Mapping the excitation energy migration pathways in phycobilisomes from the cyanobacterium Acaryochloris marina |
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Authors: | Dariusz M Niedzwiedzki Shira Bar-Zvi Robert E Blankenship Noam Adir |
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Institution: | 1. Department of Energy, Environmental & Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA;2. Center for Solar Energy and Energy Storage, Washington University in St. Louis, St. Louis, MO 63130, USA;3. Photosynthetic Antenna Research Center, Washington University in St. Louis, St. Louis, MO 63130, USA;4. Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel;5. Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA;6. Departments of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA |
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Abstract: | In this study, we use ultrafast time-resolved absorption and fluorescence spectroscopies to examine A. marina phycobilisomes isolated from cells grown under light of different intensities and spectral regimes. Investigations were performed at room temperature and at 77?K. The study demonstrates that if complexes are stabilized by high phosphate (900?mM) buffer, there are no differences between them in temporal and spectral properties of fluorescence. However, when the complexes are allowed to disassemble into trimers in low phosphate (50?mM) buffer, differences are clearly observed. The fluorescence properties of intact or disassembled phycobilisomes from cells grown in low intensity white light are unresponsive to variation in phosphate concentration. This antenna complex was further studied in detail with application of femtosecond time-resolved absorption at room temperature. Combined spectroscopic and kinetic analysis of time-resolved fluorescence and absorption data of this antenna allowed us to identify spectrally different forms of phycocyanobilins and to propose a simplified model of how they could be distributed within the phycobilisome structure. |
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Keywords: | Corresponding author at: Department of Energy Environmental & Chemical Engineering and Center for Solar Energy and Energy Storage Washington University in St Louis St Louis MO 63130 Campus Box 1180 USA |
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