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Oxygenic Photoreactivity in Photosystem II Studied by Rotating Ring Disk Electrochemistry.

Published version
Peer-reviewed

Type

Article

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Authors

Kornienko, Nikolay 
Zhang, Jenny Z 
Sokol, Katarzyna P 
Lamaison, Sarah 
Fantuzzi, Andrea 

Abstract

Protein film photoelectrochemistry has previously been used to monitor the activity of photosystem II, the water-plastoquinone photooxidoreductase, but the mechanistic information attainable from a three-electrode setup has remained limited. Here we introduce the four-electrode rotating ring disk electrode technique for quantifying light-driven reaction kinetics and mechanistic pathways in real time at the enzyme-electrode interface. This setup allows us to study photochemical H2O oxidation in photosystem II and to gain an in-depth understanding of pathways that generate reactive oxygen species. The results show that photosystem II reacts with O2 through two main pathways that both involve a superoxide intermediate to produce H2O2. The first pathway involves the established chlorophyll triplet-mediated formation of singlet oxygen, which is followed by its reduction to superoxide at the electrode surface. The second pathway is specific for the enzyme/electrode interface: an exposed antenna chlorophyll is sufficiently close to the electrode for rapid injection of an electron to form a highly reducing chlorophyll anion, which reacts with O2 in solution to produce O2•-. Incomplete H2O oxidation does not significantly contribute to reactive oxygen formation in our conditions. The rotating ring disk electrode technique allows the chemical reactivity of photosystem II to be studied electrochemically and opens several avenues for future investigation.

Description

Keywords

0306 Physical Chemistry (incl. Structural)

Journal Title

J Am Chem Soc

Conference Name

Journal ISSN

0002-7863
1520-5126

Volume Title

140

Publisher

American Chemical Society (ACS)
Sponsorship
European Research Council (682833)
Royal Society Newton International Fellowship, ERC Consollidator Grant, BBSRC, EPSRC, French Corps of Bridges, Waters & Forests, VU University Amsterdam, ERC Advanced Investigator grant, EU FP7 project, Academy Professor grant from the Netherlands Royal Academy of Sciences
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