Ultrafast carotenoid to pheophorbide energy transfer in a biomimetic model for antenna function in photosynthesis

Michael R Wasielewski, Paul A. Liddell, Donna Barrett, Thomas A Moore, John Devens Gust

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Carotenoids serve as light-harvesting pigments and as photoprotective agents in photosynthetic organisms1-9. Their role as antenna pigments involves absorption of photons in the blue-green spectral region followed by highly efficient singlet-singlet energy transfer to a neighbouring chlorophyll. The dependence of both the rate and mechanism of energy transfer on carotenoid-chlorophyll distance and orientation is Unknown. Here, we have directly measured both the rate and efficiency of singlet energy transfer from a carotenoid covalently linked to pyropheophorbide a (PPheo a) in two model compounds, using picosecond transient absorption spectroscopy. In one model the π systems of the carotenoid and PPsheo a possess a maximum edge-to-edge distance of 5 Å, while in the other model this distance is only 2Å. Energy transfer occurs from the carotenoid to PPheo a at the 2-Å distance with a rate constant of 7 ± 2 × 1010 s-1 and 53±5% efficiency, while energy transfer at the 5-Å distance occurs at a rate constant of 9 s-1 and with

Original languageEnglish
Pages (from-to)570-572
Number of pages3
Issue number6079
Publication statusPublished - 1986


ASJC Scopus subject areas

  • General

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