PHOTOSYNTHETICA

Photosynthetica 2018, 56(1):229-235 | DOI: 10.1007/s11099-018-0775-y

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

V. Hartmann¹, A. Ruff², W. Schuhmann², M. Rögner¹, M. M. Nowaczyk^1,*

¹ Plant Biochemistry, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany

² Analytical Chemistry-Center for Electrochemical Science (CES), Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Bochum, Germany

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^+*/Q_A^-* charge recombination and thus less efficient photon-to-charge conversion, whereas PsbA1-PSII is optimised for efficient electron transfer with limited stability.

Additional key words: biophotovoltaics; cyanobacteria; D1-protein; hydrogel

Received: July 17, 2017; Accepted: November 28, 2017; Published: March 1, 2018  Show citation