title: g-Anisotropy of the S2-state manganese cluster in single crystals of cyanobacterial photosystem II studied by W-band electron paramagnetic resonance spectroscopy.
abstract: The multiline signal from the S2-state manganese cluster in the oxygen evolving complex of photosystem II (PSII) was observed in single crystals of a thermophilic cyanobacterium Thermosynechococcus vulcanus for the first time by W-band (94 GHz) electron paramagnetic resonance (EPR). At W-band, spectra were characterized by the g-anisotropy, which enabled the precise determination of the tensor. Distinct hyperfine splittings (hfs's) as seen in frozen solutions of PSII at X-band (9.5 GHz) were detected in most of the crystal orientations relative to the magnetic field. In some orientations, however, the hfs's disappeared due to overlapping of a large number of EPR lines from eight crystallographic symmetry-related sites of the manganese cluster within the unit cell of the crystal. Analysis of the orientation-dependent spectral features yielded the following g-tensor components: g(x) = 1.988, g(y) = 1.981, g(z) = 1.965. The principal values suggested an approximate axial symmetry around the Mn(III) ion in the cluster.
authors.affiliation: Institute for Molecular Science, Okazaki 444-8585, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Matsuoka
authors.forename: Ko
authors.initials: K
authors.lastname: Furukawa
authors.forename: Tatsuhisa
authors.initials: T
authors.lastname: Kato
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mino
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Asako
authors.initials: A
authors.lastname: Kawamori
mesh_terms: D003460:Crystallization; D000458:Cyanobacteria / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008345:Manganese / Q000737:chemistry*; D045332:Photosystem II Protein Complex / Q000737:chemistry*
chemical_list: D045332:Photosystem II Protein Complex; D008345:Manganese