Structure and Function of Carotenoids

描述(申请人提供)：本申请中包含的研究目的是阐明类胡萝卜素的结构特征如何决定其在体内的光化学性质和生物学功能。将特别关注类胡萝卜素在捕光和光保护中的作用，这对光合作用生物的生存是必不可少的。要研究的系统包括体外的类胡萝卜素和从不同种类的藻类和原核生物和紫色光合细菌中获得的色素/蛋白质复合体。这些系统将被使用，因为反应中心和由它们制备的含有天线类胡萝卜素的色素-蛋白质复合体可以通过定点突变进行纯化、色素重组、色素交换、结晶和遗传改变。X射线结晶学、核磁共振和共振拉曼光谱将被用作直接结构探针。类胡萝卜素的光化学行为的动力学和量子力学模型将使用稳态吸收、荧光、荧光激发、电子顺磁共振、双光子和超快-瞬时吸收光谱进行测试。这些实验将通过理论量子力学计算得到加强，以实现结构与光谱可观测性和生物功能的定量关联。这项建议的具体目的是：(1)研究光合色素-蛋白质复合体中类胡萝卜素的结构；(2)探索类胡萝卜素结构与其光谱性质之间的关系；以及(3)确定类胡萝卜素结构与其在体内发挥作用的机制之间的关系。我们已经进行了几项初步研究，以支持我们建议采用的方法。

DESCRIPTION (provided by applicant): The objective of the research contained in this application is to elucidate how the structural features of carotenoids determine their photochemical properties and biological functions in vivo. Particular attention will be given to the roles of carotenoids in light-harvesting and photo-protection, which are essential for the survival of photosynthetic organisms. The systems to be studied include carotenoids in vitro and in pigment/protein complexes, obtained from different species of algae and prokaryotic and purple photosynthetic bacteria. These systems will be used, because reaction centers, and antenna carotenoid-containing pigment-protein complexes prepared from them, can be purified, pigment-reconstituted, pigment-exchanged, crystallized, and genetically altered via site-directed mutagenesis. X-ray crystallography, nuclear magnetic resonance, and resonance Raman spectroscopy will be used as direct structural probes. Kinetic and quantum mechanical models of the photochemical behavior of carotenoids will be tested using steady state absorption, fluorescence, fluorescence excitation, electron paramagnetic resonance, two-photon, and ultrafast-transient absorption spectroscopy. These experiments will be augmented by theoretical quantum mechanical computations, to allow a quantitative correlation of structure with spectroscopic observables and biological function. The specific aims of this proposal are: (1) To examine the structures of carotenoids in photosynthetic pigment-protein complexes; (2) To explore the relationships between the carotenoid structures and their spectroscopic properties; and (3) To determine the relationships between the carotenoid structures and the mechanisms by which they function in vivo. Several preliminary studies have already been carried out by us in support of the methods we propose to employ.