Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 412477
Title Site, rate and mechanism of photoprotective quenching in cyanobacteria
Author(s) Tian, L.; Stokkum, I.H.M. van; Koehorst, R.B.M.; Jongerius, A.; Kirilovsky, D.; Amerongen, H. van
Source Journal of the American Chemical Society 133 (2011)45. - ISSN 0002-7863 - p. 18304 - 18311.
Department(s) Biophysics
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) orange carotenoid protein - light-harvesting complex - bacteriochlorophyll energy-transfer - synechocystis sp pcc-6803 - photosystem-ii - pcc 6803 - purple bacteria - s-1 state - phycobilisome fluorescence - 2-photon excitation
Abstract In cyanobacteria, activation of the Orange Carotenoid Protein (OCP) by intense blue-green light triggers photoprotective thermal dissipation of excess absorbed energy leading to a decrease (quenching) of fluorescence of the light harvesting phycobilisomes and, concomitantly, of the energy arriving to the reaction centers. Using spectrally resolved picosecond fluorescence, we have studied cells of wild-type Synechocystis sp. PCC 6803 and of mutants without and with extra OCP (¿OCP and OverOCP) both in the unquenched and quenched state. With the use of target analysis, we managed to spectrally resolve seven different pigment pools in the phycobilisomes and photosystems I and II, and to determine the rates of excitation energy transfer between them. In addition, the fraction of quenched phycobilisomes and the rates of charge separation and quenching were resolved. Under our illumination conditions, 72% of the phycobilisomes in OverOCP appeared to be substantially quenched. For wild-type cells, this number was only 29%. It is revealed that upon OCP activation, a bilin chromophore in the core of the phycobilisome, here called APCQ660, with fluorescence maximum at 660 nm becomes an effective quencher that prevents more than 80% of the excitations in the phycobilisome to reach Photosystems I and II. The quenching rate of its excited state is extremely fast, that is, at least (240 ± 60 fs)-1. It is concluded that the quenching is most likely caused by charge transfer between APCQ660 and the OCP carotenoid hECN in its activated form
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