A simple artificial light-harvesting dyad as a model for excess energy dissipation in oxygenic photosynthesis

Rudi Berera, Christian Herrero, Ivo H M Van Stokkum, Mikas Vengris, Gerdenis Kodis, Rodrigo E. Palacios, Herbert Van Amerongen, Rienk Van Grondelle, Devens Gust, Thomas Moore, Ana Moore, John T M Kennis

Research output: Contribution to journalArticlepeer-review

119 Scopus citations


Under excess illumination, plant photosystem II dissipates excess energy through the quenching of chlorophyll fluorescence, a process known as nonphotochemical quenching. Activation of non-photochemical quenching has been linked to the conversion of a carotenoid with a conjugation length of nine double bonds (violaxanthin) into an 11-double-bond carotenoid (zeaxanthin). It has been suggested that the increase in the conjugation length turns the carotenoid from a nonquencher into a quencher of chlorophyll singlet excited states, but unequivocal evidence is lacking. Here, we present a transient absorption spectroscopic study on a model system made up of a zinc phthalocyanine (Pc) molecule covalently linked to carotenoids with 9, 10, or 11 conjugated carbon-carbon double bonds. We show that a carotenoid can act as an acceptor of Pc excitation energy, thereby shortening its singlet excited-state lifetime. The conjugation length of the carotenoid is critical to the quenching process. Remarkably, the addition of only one double bond can turn the carotenoid from a nonquencher into a very strong quencher. By studying the solvent polarity dependence of the quenching using target analysis of the time-resolved data, we show that the quenching proceeds through energy transfer from the excited Pc to the optically forbidden S1 state of the carotenoid, coupled to an intramolecular charge-transfer state. The mechanism for excess energy dissipation in photosystem II is discussed in view of the insights obtained on this simple model system.

Original languageEnglish (US)
Pages (from-to)5343-5348
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number14
StatePublished - Apr 4 2006


  • Artificial photosynthesis
  • Carotenoid
  • Nonphotochemical quenching
  • Photoprotection
  • Xanthophyll cycle

ASJC Scopus subject areas

  • General


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