title: Can we trap the S(3)Y(Z)· metalloradical intermediate during the S-state transitions of Photosystem II? An EPR investigation.
abstract: We report the trapping of two metalloradical intermediates corresponding to the transitions S2 to S3 and S3 to S0 of the oxygen evolving complex (OEC) of Photosystem II (PSII), in preparations containing methanol, at temperatures near that of half inhibition of the respective S-state transitions. The first intermediate, with an EPR width of 160 G, is assigned to S2YZ, based on its similarity to the one previously characterized after trapping at 10 K. The second with a splitting of ∼80 G is tentatively assigned to S3YZ. The S3YZ EPR signal is weaker than the S2YZ one, and both are stable at cryogenic temperatures.
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology & Microsystems, NCSR "Demokritos", Athens 15310, Greece.
authors.forename: Georgia
authors.initials: G
authors.lastname: Zahariou
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology & Microsystems, NCSR "Demokritos", Athens 15310, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Chrysina
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology & Microsystems, NCSR "Demokritos", Athens 15310, Greece.
authors.forename: Vasili
authors.initials: V
authors.lastname: Petrouleas
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology & Microsystems, NCSR "Demokritos", Athens 15310, Greece. Electronic address: nioannid@ims.demokritos.gr.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Ioannidis
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D055550:Protein Stability; D019097:Spin Trapping; D018724:Spinacia oleracea
chemical_list: D005609:Free Radicals; D045332:Photosystem II Protein Complex; D008345:Manganese
keywords: Metalloradical; Photosystem II