Molecular Mechanisms of Proton-coupled Electron Transfer and Water Oxidation in Photosystem II (Springer Theses)

The book reviews photosynthetic water oxidation and proton-coupled electron transfer in photosystem, focusing on the molecular vibrations of amino acid residues and water molecules. Photosynthetic water oxidation performed by plants and cyanobacteria is essential for the sustenance of life on Earth, not only as an electron source for synthesizing sugars from CO 2 , but also as an O 2 source in the atmosphere. Water oxidation takes place at the Mn 4 CaO 5 cluster in photosystem II, where a series of electron transfer reactions coupled with proton transfer occur using light energy. The author addresses the unresolved mechanisms of photosynthetic water oxidation and relevant proton-coupled electron transfer reactions using a combined approach of experimental and computational methods such as Fourier transform infrared difference spectroscopy and quantum chemical calculations. The results show that protonation and hydrogen-bond structures of water molecules and amino acid residues in the protein play important roles in regulation of the electron and proton transfer reactions. These findings and the methodology make a significant contribution to our understanding the molecular mechanism of photosynthetic water oxidation. Supervisor’s Foreword 6 Parts of this thesis have been published in the following journal articles: 7 Acknowledgements 8 Contents 9 Abbreviations 11 1 General Introduction 12 1.1 Photosystem II 12 1.2 Fourier Transform Infrared Spectroscopy (FTIR) 15 1.3 Quantum Chemical Calculation 17 1.4 Purpose of This Study 17 References 19 2 Hydrogen Bond Structure of Redox Active Tyrosines in Photosystem II 22 2.1 Introduction 22 2.2 Materials and Methods 24 2.3 Results 27 2.4 Discussion 38 References 43 3 Proton Release Reaction of Tyrosine D in Photosystem II 48 3.1 Introduction 48 3.2 Materials and Methods 49 3.3 Results 51 3.4 Discussion 56 References 59 4 Vibrational Analysis of Water Network Around the Mn Cluster 63 4.1 Introduction 63 4.2 Materials and Methods 64 4.3 Results 65 4.4 Discussion 70 References 73 5 Vibrational Analysis of Carboxylate Ligands in the Water Oxidizing Center 77 5.1 Introduction 77 5.2 Materials and Methods 79 5.3 Results 80 5.4 Discussion 96 References 101 6 Protonation Structure of a Key Histidine in the Water Oxidizing Center 105 6.1 Introduction 105 6.2 Materials and Methods 107 6.3 Results 110 6.4 Discussion 121 References 128 7 General Conclusion 133 Curriculum Vitae 135