Photocurrents from photosystem II in a metal oxide hybrid system: electron transfer pathways

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Title: Photocurrents from photosystem II in a metal oxide hybrid system: electron transfer pathways
Authors: Brinkert, K
Le formal, F
Li, X
Durrant, J
Rutherford, AW
Fantuzzi, A
Item Type: Journal Article
Abstract: We have investigated the nature of the photocurrent generated by Photosystem II (PSII), the water oxidizing enzyme, isolated from Thermosynechococcus elongatus, when immobilized on nanostructured titanium dioxide on an indium tin oxide electrode (TiO2/ITO). We investigated the properties of the photocurrent from PSII when immobilized as a monolayer versus multilayers, in the presence and absence of an inhibitor that binds to the site of the exchangeable quinone (QB) and in the presence and absence of exogenous mobile electron carriers (mediators). The findings indicate that electron transfer occurs from the first quinone (QA) directly to the electrode surface but that the electron transfer through the nanostructured metal oxide is the rate-limiting step. Redox mediators enhance the photocurrent by taking electrons from the nanostructured semiconductor surface to the ITO electrode surface not from PSII. This is demonstrated by photocurrent enhancement using a mediator incapable of accepting electrons from PSII. This model for electron transfer also explains anomalies reported in the literature using similar and related systems. The slow rate of the electron transfer step in the TiO2 is due to the energy level of electron injection into the semiconducting material being below the conduction band. This limits the usefulness of the present hybrid electrode. Strategies to overcome this kinetic limitation are discussed.
Issue Date: 3-Mar-2016
Date of Acceptance: 1-Mar-2016
ISSN: 0005-2728
Publisher: Elsevier
Start Page: 1497
End Page: 1505
Journal / Book Title: Biochimica et Biophysica Acta-Bioenergetics
Volume: 1857
Issue: 9
Copyright Statement: © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (
Sponsor/Funder: Commission of the European Communities
The Royal Society
Biotechnology and Biological Sciences Research Council (BBSRC)
Commission of the European Communities
Funder's Grant Number: 291482
Keywords: Photosynthesis
Photosynthetic reaction centre
Protein electrode interface
Protein film photoelectrochemistry
Water oxidizing enzyme
0601 Biochemistry And Cell Biology
06 Biological Sciences
02 Physical Sciences
Publication Status: Published
Appears in Collections:Chemistry
Faculty of Natural Sciences

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