Carotenoid triplet detection by time-resolved EPR spectroscopy in carotenopyropheophorbide dyads

Donatella Carbonera, Marilena Di Valentin, Carlo Corvaja, Giovanni Giacometti, Giancarlo Agostini, Paul A. Liddell, Ana L. Moore, Thomas A. Moore, Devens Gust

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Carotenoid triplets play a photoprotective role in natural photosynthesis. The main process of carotenoid triplet formation is known to be triplet-triplet energy transfer from chlorophyll triplets. The structural requirements for high transfer yields are still a matter of discussion and the presence of competitive triplet formation pathways has not been excluded. Transient EPR measurements of triplet states formed by photoexcitation allow detection of the initial spin polarization. This pattern derives from the mechanism of triplet formation. In the case of triplet-triplet energy transfer, if the condition of spin angular momentum conservation is fulfilled, simulation of the EPR spectra gives information about the donor-acceptor mutual orientation. We describe transient EPR experiments on two artificial photosynthetic dyads, consisting of a carotenoid covalently-linked to a free-base or zinc substituted pyropheophorbide moiety and we discuss the results in terms of possible dyad conformations.

Original languageEnglish
Pages (from-to)329-335
Number of pages7
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume105
Issue number2-3
DOIs
Publication statusPublished - May 30 1997

Keywords

  • Carotenoids
  • Dyads
  • Porphyrins
  • TREPR
  • Triplets

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Physics and Astronomy(all)

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