Slow exciton trapping in Photosystem II: A possible physiological role |
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Authors: | Robert C Jennings Flavio M Garlaschi Laura Finzi Giuseppe Zucchelli |
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Institution: | (1) Centro CNR sulla Biologia Cellulare e Molecolare delle Piante, Dipartimento di Biologia, Università di Milano, via Celoria 26, 20133 Milano, Italy |
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Abstract: | Photosystem II, which has a primary photochemical charge separation time of about 300 ps, is the slowest trapping of all photosystems. On the basis of an analysis of data from the literature this is shown to be due to a number of partly independent factors: a shallow energy funnel in the antenna, an energetically shallow trap, exciton dynamics which are partly trap limited and a large antenna. It is argued that the first three of these properties of Photosystem II can be understood in terms of protective mechanisms against photoinhibition. These protective mechanisms, based on the generation of non photochemical quenching states mostly in the peripheral antenna, are able to decrease pheophytin reduction under conditions in which the primary quinone, QA, is already reduced, due to the slow trapping properties. The shallow antenna funnel is important in allowing quenching state-protective mechanisms in the peripheral antenna.Abbreviations chl
chlorophyll
- PS I
Photosystem I
- PS II
Photosystem II
- QA
the primary quinone acceptor
- RC
reaction centre
- RT
room temperature |
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Keywords: | antenna-trap equilibration photoinhibition photoprotection Photosystem II trapping time |
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