title: EPR properties of a g=2 broad signal trapped in an S1 state in Ca2+-depleted Photosystem II.
abstract: We investigated a new EPR signal that gives a broad line shape around g=2 in Ca(2+)-depleted Photosystem (PS) II. The signal was trapped by illumination at 243 K in parallel with the formation of Y(Z)*. The ratio of the intensities between the g=2 broad signal and the Y(Z)* signal was 1:3, assuming a Gaussian line shape for the former. The g=2 broad signal and the Y(Z)* signal decayed together in parallel with the appearance of the S(2) state multiline at 243 K. The g=2 broad signal was assigned to be an intermediate S(1)X* state in the transition from the S(1) to the S(2) state, where X* represents an amino acid radical nearby manganese cluster, such as D1-His337. The signal is in thermal equilibrium with Y(Z)*. Possible reactions in the S state transitions in Ca(2+)-depleted PS II were discussed.
authors.affiliation: Division of Material Science (Physics), Graduate School of Science, Nagoya University, Furocyo, Chikusa, Nagoya 464-8602, Japan. mino@bio.phys.nagoya-u.ac.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mino
authors.forename: Shigeru
authors.initials: S
authors.lastname: Itoh
mesh_terms: D002118:Calcium / Q000032:analysis / Q000378:metabolism; D003624:Darkness; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D018724:Spinacia oleracea / Q000378:metabolism / Q000648:ultrastructure; D013696:Temperature; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D045332:Photosystem II Protein Complex; C114979:tyrosyl radical YZ; D014443:Tyrosine; D008345:Manganese; D002118:Calcium