Molecular factors controlling photosynthetic light harvesting by carotenoids.
Molecular factors controlling photosynthetic light harvesting by carotenoids.
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DOI：
10.1021/ar100030m
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发表时间：
2010-08-17
影响因子：
18.3
通讯作者：
Frank, Harry A.
中科院分区：
文献类型：
--
作者：
Polivka, Tomas;Frank, Harry A.
类胡萝卜素是一种自然产生的色素，它能吸收太阳光照射范围最大的光谱区域内的光。这些分子将这些能量传递给叶绿素，启动光合作用的主要光化学事件。类胡萝卜素还能调节光合器官内的能量流动，并保护其免受因过度吸收光而引起的光致损伤。为了在自然界中实现这些功能，类胡萝卜素结合在靠近叶绿素的离散色素蛋白复合物中。这些类胡萝卜素复合物的一些三维结构已被x射线晶体学确定。因此，为尝试将结构信息与类胡萝卜素的光谱特性联系起来，以了解其在光合系统中功能的分子机制奠定了基础。在这篇文章中，我们总结了纯化的类胡萝卜素在紫色细菌、海藻和绿色植物的溶液中和结合在光收集配合物中的激发态能和超快动力学的光谱数据。许多这些复合物可以通过诱变或色素交换进行修饰，从而促进结构和功能之间的相关性。我们描述了控制类胡萝卜素作为能量供体功能的结构和电子因素。我们还讨论了与光谱暗激发态性质有关的未解决的问题，这可能在光收集中发挥作用。为了说明结构确定和光谱研究之间的相互作用，我们描述了四种光收集配合物的光谱特性，其结构已确定为原子分辨率。第一种，来自紫色细菌嗜酸红假单胞菌的LH2复合物，含有类胡萝卜素，红紫红质葡萄糖苷。第二种是来自高等植物的LHCII三聚体复合物，它利用类胡萝卜素、叶黄素、新黄质和紫黄质将能量传递给叶绿素。第三种，来自甲藻的橄榄素-叶绿素-蛋白（PCP），是唯一已知的结合类胡萝卜素（橄榄素）色素数量超过叶绿素的复合体。最后一种是来自真细菌，即橡胶盐杆菌的黄嘌呤。这种复合物含有类胡萝卜素，盐黄质，它将能量传递给视网膜发色团。这些色素-蛋白质复合物中的类胡萝卜素通过优化类胡萝卜素供体和叶绿素受体分子的距离和取向，高效地传递能量。重要的是，类胡萝卜素在这些光收集色素-蛋白质复合物中的多功能性和坚固性导致它们被纳入纳米级天线系统的设计和合成中。在这些以生物为灵感的系统中，研究人员正在寻求改进光捕获和利用太阳发射光谱中的能量。
Carotenoids are naturally-occurring pigments that absorb light in the spectral region in which the sun irradiates maximally. These molecules transfer this energy to chlorophylls, initiating the primary photochemical events of photosynthesis. Carotenoids also regulate the flow of energy within the photosynthetic apparatus and protect it from photo-induced damage caused by excess light absorption. To carry out these functions in nature, carotenoids are bound in discrete pigment-protein complexes in close proximity to chlorophylls. A few 3D structures of these carotenoid complexes have been determined by X-ray crystallography. Thus, the stage is set for attempting to correlate the structural information with the spectroscopic properties of carotenoids to understand the molecular mechanism(s) of their function in photosynthetic systems. In this Account, we summarize current spectroscopic data describing the excited state energies and ultrafast dynamics of purified carotenoids in solution and bound in light-harvesting complexes from purple bacteria, marine algae, and green plants. Many of these complexes can be modified using mutagenesis or pigment exchange which facilitates making the correlations between structure and function. We describe the structural and electronic factors controlling the function of carotenoids as energy donors. We also discuss unresolved issues related to the nature of spectroscopically dark excited states, which could play a role in light-harvesting. To illustrate the interplay between structural determinations and spectroscopic investigations that exemplifies work in the field, we describe the spectroscopic properties of four light-harvesting complexes whose structures have been determined to atomic resolution. The first, the LH2 complex from the purple bacterium Rhodopseudomonas acidophila, contains the carotenoid, rhodopin glucoside. The second is the LHCII trimeric complex from higher plants which uses the carotenoids, lutein, neoxanthin and violaxanthin to transfer energy to chlorophyll. The third, the peridinin-chlorophyll-protein (PCP) from the dinoflagellate, Amphidinium carterae, is the only known complex where the bound carotenoid (peridinin) pigments outnumber the chlorophylls. The last is xanthorhodopsin from the eubacterium, Salinibacter ruber. This complex contains the carotenoid, salinixanthin, which transfers energy to a retinal chromophore. The carotenoids in these pigment-protein complexes transfer energy with high efficiency by optimizing both the distance and orientation of the carotenoid donor and chlorophyll acceptor molecules. Importantly, the versatility and robustness of carotenoids in these light-harvesting pigment-protein complexes have led to their incorporation in the design and synthesis of nanoscale antenna systems. In these bio-inspired systems, researchers are seeking to improve the light capture and use of energy from the solar emission spectrum.
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