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Scientific result | Photosynthesis | Solar energy
Researchers from SB2SM and four other Research Teams (Yale University, Arizona State University, Argonne National Lab and Institute for High Performance Computing, Singapore) have identified a photosynthesis mechanism that protects plants from excess light energy . These results could contribute to the development of more efficient energy systems in new solar technologies.
In photosynthetic organisms, protection against photooxidative stress due to singlet oxygen is provided by carotenoid molecules, which quench chlorophyll triplet species before they can sensitize singlet oxygen formation. In anoxygenic photosynthetic organisms, in which exposure to oxygen is low, chlorophyll-to-carotenoid triplet–triplet energy transfer (T-TET) is slow, in the tens of nanoseconds range, whereas it is ultrafast in the oxygen-rich chloroplasts of oxygen-evolving photosynthetic organisms. To better understand the structural features and resulting electronic coupling that leads to T-TET dynamics adapted to ambient oxygen activity, we have carried out experimental and theoretical studies of two isomeric carotenoporphyrin molecular dyads having different conformations and therefore different interchromophore electronic interactions. This pair of dyads reproduces the characteristics of fast and slow T-TET, including a resonance Raman-based spectroscopic marker of strong electronic coupling and fast T-TET that has been observed in photosynthesis. As identified by density functional theory (DFT) calculations, the spectroscopic marker associated with fast T-TET is due primarily to a geometrical perturbation of the carotenoid backbone in the triplet state induced by the interchromophore interaction. This is also the case for the natural systems, as demonstrated by the hybrid quantum mechanics/molecular mechanics (QM/MM) simulations of light-harvesting proteins from oxygenic (LHCII) and anoxygenic organisms (LH2). Both DFT and electron paramagnetic resonance (EPR) analyses further indicate that, upon T-TET, the triplet wave function is localized on the carotenoid in both dyads.Read the French version.
Ho J, Kish E, Méndez-Hernández DD, WongCarter K, Pillai S,
Kodis G, Niklas J, Poluektov OG, Gust D, Moore TA, Moore AL, Batista VS, Robert B. Triplet–triplet energy transfer in artificial and natural photosynthetic antennas. (2017) Proc.Natl.Acad.Sci., http://dx.doi.org/10.1073/pnas.1614857114
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