title: The first room-temperature X-ray absorption spectra of higher oxidation states of the tetra-manganese complex of photosystem II.
abstract: The manganese (Mn) complex of photosystem II catalyzes water oxidation. For the first time, its advancement through the reaction cycle was monitored by time-resolved X-ray absorption measurements at the Mn K-edge at room temperature. The complex was stepped through its four oxidation states by nano-second-laser flashes applied to samples exposed to the X-ray beam. Time courses of the X-ray fluorescence intensity were recorded during a flash sequence. Extended X-ray absorption fine-structure spectra were recorded with the S(1), S(2), and S(3) oxidation states highly populated. The room temperature data is compatible with the formation of a third di-mu-oxo bridge between two Mn atoms upon the S(2)-->S(3) transition.
authors.affiliation: Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195, Berlin, Germany. holger.dau@physik.fu-berlin.de
authors.forename: Michael
authors.initials: M
authors.lastname: Haumann
authors.forename: Markus
authors.initials: M
authors.lastname: Grabolle
authors.forename: Thomas
authors.initials: T
authors.lastname: Neisius
authors.forename: Holger
authors.initials: H
authors.lastname: Dau
mesh_terms: D007834:Lasers; D008345:Manganese / Q000378:metabolism*; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D013053:Spectrophotometry; D018724:Spinacia oleracea; D014965:X-Rays
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D008345:Manganese