title: Evidence for the presence of a component of the Mn complex of the photosystem II reaction centre which is exposed to water in the S(2) state of the water oxidation complex.
abstract: The interaction of water oxidising photosystem II preparations with the aqueous environment has been investigated using electron spin echo envelope modulation spectroscopy in the presence of 2H(2)O. The spectra show interaction of 2H of 2H(2)O with the preparation in the S(2) state. The component interacting with water decays during 1-4 weeks storage at 77 K. No interaction of water with the classical multiline S(2) Mn signal, which is more stable on storage at 77 K, was detected. The results show that a component of the water oxidation complex, possibly involving the Mn centre, is accessible to water and may be the water binding site for photosynthetic water oxidation.
authors.affiliation: Department of Biology, University College London, Gower St., WC1E 6BT, London, UK. mike.evans@ucl.ac.uk
authors.forename: M C
authors.initials: MC
authors.lastname: Evans
authors.forename: A M
authors.initials: AM
authors.lastname: Rich
authors.forename: J H
authors.initials: JH
authors.lastname: Nugent
mesh_terms: D001665:Binding Sites; D003624:Darkness; D003903:Deuterium / Q000378:metabolism; D004237:Diuron / Q000494:pharmacology; D004356:Drug Storage; D004578:Electron Spin Resonance Spectroscopy; D004795:Enzyme Stability; D008027:Light; D008345:Manganese / Q000378:metabolism*; D016877:Oxidants / Q000378:metabolism; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000201:enzymology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000378:metabolism*
chemical_list: D016877:Oxidants; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D014867:Water; D008345:Manganese; D004237:Diuron; D003903:Deuterium