Primary Processes in Fe-S-Type Photosynthetic Reaction Centers

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9418415 Blankenship Experiments are proposed to extend the current understanding of the energy trapping processes, primary photochemistry and early secondary electron transfer reactions in photosynthetic reaction centers that contain FeS centers as early electron acceptors. The particular systems that will be studied included reaction centers from the primitive anoxygenic organisms known as heliobacteria as well as Photosystem I of oxygenic photosynthetic organisms. Specific proposed experiments include low-temperature picosecond transient absorbance spectroscopic studies of energy transfer and trapping in both heliobacteria and Photosystem I, picosecond transient absorbance measurement in the blue spectral region in both systems, and investigation of secondary electron transfer reactions in heliobacteria monitored using EPR and millisecond timescale transient absorbance spectroscopy. These experiments will give new insights into the energy trapping process in reaction centers that contain integral core antenna pigments and will help to identify and characterize some of the early electron acceptors in these systems, including chlorophylls, quinones and FeS centers. %%% This project will increase our understanding of how plants and other photosynthetic organisms convert the energy of sunlight into chemical energy. The process of photosynthesis supplies all of our food and most of our energy needs. Many aspects of how photosynthesis works are not understood at a deep level. This project is designed to give detailed knowledge of the chemical mechanism of this essential biological process. ***