title: Competing charge transfer pathways at the photosystem II-electrode interface.
abstract: The integration of the water-oxidation enzyme photosystem II (PSII) into electrodes allows the electrons extracted from water oxidation to be harnessed for enzyme characterization and to drive novel endergonic reactions. However, PSII continues to underperform in integrated photoelectrochemical systems despite extensive optimization efforts. Here we carried out protein-film photoelectrochemistry using spinach and Thermosynechococcus elongatus PSII, and we identified a competing charge transfer pathway at the enzyme-electrode interface that short-circuits the known water-oxidation pathway. This undesirable pathway occurs as a result of photo-induced O2reduction occurring at the chlorophyll pigments and is promoted by the embedment of PSII in an electron-conducting fullerene matrix, a common strategy for enzyme immobilization. Anaerobicity helps to recover the PSII photoresponse and unmasks the onset potentials relating to the QA/QBcharge transfer process. These findings impart a fuller understanding of the charge transfer pathways within PSII and at photosystem-electrode interfaces, which will lead to more rational design of pigment-containing photoelectrodes in general.
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, UK.
authors.forename: Jenny Z
authors.initials: JZ
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, UK.
authors.forename: Katarzyna P
authors.initials: KP
authors.lastname: Sokol
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Paul
authors.affiliation: Department of Physics and Astronomy, VU Amsterdam, Amsterdam, The Netherlands.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Romero
authors.affiliation: Department of Physics and Astronomy, VU Amsterdam, Amsterdam, The Netherlands.
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, UK.
authors.forename: Erwin
authors.initials: E
authors.lastname: Reisner
mesh_terms: D000458:Cyanobacteria / Q000201:enzymology; D055664:Electrochemical Techniques; D004566:Electrodes; D004579:Electron Transport; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D055668:Photochemical Processes; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D014867:Water; D010100:Oxygen