower energy equilibration in the complex, revealed by the longer relaxation times of several exciton states compared to those of plant LHCII. The strength of our phenomenological fitting method for obtaining excitonic energy levels and energy-transfer network is put to the test in systems such as LHCII, where prior knowledge on exact assignment and spatial locations of pigments are lacking.
是一种适应潮间带环境的海洋绿色大型藻类。它拥有与植物光系统II（LHCII）中光谱性质明显不同的结合虹吸叶黄素的捕光复合物。通过对在77K下测量的LHCII的二维电子光谱应用现象学拟合程序，我们可以提取有关激子态和能量转移过程的信息。该拟合方法得到了收敛良好的参数，包括激子能级及其各自的跃迁偶极矩、光谱宽度、能量转移速率和耦合特性。根据拟合参数模拟的二维光谱与实验数据非常吻合，表明了拟合方法的稳健性。可以从拟合参数构建激子能量转移方案。它显示了在亚皮秒时间尺度上从叶绿素（Chls）到的快速能量转移以及在约659nm的Chl区域中的长寿命状态。在671、675和677nm处解析出三个弱连接的终端态。最低态的能量高于植物LHCII中的最低态，这可能是因为LHCII单体中Chls的数量较少。基于现有的植物LHCII结构哈密顿量进行建模，将两个Chls替换为Chls，与植物LHCII相比，提出了几种可能的Chl - 替换。与植物LHCII相比，几种激子态的弛豫时间更长，这表明这些适应性变化导致复合物中的能量平衡变慢。我们用于获得激子能级和能量转移网络的现象学拟合方法的优势在诸如LHCII等系统中得到了检验，在这些系统中缺乏关于色素的确切归属和空间位置的先验知识。
