Energetics of Photosystem II charge recombination in Acaryochloris marina studied by thermoluminescence and flash-induced chlorophyll fluorescence measurements

Krisztián Cser, Zsuzsanna Deák, Alison Telfer, James Barber, Imre Vass

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19 Citations (Scopus)

Abstract

We studied the charge recombination characteristics of Photosystem II (PSII) redox components in whole cells of the chlorophyll (Chl) d-dominated cyanobacterium, Acaryochloris marina, by flash-induced chlorophyll fluorescence and thermoluminescence measurements. Flash-induced chlorophyll fluorescence decay was retarded in the μs and ms time ranges and accelerated in the s time range in Acaryochloris marina relative to that in the Chl a-containing cyanobacterium, Synechocystis PCC 6803. In the presence of 3-(3,4- dichlorophenyl)-1, 1-dimethylurea, which blocks the QB site, the relaxation of fluorescence decay arising from S2QA - recombination was somewhat faster in Acaryochloris marina than in Synechocystis PCC 6803. Thermoluminescence intensity of the so called B band, arising from the recombination of the S2QB- charge separated state, was enhanced significantly (2.5 fold) on the basis of equal amounts of PSII in Acaryochloris marina as compared with Synechocystis 6803. Our data show that the energetics of charge recombination is modified in Acaryochloris marina leading to a ∼15 meV decrease of the free energy gap between the QA and QB acceptors. In addition, the total free energy gap between the ground state and the excited state of the reaction center chlorophyll is at least ∼25-30 meV smaller in Acaryochloris marina, suggesting that the primary donor species cannot consist entirely of Chl a in Acaryochloris marina, and there is a contribution from Chl d as well.

Original languageEnglish
Pages (from-to)131-140
Number of pages10
JournalPhotosynthesis research
Volume98
Issue number1-3
DOIs
Publication statusPublished - Oct 1 2008

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Keywords

  • Acaryochloris marina
  • Charge separation
  • Chlorophyll d
  • Electron transfer
  • Fluorescence
  • Photosystem II
  • Thermoluminescence

ASJC Scopus subject areas

  • Biochemistry
  • Plant Science
  • Cell Biology

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