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Split EPR signals from photosystem II are modified by methanol, reflecting S state-dependent binding and alterations in the magnetic coupling in the CaMn4 cluster.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
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2006 (English)In: Biochemistry, ISSN 0006-2960, Vol. 45, no 24, 7617-27 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2006. Vol. 45, no 24, 7617-27 p.
Keyword [en]
Binding Sites, Comparative Study, Dose-Response Relationship; Drug, Electron Spin Resonance Spectroscopy, Lasers, Light, Magnetics, Methanol/*pharmacology, Photosynthetic Reaction Center Complex Proteins/chemistry/genetics/*metabolism, Photosystem II Protein Complex/*metabolism, Protein Binding/drug effects, Research Support; Non-U.S. Gov't, Signal Transduction/drug effects, Spinacia oleracea/metabolism
Identifiers
URN: urn:nbn:se:uu:diva-81367PubMedID: 16768457OAI: oai:DiVA.org:uu-81367DiVA: diva2:109282
Available from: 2006-08-18 Created: 2006-08-18 Last updated: 2011-01-11
In thesis
1. EPR Studies of Photosystem II: Characterizing Water Oxidizing Intermediates at Cryogenic Temperatures
Open this publication in new window or tab >>EPR Studies of Photosystem II: Characterizing Water Oxidizing Intermediates at Cryogenic Temperatures
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The principles of natures own light-driven water splitting catalyst, Photosystem II (PSII), can in the future inspire us to use water as electron and proton source to generate light-driven H2 production. To mimic this challenging step, it is important to understand how the enzyme system can oxidize water. The mechanism of light-driven water oxidation in PSII is in this thesis addressed by EPR spectroscopy. P680+ is a strong oxidant formed by light-oxidation of the chlorophyll species P680 positioned in the center of PSII. The redox active tyrosine-Z (YZ) can reduce P680+ and the YZ radical is formed. This transient radical is further reduced by the CaMn4-cluster, which is the binding site of the substrate water molecules. In a cyclic process called the S-cycle, this catalytic cluster accumulates four oxidizing equivalents to evolve one molecule of O2 and to oxidize two molecules of water. We can induce the YZ radical at cryogenic temperatures in the different oxidation states of the catalytic S-cycle and observe this in metalloradical EPR signals. These metalloradical EPR signals are here characterized and used to deduce mechanistic information from the intact PSII. The "double nature" of these spin-spin interaction signals, so called split EPR signals, makes them excellent probes to both YZ oxidation and, when YZ is present, also to the S-states of the CaMn4-cluster. The metalloradical EPR signals presented here, form a way to study the transient YZ radical in active PSII that has not been depleted of the catalytic metal cluster. This depleting method that has often been used in the past to study YZ is not representing studies of a mechanistically relevant material. The previously suggested disorder around YZ and accessibility to the bulk can be artifactual properties induced in the mechanistically defect PSII. On the contrary, our observation that proton coupled electron transfer from YZ to the light induced P680+ can occur in a high yield at cryogenic temperatures, suggests a well ordered catalytic site in the protein positioned for optimal performance. The optimized positioning of the redox components found in PSII might be a feature also important to build in an efficient water oxidizing catalyst.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 72 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 621
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-99109 (URN)978-91-554-7458-4 (ISBN)
Public defence
2009-04-24, Häggsalen, Ångströmslabortoriet, Lägerhyddsvägen 1, Uppsala, 13:00 (English)
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Available from: 2009-04-03 Created: 2009-03-09 Last updated: 2010-01-13Bibliographically approved

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Mamedov, FikretStyring, Stenbjörn

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