title: Parallel polarization electron paramagnetic resonance studies of the S1-state manganese cluster in the photosynthetic oxygen-evolving system.
abstract: Magnetic properties of the S1-state manganese cluster in the oxygen-evolving photosystem II were studied by parallel polarization electron paramagnetic resonance spectroscopy. Dark minus light spectra gave rise to a broad S1-state signal with a g value of about 4.9 [Dexheimer, S. L., Klein, M. P. (1992) J. Am. Chem. Soc. 114, 2821-2826]. Temperature variation of the signal intensity between 1.9 and 10 K observed in PS II with a sucrose buffer indicates that the signal originates from an excited state with a spin S of 1 with separation from the ground state (S = 0) of about 2.5 K. The S1-state signal was also observed in the sucrose buffer supplemented by 50% glycerol. However, no S1-state signal was detected by addition of 3% methanol or 30% ethylene glycol in the sucrose buffer, although illumination at 200 K in the presence of these alcohols induced the normal multiline S2 signal. Furthermore, modification of the Mn cluster by Cl- or Ca2+ depletion from PS II membranes failed to produce a detectable S1-state signal. A possible magnetic structure of the Mn cluster responsible for the generation of the S1-state signal is discussed on the basis of these observations.
authors.affiliation: Faculty of Science, Kwansei Gakuin University, Nishinomiya, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamauchi
authors.forename: H
authors.initials: H
authors.lastname: Mino
authors.forename: T
authors.initials: T
authors.lastname: Matsukawa
authors.forename: A
authors.initials: A
authors.lastname: Kawamori
authors.forename: T
authors.initials: T
authors.lastname: Ono
mesh_terms: D002021:Buffers; D002118:Calcium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D008433:Mathematics; D000432:Methanol; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D018724:Spinacia oleracea / Q000737:chemistry; D013395:Sucrose; D013696:Temperature
chemical_list: D002021:Buffers; D002712:Chlorides; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D008345:Manganese; D013395:Sucrose; D010100:Oxygen; D002118:Calcium; D000432:Methanol