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Analysis of photosystem II electron transfer with natural PsbA-variants by redox polymer/protein biophotoelectrochemistry

Hartmann, V. and Ruff, A. and Schuhmann, W. and Rögner, M. and Nowaczyk, M.M.

PHOTOSYNTHETICA
Volume: Pages: 1-7
DOI: 10.1007/s11099-018-0775-y
Published: 2018

Abstract
Redox polymer/protein biophotoelectrochemistry was used to analyse forward electron transfer of isolated PSII complexes with natural PsbA-variants. PsbA1- or PsbA3-PSII was embedded in a redox hydrogel that allows diffusion-free electron transfer to the electrode surface and thus measurement of an immediate photocurrent response. The initial photocurrent density of the electrode is up to ~2-fold higher with PsbA1-PSII under all tested light conditions, the most prominent under high-light [2,300 μmol(photon) m–2 s–1] illumination with 5 μA cm–2 for PsbA3-PSII and 9.5 μA cm–2 for PsbA1-PSII. This indicates more efficient electron transfer in low-light-adapted PsbA1-PSII. In contrast, the photocurrent decays faster in PsbA1-PSII under all tested light conditions, which suggests increased stability of high-light-adapted PsbA3-PSII. These results confirm and extend previous observations that PsbA3-PSII has increased P680+·/QA –· charge recombination and thus less efficient photon-to-charge conversion, whereas PsbA1-PSII is optimised for efficient electron transfer with limited stability. © 2018 The Institute of Experimental Botany

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