LOCATION OF THE CAROTENOID 2Ag-STATE AND ITS ROLE IN PHOTOSYNTHESIS |
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| Authors: | T. Gillbro P. O. Andersson R. S. H. Liu A. E. Asato S. Takaishi R. J. Cogdell |
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| Affiliation: | Department of Physical Chemistry, University of Umeå, S-901 87 Umeå, Sweden;Department of Chemistry, 2545 The Mall, University of Hawaii, Honolulu, HI 96822, USA;Department of Botany, University of Glasgow, Glasgow G12 800, Scotland, UK |
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| Abstract: | The location of the carotenoid 2Ag-state (S1) was studied by fluorescence spectroscopy in two series of carotenoids. One consisted of natural polyenes like phytoene, phytofluene, β-carotene, and neurosporene, and the other of minicarotenes, i.e., compounds similar to β-carotene, but with a smaller number of double bonds (n=3–9). A decrease of the S1-S0 energy gap with n was observed in both series, and extrapolation to n= 11 gave the energies 14 500 and 13 200 cm?1 for β-carotene and lycopene, respectively. The neurosporene S1 state was located at ca 16 000 cm?1. A good relationship between the nonradiative relaxation rate and the number of conjugation was observed. The rate increased by a factor of 2.5 per double bond. The possible role of the S1 state in reversible carotenoid ← chlorophyll electron-exchange energy transfer is discussed. |
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