title: ENDOR studies of the intermediate electron acceptor radical anion I-. in Photosystem II reaction centers.
abstract: The EPR and ENDOR characteristics of the intermediate electron acceptor radical anion I-. in Photosystem II (PS II) are shown to be identical in membrane particles and in the D1D2 cytochrome b-559 complex (Nanba, O. and Satoh, K. (1987) Proc. Natl. Acad. Sci. USA 84, 109-112). These findings provide further evidence that the D1D2 complex is the reaction center of PS II and show that the pheophytin binding site is intact. A hydrogen bond between I-. and the protein (GLU D1-130) is postulated on the basis of D2O exchange experiments. The ENDOR data of I-. and of the pheophytin a radical anion in different organic solvents are compared and the observed differences are related to structural changes of the molecule on the basis of molecular orbital calculations (RHF-INDO/SP). The importance of the orientation of the vinyl group (attached to ring I) on electron transfer is discussed.
authors.affiliation: Institut für Organische Chemie, Freie Universität, Berlin, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Lubitz
authors.forename: R A
authors.initials: RA
authors.lastname: Isaacson
authors.forename: M Y
authors.initials: MY
authors.lastname: Okamura
authors.forename: E C
authors.initials: EC
authors.lastname: Abresch
authors.forename: M
authors.initials: M
authors.lastname: Plato
authors.forename: G
authors.initials: G
authors.lastname: Feher
mesh_terms: D000838:Anions; D002734:Chlorophyll / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D003573:Cytochrome b Group / Q000378:metabolism; D004579:Electron Transport; D004583:Electrons; D005609:Free Radicals; D006860:Hydrogen Bonding; D045342:Light-Harvesting Protein Complexes; D015394:Molecular Structure; D010674:Pheophytins / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000378:metabolism*; D011522:Protons; D013057:Spectrum Analysis
chemical_list: D000838:Anions; D003573:Cytochrome b Group; D005609:Free Radicals; D045342:Light-Harvesting Protein Complexes; D010674:Pheophytins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011522:Protons; D002734:Chlorophyll; C061694:pheophytin a; C019313:cytochrome b559