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DNA as UV light-harvesting antenna.

ABSTRACT: The ordered structure of UV chromophores in DNA resembles photosynthetic light-harvesting complexes in which quantum coherence effects play a major role in highly efficient directional energy transfer. The possible role of coherent excitons in energy transport in DNA remains debated. Meanwhile, energy transport properties are greatly important for understanding the mechanisms of photochemical reactions in cellular DNA and for DNA-based artificial nanostructures. Here, we studied energy transfer in DNA complexes formed with silver nanoclusters and with intercalating dye (acridine orange). Steady-state fluorescence measurements with two DNA templates (15-mer DNA duplex and calf thymus DNA) showed that excitation energy can be transferred to the clusters from 21 and 28 nucleobases, respectively. This differed from the DNA-acridine orange complex for which energy transfer took place from four neighboring bases only. Fluorescence up-conversion measurements showed that the energy transfer took place within 100 fs. The efficient energy transport in the Ag-DNA complexes suggests an excitonic mechanism for the transfer, such that the excitation is delocalized over at least four and seven stacked bases, respectively, in one strand of the duplexes stabilizing the clusters. This result demonstrates that the exciton delocalization length in some DNA structures may not be limited to just two bases.

SUBMITTER: Volkov IL

PROVIDER: S-EPMC6283424 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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DNA as UV light-harvesting antenna.

Volkov Ivan L IL Reveguk Zakhar V ZV Serdobintsev Pavel Yu PY Ramazanov Ruslan R RR Kononov Alexei I AI

Nucleic acids research 20180401 7

The ordered structure of UV chromophores in DNA resembles photosynthetic light-harvesting complexes in which quantum coherence effects play a major role in highly efficient directional energy transfer. The possible role of coherent excitons in energy transport in DNA remains debated. Meanwhile, energy transport properties are greatly important for understanding the mechanisms of photochemical reactions in cellular DNA and for DNA-based artificial nanostructures. Here, we studied energy transfer ...[more]

PMID: 29186575

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Project description:One of the major constraints limiting biomass production in autotrophs is the low thermodynamic efficiency of photosynthesis, ranging from 1 to 4%. Given the absorption spectrum of photosynthetic pigments and the spectral distribution of sunlight, photosynthetic efficiencies as high as 11% are possible. It is well-recognized that the greatest thermodynamic inefficiencies in photosynthesis are associated with light absorption and conversion of excited states into chemical energy. This is due to the fact that photosynthesis light saturates at one quarter full sunlight intensity in plants resulting in the dissipation of excess energy as heat, fluorescence and through the production of damaging reactive oxygen species. Recently, it has been demonstrated that it is possible to adjust the size of the light harvesting antenna over a broad range of optical cross sections through targeted reductions in chlorophyll b content, selectively resulting in reductions of the peripheral light harvesting antenna size, especially in the content of Lhcb3 and Lhcb6. We have examined the impact of alterations in light harvesting antenna size on the amplitude of photoprotective activity and the evolutionary fitness or seed production in Camelina grown at super-saturating and sub-saturating light intensities to gain an understanding of the driving forces that lead to the selection for light harvesting antenna sizes best fit for a range of light intensities. We demonstrate that plants having light harvesting antenna sizes engineered for the greatest photosynthetic efficiency also have the greatest capacity to mitigate high light stress through non-photochemical quenching and reduction of reactive oxygen associated damage. Under sub-saturating growth light intensities, we demonstrate that the optimal light harvesting antenna size for photosynthesis and seed production is larger than that for plants grown at super-saturating light intensities and is more similar to the antenna size of wild-type plants. These results suggest that the light harvesting antenna size of plants is designed to maximize fitness under low light conditions such as occurs in shaded environments and in light competition with other plants.

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DNA as UV light-harvesting antenna.

Publications

DNA as UV light-harvesting antenna.

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