Activated OCP unlocks nonphotochemical quenching in cyanobacteria

Cogdell, R. J. and Gardiner, A. T. (2015) Activated OCP unlocks nonphotochemical quenching in cyanobacteria. Proceedings of the National Academy of Sciences of the United States of America, 112(41), pp. 12547-12548. (doi: 10.1073/pnas.1517477112) (PMID:26432879)

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Most aerobic photosynthetic organisms have enough light-harvesting capacity so that on bright sunny days their photosynthesis is saturated for the major part of the day (1, 2). Early on in such sunny days the capacity of the reaction centers to process the absorbed solar energy is exceeded. The excess absorbed photons are potentially very dangerous. For example, if the chlorophyll-excited singlet states created in the antenna complexes cannot be used productively by the reaction centers, then these singlet states can potentially last long enough to undergo intersystem crossing to produce triplets. Excited chlorophyll triplet states can interact with molecular oxygen to produce very dangerous products, such as singlet oxygen (3). Singlet oxygen is an extremely powerful oxidizing molecule that can irreversibly damage lipids and, indeed, most major biological polymers. Cells exposed to singlet oxygen are rapidly killed (4). Oxygenic phototrophs have evolved a process, called nonphotochemical quenching (NPQ), to mitigate this problem of overexcitation (5). These phototrophs are able to control the efficiency of their light-harvesting systems. Under nonsaturating incident light intensities, the antenna complexes work as efficient light-harvesters, transferring absorbed solar energy effectively to the reaction centers. As incident light intensities become saturating, the antenna complexes switch to a quenched state, where the lifetime of their excited singlet states are strongly reduced and the efficiency of energy transfer to the reaction centers is much lower. The excess absorbed light-energy is effectively detoxified and converted harmlessly into heat.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard and Gardiner, Dr Alastair
Authors: Cogdell, R. J., and Gardiner, A. T.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Proceedings of the National Academy of Sciences of the United States of America
Publisher:National Academy of Sciences
ISSN (Online):1091-6490

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