title: 55Mn pulse ENDOR at 34 GHz of the S0 and S2 states of the oxygen-evolving complex in photosystem II.
abstract: 55Mn pulse ENDOR experiments at 34 GHz (Q-band) are reported for the S0 and S2 states of the oxygen-evolving complex of photosystem II. Their numerical analysis (i) shows that in both states all four Mn ions are magnetically coupled, (ii) allows a refinement of the hyperfine interaction (HFI) parameters obtained earlier for the S2 state at X-band (Peloquin, J. M.; Campbell, K. A.; Randall, D. W.; Evanchik, M. A.; Pecoraro, V. L.; Armstrong, W. H.; Britt, R. D. J. Am. Chem. Soc. 2000, 122, 10926-10942), (iii) provides the first reliable 55Mn HFI tensors for the S0 state, and (iv) leads to the suggestion that the Mn oxidation states in S0 and S2 are Mn4(III, III, III, IV) and Mn4(III, IV, IV, IV), respectively. In addition, a Q-band EPR spectrum is reported for the S0 state, and inversion-recovery experiments at 4.5 K directly show that the electron spin-lattice relaxation for the S0 state is about 2 orders of magnitude faster than that for the S2 state.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim/Ruhr, Germany.
authors.forename: Leonid V
authors.initials: LV
authors.lastname: Kulik
authors.forename: Boris
authors.initials: B
authors.lastname: Epel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
authors.forename: Johannes
authors.initials: J
authors.lastname: Messinger
mesh_terms: D002118:Calcium / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010777:Photochemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D045332:Photosystem II Protein Complex; D008345:Manganese; D010100:Oxygen; D002118:Calcium