title: Near-infrared-induced transitions in the manganese cluster of photosystem II: action spectra for the S2 and S3 redox states.
abstract: The Mn4Ca complex that is involved in water oxidation in PSII is affected by near-infrared (NIR) light in certain redox states and these phenomena can be monitored by electron paramagnetic resonance (EPR) at low temperature. Here we report the action spectra of the NIR effects in the S2 and S3 states in PSII from plants and the thermophilic cyanobacterium Thermosynechococcus elongatus. The action spectra obtained are very similar in both S states, indicating the presence of the same photoactive form of the Mn4Ca complex in both states. Since the chemical nature of the photoactive species is not known, an unequivocal interpretation of this result cannot be made; however, it appears to be more easily reconciled with the view that the redox state of the Mn4Ca cluster does not change from the S2 to the S3 transition, at least in those centers sensitive to NIR light. The temperature dependence of the NIR effect and the action spectra for S2 indicate the presence of structural heterogeneity in the Mn4Ca cluster.
authors.affiliation: Service de Bioénergétique, DBJC, URA CNRS 2096, CEA Saclay, 91191 Gif-sur-Yvette, France. alain.boussac@cea.fr
authors.forename: Alain
authors.initials: A
authors.lastname: Boussac
authors.forename: Miwa
authors.initials: M
authors.lastname: Sugiura
authors.forename: Diana
authors.initials: D
authors.lastname: Kirilovsky
authors.forename: A William
authors.initials: AW
authors.lastname: Rutherford
mesh_terms: D002118:Calcium / Q000737:chemistry; D000458:Cyanobacteria / Q000737:chemistry / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D007259:Infrared Rays; D008345:Manganese / Q000737:chemistry; D010084:Oxidation-Reduction; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000528:radiation effects*; D018724:Spinacia oleracea / Q000737:chemistry / Q000528:radiation effects; D013696:Temperature; D014443:Tyrosine / Q000737:chemistry
chemical_list: D045332:Photosystem II Protein Complex; D014443:Tyrosine; D008345:Manganese; D002118:Calcium