Pigments Controlling the Quantum Efficiency of Photosynthetic Light Harvesting

控制光合作用光收集量子效率的颜料

• 批准号: EP/H024697/1
• 负责人: Alexander Ruban
• 金额: $ 38.95万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH024697%2F1
• 关键词: Pigments; Controlling; Quantum; Efficiency; Photosynthetic

The biological process of photosynthesis is the foundation upon which all life on Earth is supported. Since the advent of oxygenic photosynthesis, oxygen-evolving organisms have provided all heterotrophic organisms with both food and the oxygen required to utilize it. More recently, photosynthetic organisms have provided humans with a huge variety of useful compounds, including fuels, pharmaceuticals, fibres, pigments, and animal feeds and it has become apparent that plant-derived commodities will only increase in importance in the future green economy. The proliferation of oxygenic photosynthesis on Earth may be attributed to the efficient evolutionary design of the molecular machinery of photosynthesis, along with their adaptability with respect to changing environmental conditions. The photosynthetic membranes of the chloroplasts, commonly known as the thylakoid membranes, are the most complex of all biological membranes, being greatly enriched in a diverse collection of various protein complexes. These protein complexes represent the necessary molecular machinery of complex, multi-step process of photosynthesis, carrying out such diverse tasks as light-harvesting, electron transport and the synthesis of vital biochemical compounds. In order to fulfil these roles the various membrane proteins bind a number of cofactors such as chlorophylls, carotenoids, lipids, water, and various metal ions. One of the major pigment-lipoprotein complexes found within the thylakoid membrane is the light-harvesting complex of photosystem-II, LHCII. This complex, which is a trimer of three identical proteins, each binding 18 photosynthetic pigment molecules, collects light energy received by the thylakoid membrane and transfers it to the photosynthetic reaction centres. In addition to LHCII there are two minor light-harvesting complexes known as CP26 and CP29. In addition to this role LHCII, has been found to play an important role in regulating the amount of energy that is delivered to the reaction centre. This is achieved via the dissipation of excess energy absorbed during periods of intense illumination, a process commonly referred to as photoprotection. Recently we have discovered that the currently available structure of LHCII corresponds to the structure of a photoprotective conformation of the complex. This finding is of particular importance since it offers unique structural insights into how the thylakoid membrane senses and responds to excessive illumination, and hence how photosynthetic systems protect themselves against photodamage. It has also been suggested that the minor antennas, CP26 and CP29, rather than LHCII are responsible for photoprotection. The aim of this proposed work is to understand how the photosynthetic pigments known as xanthophylls regulate the amount of light energy delivered to the reactions centres by the major and minor antenna complexes. This work is divided into two copuled parts, each of which will employ a unique combination of methods from the fields of experimental biophysics, theoretical physics, and quantum chemistry to complete. First, it is essential to understand how varying the specific xanthophyll compliment of LHCII affects the rate of energy dissipation in the antenna complex. This will be achieved via spectroscopic measurements of the antenna complexes and theoretical modelling of the transfer of excitation energy. Second, we will investigate whether specific sites in LHCII, CP26, or CP29 are responsible for the dissipation of excess energy. This will require detailed theoretical modelling of the electronic properties of the photosynthetic pigments, theoretical simulation of the transfer and dissipation of energy within the antenna complexes, and detailed spectroscopic mapping of the energy transfer pathways within the antenna complexes of both mutants and natural specimens.

光合作用的生物过程是地球上所有生命赖以生存的基础。自产氧光合作用出现以来，氧进化生物为所有异养生物提供了食物和利用食物所需的氧气。最近，光合生物为人类提供了种类繁多的有用化合物，包括燃料、药品、纤维、色素和动物饲料。很明显，植物衍生的商品在未来的绿色经济中只会越来越重要。地球上含氧光合作用的扩散可能归因于光合作用分子机制的有效进化设计，以及它们对不断变化的环境条件的适应性。叶绿体的光合膜，通常被称为类囊体膜，是所有生物膜中最复杂的，富含各种各样的蛋白质复合物。这些蛋白质复合物代表了复杂的、多步骤的光合作用过程中必要的分子机制，执行诸如光收集、电子传递和重要生化化合物合成等各种任务。为了完成这些功能，各种膜蛋白结合了许多辅助因子，如叶绿素、类胡萝卜素、脂质、水和各种金属离子。在类囊体膜内发现的主要色素-脂蛋白复合物之一是光系统ii的光收集复合物，LHCII。这种复合体是由三种相同的蛋白质组成的三聚体，每种蛋白质结合18个光合色素分子，收集类囊体膜接收的光能，并将其转移到光合反应中心。除了LHCII，还有两种较小的光收集配合物CP26和CP29。除了这个作用，LHCII在调节传递到反应中心的能量方面也起着重要的作用。这是通过在强照明期间吸收的多余能量的耗散来实现的，这一过程通常被称为光保护。最近我们发现LHCII目前可用的结构对应于络合物的光保护构象的结构。这一发现特别重要，因为它为类囊体膜如何感知和响应过度照明以及光合系统如何保护自己免受光损伤提供了独特的结构见解。也有人提出，较小的天线，CP26和CP29，而不是LHCII负责光保护。这项拟议工作的目的是了解被称为叶黄素的光合色素如何调节通过主要和次要天线复合物传递到反应中心的光能的数量。本工作分为两部分，每一部分都将采用实验生物物理学、理论物理学和量子化学领域的独特组合方法来完成。首先，有必要了解改变LHCII的特定叶黄素补充如何影响天线复合体的能量耗散率。这将通过天线复合体的光谱测量和激发能转移的理论建模来实现。其次，我们将研究LHCII、CP26或CP29中的特定位点是否负责多余能量的耗散。这将需要对光合色素的电子特性进行详细的理论建模，对天线复合体内能量的转移和耗散进行理论模拟，并对突变体和自然样本的天线复合体内的能量转移途径进行详细的光谱映射。