Light-Dependent Paramagnetic Centers in the Photosynthesis of Higher Plants

IV INTRODUCTION 66 A. Structure of the Photosynthetic Apparatus of Green Plants 66 B. General Scheme of Electron Transport in the Photosynthesis of Higher Plants 67 C. The Main Types of ESR Signals Observed in Photosynthetic Systems 68 D. The Main Problems Solvable by the ESR Technique 70 PARMAGNETIC CENTERS AT EARLY STAGES OF LIGHT-INDUCED CHARGE SEPARATION IN PHOTOSYSTEM I '. 70 A. Chlorophyll Functions in Photosynthesis 70 B. The Primary Electron Donor in Photosystem I: Pigment P700 70 C. The System of Bound Electron Acceptors of Photosystem 1 76 D. Bound Fe-S Centers on the Reducing Side of Photosystem 1 83 OTHER ELECTRON DONORS AND ACCEPTORS OF PHOTOSYSTEM I 87 A. Soluble Ferredoxin 87 B. Flavodoxin 88 C. Ferredoxin-NADP Reductase 89 D. The Reactions on the Oxidizing Side of Photosystem 1 89 PRIMARY REACTIONS IN PHOTOSYSTEM II 90 A. The Scheme of Electron-Transport Reactions in Photosystem II 90 B. ESR Signals from Oxidized Chlorophyll in Photosystem II 91 C. Bound Acceptors in Photosystem II 94 V. ESR SIGNAL II AND THE REACTIONS ON THE OXIDIZING SIDE OF PHOTOSYSTEM II 94 VI. Mn (II) IONS ANDTHE WATER-SPLITTING SYSTEM 97 A. Charge Accumulation in the Water-Splitting System 97 B. ESR Spectra of Hydrated Mn(ll) Ions 98 C. Displacement, Binding, and Photooxidation of Mn(ll) Ions by Chloroplasts 98 D. Mn in Chloroplasts as a Relaxant of Water Protons 100 E. The Cluster Nature of the Mn Centers in Chloroplasts .... 101 F. Alternative Hypotheses on the Structure of the Water-Splitting Complex 101 G. C.I" Ions in the Water-Splitting System and the Mn(ll) Signal with Superhyperfine Structure 102 VII.NONCYCLIC ELECTRON TRANSPORT BETWEEN THE TWO PHOTOSYSTEMS 103 A. Spectral-Kinetic Separation of the Two Photosystems ...103 B. The Two-Electron Shutter in the Noncyclic Electron-Transport Chain 105 C. The High-Potential Fe-S Center in a Noncyclic Chain 107 VIII. CONCLUSIONS 108