Time-Resolved ESR and ENDOR on Triplet States in Photosynthetic Antenna Complexes

光合天线复合体三重态的时间分辨 ESR 和 ENDOR

• 批准号: 9983034
• 负责人: Alexander Angerhofer
• 金额: $ 43万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-15 至 2004-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9983034&HistoricalAwards=false
• 关键词: Time; Resolved; ESR; ENDOR; Triplet

Angerhofer, AlexanderMCB-9983034Carotenoids are used in photosynthetic organisms to protect against the harmful photoinitiated sensitization of singlet oxygen by chlorophyll triplet states. The photoprotection mechanism of the carotenoids will be studied in bacterial, algal and higher plant photosynthetic antenna complexes using time-resolved ESR, ENDOR, and transient absorption techniques. The isotropic and anisotropic hyperfine interaction between the triplet electron spin and the carotenoid polyene chain protons will be analyzed by the time-resolved ENDOR. This will lead to the assignment of the triplet-carrying pigments and the determination of their electronic structures. The results of this research will lead to refinements of currently available X-ray structural data and/or the determination of structural changes that may occur in the excited triplet states. A detailed understanding of the temperature dependence of the triplet spin dynamics will be obtained by time-resolved ESR and will allow us to distinguish the different mechanisms of triplet energy transfer that take place in various antenna and reaction center complexes.Carotenoids are essential for the survival of photosynthetic organisms (plants, algae, and some bacteria). They serve an important protective role that allows the organism to get rid of excess energy without stimulating the production of singlet oxygen which is highly toxic. The process involves a transfer of a so-called triplet state from the chlorophylls to the carotenoids. This transfer of energy has so far been understood only in general terms and in many cases the identification of the actual pigments responsible for it is lacking. Furthermore, the details of the dynamic interaction between the triplet excited carotenoids or chlorophylls and their environment are not well understood. This work will fill this gap. This project is supported by the Molecular Biophysics Program in the Division of Molecular and Cellular Biosciences in the Directorate for Biological Sciences and the Physical Chemistry Program in the Division of Chemistry in the Mathematical and Physical Sciences Directorate.

Angerhofer，AlexandermCB-9983034甲状腺类固醇用于光合生物体，以防止叶绿素三重态对单线氧的有害光敏化的敏感性。类胡萝卜素的光保护机制将在细菌，藻类和较高的植物光合作用天线复合物中进行研究，并使用时间分辨的ESR，Endor和瞬时吸收技术进行研究。三胞胎电子自旋与类胡萝卜素多烯链质子之间的各向同性和各向异性超精细相互作用将由时间分辨的Endor分析。这将导致分配三胞胎颜料及其电子结构的测定。这项研究的结果将导致当前可用的X射线结构数据和/或确定激发三胞胎状态下可能发生的结构变化。对三胞胎自旋动力学温度依赖性的详细理解将通过时间分辨的ESR获得，并使我们能够区分在各种天线和反应中心配合物中发生的三胞胎能量转移的不同机制。类羟基型对于光合生物（植物，藻类和某些细菌）的存活至关重要。它们发挥着重要的保护作用，使生物体可以消除多余的能量，而无需刺激剧毒剧毒的单线氧的产生。该过程涉及将所谓的三重态从叶绿素转移到类胡萝卜素。到目前为止，这种能源的转移仅在一般情况下才被理解，在许多情况下，缺乏对其负责的实际色素的识别。此外，三胞胎激发类胡萝卜素或叶绿素及其环境之间动态相互作用的细节尚不清楚。这项工作将填补这一空白。该项目得到了分子生物物理学计划在分子和细胞生物科学局的生物科学局和数学和物理科学局化学划分的物理化学计划中的分子和细胞生物科学划分的支持。