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Role of missing carotenoid in reducing the fluorescence of single monomeric photosystem II core complexes

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Abstract

The fluorescence of monomeric photosystem II core complexes (mPSIIcc) of the cyanobacterium Thermosynechococcus elongatus, originating from redissolved crystals, is investigated by using single-molecule spectroscopy (SMS) at 1.6 K. The emission spectra of individual mPSIIcc are dominated by sharp zero-phonon lines, showing the existence of different emitters compatible with the F685, F689, and F695 bands reported formerly. The intensity of F695 is reduced in single mPSIIcc as compared to single PSIIcc-dimers (dPSIIcc). Crystal structures show that one of the β-carotene (β-Car) cofactors located at the monomer–monomer interface in dPSIIcc is missing in mPSIIcc. This β-Car in dPSIIcc is in van der Waals distance to chlorophyll (Chl) 17 in the CP47 subunit. We suggest that this Chl contributes to the F695 emitter. A loss of β-Car cofactors in mPSIIcc preparations will lead to an increased lifetime of the triplet state of Chl 17, which can explain the reduced singlet emission of F695 as observed in SMS.

Graphical abstract: Role of missing carotenoid in reducing the fluorescence of single monomeric photosystem II core complexes

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Publication details

The article was received on 12 Nov 2016, accepted on 25 Apr 2017 and first published on 28 Apr 2017


Article type: Paper
DOI: 10.1039/C6CP07748J
Citation: Phys. Chem. Chem. Phys., 2017, Advance Article
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    Role of missing carotenoid in reducing the fluorescence of single monomeric photosystem II core complexes

    S. Skandary, F. Müh, I. Ashraf, M. Ibrahim, M. Metzger, A. Zouni, A. J. Meixner and M. Brecht, Phys. Chem. Chem. Phys., 2017, Advance Article , DOI: 10.1039/C6CP07748J

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