Electrochemically produced hydrogen peroxide affects Joliot-type oxygen-evolution measurements of photosystem II

• Published in: Biochimica et biophysica acta Vol. 1837; no. 9; pp. 1411 - 1416
• Main Authors: Pham, Long Vo, Messinger, Johannes
• Format: Journal Article
• Language: English
• Published: Netherlands 01.09.2014
• Subjects: Electrochemistry; hydrogen peroxide (H2O2); Hydrogen Peroxide - chemistry; Manganese; Oxygen - chemistry; oxygen evolving complex (OEC); photosystem II (PSII); Photosystem II Protein Complex - chemistry; Water oxidation; Photosystem II (PSII); Hydrogen peroxide (HO); Oxygen evolving complex (OEC); Water oxidation; Manganese
• ISSN: 0006-3002; 0005-2728; 1879-2650
• DOI: 10.1016/j.bbabio.2014.01.013

The main technique employed to characterize the efficiency of water-splitting in photosynthetic preparations in terms of miss and double hit parameters and for the determination of Si (i=2,3,0) state lifetimes is the measurement of flash-induced oxygen oscillation pattern on bare platinum (Joliot-type) electrodes. We demonstrate here that this technique is not innocent. Polarization of the electrode against an Ag/AgCl electrode leads to a time-dependent formation of hydrogen peroxide by two-electron reduction of dissolved oxygen continuously supplied by the flow buffer. While the miss and double hit parameters are almost unaffected by H₂O₂, a time dependent reduction of S1 to S₋₁ occurs over a time period of 20 min. The S1 reduction can be largely prevented by adding catalase or by removing O₂ from the flow buffer with N₂. Importantly, we demonstrate that even at the shortest possible polarization times (40s in our set up) the S₂ and S₀ decays are significantly accelerated by the side reaction with H₂O₂. The removal of hydrogen peroxide leads to unperturbed S₂ state data that reveal three instead of the traditionally reported two phases of decay. In addition, even under the best conditions (catalase+N₂; 40s polarization) about 4% of S₋₁ state is observed in well dark-adapted samples, likely indicating limitations of the equal fit approach. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.