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J Am Chem Soc. 2016 Sep 14;138(36):11616-22. doi: 10.1021/jacs.6b04811. Epub 2016 Sep 2.

Controlling Light Harvesting with Light.

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Department of Physics and Astronomy, VU Amsterdam , 1081 HV Amsterdam, The Netherlands.
Department of Food Sciences, Faculty of Agriculture, Kagawa University , Miki-cho, Kagawa 761-0795, Japan.
Centre National de la Recherche Scientifique (CNRS), I2BC, UMR 9198 , 91191 Gif-sur-Yvette, France.
Commissariat à l'Energie Atomique (CEA), Institut de Biologie et Technologies de Saclay (iBiTec-S) , 91191 Gif-sur-Yvette, France.
Department of Physics, University of Pretoria , 0028 Hatfield, South Africa.


When exposed to intense sunlight, all organisms performing oxygenic photosynthesis implement various photoprotective strategies to prevent potentially lethal photodamage. The rapidly responding photoprotective mechanisms, occurring in the light-harvesting pigment-protein antennae, take effect within tens of seconds, while the dramatic and potentially harmful light intensity fluctuations manifest also on shorter time scales. Here we show that, upon illumination, individual phycobilisomes from Synechocystis PCC 6803, which, in vivo under low-light conditions, harvest solar energy, and have the built-in capacity to switch rapidly and reversibly into light-activated energy-dissipating states. Simultaneously measured fluorescence intensity, lifetime, and spectra, compared with a multicompartmental kinetic model, revealed that essentially any subunit of a phycobilisome can be quenched, and that the core complexes were targeted most frequently. Our results provide the first evidence for fluorescence blinking from a biologically active system at physiological light intensities and suggest that the light-controlled switches to intrinsically available energy-dissipating states are responsible for a novel type of photoprotection in cyanobacteria. We anticipate other photosynthetic organisms to employ similar strategies to respond instantly to rapid solar light intensity fluctuations. A detailed understanding of the photophysics of photosynthetic antenna complexes is of great interest for bioinspired solar energy technologies.


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