Triplet Delocalization over the Reaction Center Chlorophylls in Photosystem II

Taichi Hayase, Yuichiro Shimada, Tatsuya Mitomi, Ryo Nagao, Takumi Noguchi

Research output: Contribution to journalArticlepeer-review


The triplet state of chlorophyll formed by charge recombination in photosystem II (PSII) is a precursor of harmful singlet oxygen. Although main localization of the triplet state on the monomeric chlorophyll, ChlD1, at cryogenic temperatures has been suggested, how the triplet state is delocalized on other chlorophylls remains unclear. Here, we investigated the distribution of the triplet state of chlorophyll in PSII using light-induced Fourier transform infrared (FTIR) difference spectroscopy. Measurements of triplet-minus-singlet FTIR difference spectra with PSII core complexes from cyanobacterial mutants, D1-V157H, D2-V156H, D2-H197A, and D1-H198A, in which the interactions of the 131-keto C═O groups of the reaction center chlorophylls, PD1, PD2, ChlD1, and ChlD2, respectively, were perturbed, identified the 131-keto C═O bands of the individual chlorophylls and showed that the triplet state is delocalized over all of these chlorophylls. It is suggested that the triplet delocalization plays important roles in the photoprotection and photodamage mechanisms in PSII.

Original languageEnglish
JournalJournal of Physical Chemistry B
Publication statusAccepted/In press - 2023

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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