Photoprotection through ultrafast charge recombination in photochemical reaction centres under oxidizing conditions

Fei Ma, David J K Swainsbury, Michael R Jones, Rienk van Grondelle

Research output: Contribution to journalArticle (Academic Journal)peer-review

4 Citations (Scopus)
242 Downloads (Pure)

Abstract

Engineering natural photosynthesis to address predicted shortfalls in food and energy supply requires a detailed understanding of its molecular basis and the intrinsic photoprotective mechanisms that operate under fluctuating environmental conditions. Long-lived triplet or singlet excited electronic states have the potential to cause photodamage, particularly in the presence of oxygen, and so a variety of mechanisms exist to prevent formation of such states or safely dissipate their energy. Here, we report a dramatic difference in spectral evolution in fully reduced and partially oxidized Rhodobacter sphaeroides reaction centres (RCs) following excitation of the monomeric bacteriochlorophyll (BChl) cofactors at 805 nm. Three types of preparation were studied, including RCs purified as protein/lipid nanodiscs using the copolymer styrene maleic acid. In fully reduced RCs such excitation produces membrane-spanning charge separation. In preparations of partially oxidized RCs the spectroscopic signature of this charge separation is replaced by that of an energy dissipation process, including in the majority sub-population of reduced RCs. This process, which appears to take place on both cofactor branches, involves formation of a BChl+/bacteriopheophytin− radical pair that dissipates energy via recombination to a vibrationally hot ground state. The possible physiological role of this dissipative process under mildly oxidizing conditions is considered.
Original languageEnglish
Article number20160378
Number of pages8
JournalPhilosophical Transactions B: Biological Sciences
Volume372
Issue number1730
Early online date14 Aug 2017
DOIs
Publication statusPublished - Sep 2017

Keywords

  • reaction centre
  • photoprotection
  • charge recombination
  • ultrafast spectroscopy
  • styrene maleic acid

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