The Role of Xanthophylls in the Mechanism of Nonradiative Energy Dissipation in Photosynthesis

叶黄素在光合作用非辐射能量耗散机制中的作用

• 批准号: 9816759
• 负责人: Harry Frank
• 金额: $ 30.6万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-02-01 至 2003-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9816759&HistoricalAwards=false
• 关键词: Role; Xanthophylls; Mechanism; Nonradiative; Energy

Harry A. Frank9816759Photosynthetic organisms contain protective mechanisms by which excess light energy is dissipated before it leads to the photodestruction of the photosynthetic apparatus. Also, energy flow from the light-harvesting pigment-protein complexes to the photosynthetic reaction center is highly regulated. The molecular features that control these processes are not well understood. Xanthophyll pigments have been implicated in the mechanisms, but the precise nature of their involvement is unclear. In this project, several different xanthophylls will be studied. The experiments to be performed include steady state and time-resolved absorption and fluorescence spectroscopy and electrochemical determinations. The spectroscopic experiments will measure the efficiencies and dynamics of energy transfer between the xanthophylls and chlorophyll. The electrochemical experiments will reveal the oxidation potentials of the molecules in solution and bound in the pigment-protein complexes. The major objective of this research to examine each of the molecular factors thought to be important in nonradiative energy dissipation in order to reveal the detailed molecular mechanism by which it takes place in vivo. The factors to be explored include xanthophyll composition, state of aggregation, pH, phosphorylation, position of the energy levels, and the oxidation potentials of the pigments. The question of the involvement of the xanthophylls as direct or indirect quenchers of chlorophyll fluorescence will be examined. The hypotheses that xanthophylls quench chlorophyll fluorescence by energy transfer or electron transfer mechanisms will be tested. The experiments are important in enlarging our view of how photosynthetic organisms protect themselves from excessive light energy absorption and respond to varying environmental conditions while maintaining efficient energy flow essential for survival.Xanthophylls are familiar to anyone who has observed the bright orange and yellow colors of Autumn leaves in New England. However, unbeknownst to most observers, these eye-catching photosynthetic pigments do more than provide aesthetic beauty to our lives. They are critical components in a biological protection system that prevents chlorophyll, the most essential plant pigment, from breaking down under high light stress. In a way that is not yet fully understood, xanthophylls are able to be converted from one form into another and back again in the so-called "Xanthophyll cycle." The molecular components of this cycle appear to be capable of harmlessly deactivating excess excited state energy before it catalyzes the destruction of chlorophyll. Interestingly, the same components may also regulate the flow of absorbed solar energy between photosynthetic proteins. This research will investigate precisely how the protection and flow regulation are accomplished. Protein preparations from several higher plant and algal systems will be systematically investigated. A combination of biochemical, molecular biological, and spectroscopic tools will be used. The overall goal of the research is to elucidate the molecular details of how the Xanthophyll cycle works. A better understanding of how plants convert solar energy into chemical energy and withstand stress under bright solar conditions is expected to be obtained from this work.

Harry A. Frank9816759光合生物包含保护性机制，在导致光合作用仪的光电降低之前，通过该机制消散了过量的光能。同样，高度调节了从光收获色素蛋白复合物到光合反应中心的能量流。控制这些过程的分子特征尚不清楚。叶丁香颜料已经与机制有关，但其参与的确切性质尚不清楚。在这个项目中，将研究几种不同的黄叶斑。要进行的实验包括稳态和时间分辨的吸收以及荧光光谱和电化学测定。光谱实验将测量黄叶藻和叶绿素之间能量转移的效率和动力学。电化学实验将揭示溶液中分子的氧化电位，并结合在色素 - 蛋白质复合物中。这项研究的主要目的是检查每个分子因子在非赋值能耗散中很重要，以揭示其在体内发生的详细分子机制。要探索的因素包括叶蜜质组成，聚集状态，pH，磷酸化，能级的位置以及颜料的氧化潜力。将研究Xanthophylls作为叶绿素荧光的直接或间接淬灭剂的问题。将测试通过能量转移或电子转移机制释放叶绿素荧光的假设。这些实验对于扩大我们对光合生物如何保护自己免受过度光能吸收的看法至关重要，同时响应了不同的环境条件，同时保持了对生存必不可少的有效能量流。但是，对于大多数观察者而言，这些引人注目的光合色素的作用不仅仅是为我们的生活提供美学之美。它们是生物保护系统中的关键组成部分，该系统可防止叶绿素，最重要的植物色素，无法在高光应力下分解。从尚未完全理解的方式中，Xanthophylls可以在所谓的“ Xanthophyll循环”中从一种形式转化为另一种形式，然后再次转换为返回。该循环的分子成分似乎能够无害地停用过量的激发状态能量，然后才能催化叶绿素的破坏。有趣的是，相同的成分还可以调节光合蛋白之间吸收的太阳能的流动。这项研究将准确调查如何完成保护和流动调节。将系统研究来自几个高等植物和藻类系统的蛋白质制剂。将使用生化，分子生物学和光谱工具的组合。该研究的总体目标是阐明黄叶藻周期的工作方式的分子细节。对植物如何将太阳能转化为化学能并承受明亮的太阳条件下的应力有望从这项工作中获得更好的理解。