Red chlorophyll excitation dynamics in Arthrospira platensis photosystem I trimeric complexes as studied by femtosecond transient absorption spectroscopy |
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Authors: | Viktor Kompanets Vladimir Shubin Irina Terekhova Elena Kotova Vladimir Kozlovsky Vladimir Novoderezhkin Sergey Chekalin Navasard Karapetyan Andrei Razjivin |
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Institution: | 1. A.N. Bach Institute of Biochemistry RAS, 119071 Moscow, Russia;2. Institute of Spectroscopy RAS, 142190 Troitsk, Moscow Region, Russia;3. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia |
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Abstract: | Femtosecond absorption spectroscopy was applied to study for the first time excitation dynamics in isolated photosystem I trimers from Arthrospira platensis, which display extremely long-wavelength absorption peaks. Pump–probe spectra observed at 77 K in the timescale of dozens of picoseconds upon 70-fs excitation revealed two maxima near 710 and 730 nm, which correspond to red chlorophyll forms. Bleaching at 680 nm developed in ∼200 fs, whereas the bleaching kinetics at 710 and 730 nm exhibited two components with time constants of 1 and 5.5 ps. Comparison of the kinetics of bleaching development at 710 nm and 730 nm with that of bleaching decay at 680 nm indicated that both long-wavelength forms of trimers are populated mainly via direct energy transfer from bulk chlorophyll. |
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Keywords: | Photosystem I trimer Long-wavelength red chlorophyll form Femtosecond pump&ndash probe spectroscopy Arthrospira platensis |
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