Evidence map›Paper›PMID 18766464›Full record

ArticlePhotosynthesis research

Quantum efficiency distributions of photo-induced side-pathway donor oxidation at cryogenic temperature in photosystem II.

Joseph L Hughes, A William Rutherford, Miwa Sugiura, Elmars Krausz

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Article in Photosynthesis research. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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4 authors.

Joseph L HughesResearch School of Chemistry, The Australian National University, Canberra, ACT 0200, Australia. joseph.hughes@cea.fr
A William Rutherford
Miwa Sugiura
Elmars Krausz

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

We monitored illuminated-minus-dark absorption difference spectra in the range of 450-1100 nm induced by continuous illumination at 8 K of photosystem II (PSII) core complexes from Thermosynechococcus elongatus. The photo-induced oxidation of the side-path donors Cytb(559), beta-carotene and chlorophyll Z, as well as the concomitant stable (t(1/2) > 1 s) reduction of the first plastoquinone electron acceptor, Q(A) (monitored by the well-known 'C550' shift), were quantified as a function of the absorbed photons per PSII. The Q(A) photo-induced reduction data can be described by three distinct quantum efficiency distributions: (i) a very high efficiency of approximately 0.5-1, (ii) a middle efficiency with a very large range of approximately 0.014-0.2, and (iii) a low efficiency of approximately 0.002. Each of the observed side-path donors exhibited similar quantum efficiency distributions, which supports a branched pathway model for side-path oxidation where beta-carotene is the immediate electron donor to the photo-oxidized chlorophyll (P680(+)). The yields of the observed side-path donors account quantitatively for the wide middle efficiency range of photo-induced Q(A) reduction, but not for the PSII fractions that exhibit the highest and lowest efficiencies. The high-efficiency component may be due to Tyr(Z) oxidation. A donor that does not exhibit an identified absorption in the visible-near-IR region is mainly responsible for the lowest efficiency component.

Indexed as

Cold TemperatureElectron TransportCyanobacteriaOxidation-ReductionPhotosynthesisPhotosystem II Protein ComplexSpectrum AnalysisPhotosystem II Protein Complex

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