Natural and Artificial Chlorosomal Light-Harvesting Antenna: Relationship between the Supramolecular Organisation and the Properties of the Electronic Excitations.

天然和人造染色体光捕获天线：超分子组织与电子激发特性之间的关系。

• 批准号: 256462505
• 负责人: Professor Dr. Jürgen Köhler
• 金额: --
• 依托单位: Institut für Organische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/256462505?language=en
• 关键词: Natural; Artificial; Chlorosomal; Light; Harvesting

The success of photosynthesis has inspired many researchers to study organic matter for solar energy conversion. However, a simple order-of-magnitude estimate reveals that under optimum conditions a typical organic molecule would absorb only a few photons per second. Hence, employing organic matter for any kind of solar driven energy production requires an efficient light-harvesting apparatus - an antenna - for collecting as many photons as possible. One of the most efficient antenna systems found in nature is that of the green-sulphur bacteria, which thrive photosynthetically under extremely low illumination conditions. There the light is absorbed in supramolecular arrangements of bacteriochlorophyll molecules that are referred to as chlorosomes. Unfortunately, chlorosomes feature a large degree of structural variability, which has hampered to resolve the structure of these assemblies with atomic resolution to date. In order to reduce the sample heterogeneity researchers either developed mutants with better controlled pigment content, or synthesized chemically well-defined model systems that structurally resemble their natural counterparts. Though, the structure of the chlorosomes is still a matter of an ongoing debate.Owing to the intermolecular interactions between the monomers, the lowest electronically excited states of such molecular assemblies are described as Frenkel excitons, which correspond to delocalised excitations that are coherently shared by many molecules. Since the photophysical properties of such exciton states depend crucially on the mutual arrangement of the pigments, information about the supramolecular organisation can be accessed also by optical spectroscopy. However, the great heterogeneity of the samples leads to inhomogeneous broadening of the spectra and subtle features, that might be charateristic for specific structural properties, are masked due to ensemble averaging.Aim of this project is a systematic study of natural (wild type and mutants) as well as artificial chlorosomes by single-molecule spectroscopic techniques. This includes absorption, fluorescence-excitation, and emission spectroscopy as well as the development of circular dichroism spectroscopy on an individual object. This approach will minimize the ensemble heterogeneity and provide information about the spectral positions of the exciton transitions, the relative intensity ratios of the exciton transitions, the mutual orientation of their transition-dipole moments, and the chirality of the pigment arrangement. In parallel, the experimental results will be compared with the predictions from computer simulations that will be conducted as a function of the geometrical arrangement of the monomers. Our goal is to discriminate between the various structural models discussed in the literature and to find out whether there is a systematic variation of the morphology of the chlorosomes as a function of the pigment composition.

光合作用的成功激发了许多研究人员研究太阳能转化的有机物。但是，简单的含量顺序估算表明，在最佳条件下，典型的有机分子每秒只能吸收几个光子。因此，在任何类型的太阳能驱动能源生产中使用有机物都需要有效的轻度收获设备（一种天线），以收集尽可能多的光子。自然界中发现的最有效的天线系统之一是绿硫细菌，在极低的照明条件下，光合体现了光合作用。那里的光在被称为氯化体的细菌氯叶叶分子的超分子排列中吸收。不幸的是，氯化体具有很大程度的结构可变性，迄今为止，它已阻碍了以原子分辨率解​​决这些组件的结构。为了减少样品异质性，研究人员要么开发了具有更好控制色素含量的突变体，要么合成化学定义明确的模型系统，它们在结构上类似于其自然对应物。但是，氯化体的结构仍然是一个正在进行的辩论的问题。由于单体之间的分子间相互作用，这种分子组件的最低电子激发态被描述为Frenkel Ickitons，这与许多分子共享的分离性激励相对应。由于这种激子状态的光物理特性至关重要地取决于颜料的相互排列，因此也可以通过光学光谱访问有关超分子组织的信息。然而，样品的极大异质性导致光谱和微妙特征的不均匀宽扩大，这可能是特定结构特性的特定特性，由于整体平均而被遮盖。这包括吸收，荧光激发和发射光谱以及在单个物体上的圆二色性光谱的发展。这种方法将使集成异质性最小化，并提供有关激子跃迁的光谱位置，激子跃迁的相对强度比，其过渡 - 偶极力矩的相互取向以及色素排列的chirality的信息。同时，将将实验结果与计算机模拟的预测进行比较，这些预测将是单体几何布置的函数。我们的目标是区分文献中讨论的各种结构模型，并找出叶绿体形态是否存在系统变化，这是色素组成的函数。

项目成果

Spectral and Structural Variations of Biomimetic Light-Harvesting Nanotubes.

仿生光捕获纳米管的光谱和结构变化

• DOI: 10.1021/acs.jpclett.9b00303
• 发表时间: 2019
• 期刊: The journal of physical chemistry letters
• 作者: A. Löhner;T. Kunsel;M. I. S. Röhr;T. L. C. Jansen;S. Sengupta;F. Würthner;J. Knoester;J. Köhler
• 通讯作者: J. Köhler