Photoprotective mechanisms in the core LH1 antenna pigment-protein complex from the purple photosynthetic bacterium, Rhodospirillum rubrum

Chiasa Uragami, Hiroki Sato, Nao Yukihira, Masazumi Fujiwara, Daisuke Kosumi, Alastair T. Gardiner, Richard J. Cogdell, Hideki Hashimoto

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Time-resolved absorption spectra from the femtoscecond to sub-millisecond time regimes were recorded in order to eluciate the photoprotective mechanisms of carotenoid (spirilloxanthin) in core LH1 light-harvesting pigment-protein complexes from a purple photosynthetic bacterium, Rhodospirillum (Rsp.) rubrum. Carotenoids can prevent the production of singlet oxygen by rapidly quenching the Bchl a triplet state. Through this triplet-triplet energy-transfer reaction the carotenoid is believed to protect the biological system from exposure to excess light. We set out to investigate this paricular function in the purple bacterium, Rsp. rubrum strain S1. We also investigated Rsp. rubrum strain G9+, which is the carotenoidless mutant of Rsp. rubrum, to make sure that the carotenoid is truly playing this important role. As a result, we could demonstrate that strain S1 realizes nearly 100% excitation energy transfer from triplet Bchl a to carotenoid. In addition, we found another major excited state deactivation channel of carotenoids, which takes away excess energy directly from the singlet excited state of Bchl a and so prevents the production of triplet excited Bchl a.

Original languageEnglish
Article number112628
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume400
DOIs
Publication statusPublished - Sep 1 2020
Externally publishedYes

Keywords

  • Carotenoid
  • LH1 pigment-protein antenna complex
  • Photoprotective function
  • Purple photosynthetic bacteria
  • Time-resolved absorption spectroscopy

ASJC Scopus subject areas

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

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