Download or read book Chemical Complementation Studies of Proton coupled Electron Transfer Reactions in Photosystem II written by Anna-Maria Andrea Hays and published by . This book was released on 1999 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proton Coupled Electron Transfer written by Sebastiao Formosinho and published by Royal Society of Chemistry. This book was released on 2011-12-07 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton-coupled electron transfer (PCET) is emerging as an important new class of reactions and, over the past decade, great strides have been made in our understanding of them. PCET reactions are studied in many branches of chemistry and are omnipresent in biological processes. This book covers recent developments from both the theoretical and experimental points of view. It concentrates on the importance of PCET in biological systems and for bioenergetic conversion. The oxidation of water in Photosystem II to produce oxygen, and the reduction of protons to hydrogen by hydrogenase, for energy storage gets particular emphasis. Chemical reactivity is currently explained in terms of several scientific principles. One of them is the bond-breaking-bond-forming process and is conceptually based on potential energy surfaces. Another incorporates the role of Franck-Condon factors resulting from the overlap of vibrational wavefunctions. A third, the so-called solvent reorganization, involves solvent configuration around a charged species. PCET brings together such concepts and links them to quantum mechanical tunnelling of the electron particle. This book uses personal accounts of experimental examples to provide additional insight on this important topic. It starts by presenting a general overview of the main theoretical approaches and experimental applications. The chapters then go on to cover topics including: the application of the Marcus Cross Relation; the solvation of ionic systems; experimental approaches in biological redox systems; metal ion-coupled electron transfer, and electrochemical concerted proton-electron transfers.
Download or read book The Tuning of Electron and Proton coupled Electron Transfer Reactions of Solar Water Oxidation Pulsed Magnetic Resonance Spectroscopy Studies of Photosystem II written by Christopher S. Coates and published by . This book was released on 2013 with total page 784 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Mechanisms of Proton coupled Electron Transfer and Water Oxidation in Photosystem II written by Shin Nakamura and published by Springer Nature. This book was released on 2020-01-03 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 CO2, but also as an O2 source in the atmosphere. Water oxidation takes place at the Mn4CaO5 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.
Download or read book Redox Active Tyrosines in Photosystem II written by James M. Keough and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton coupled electron transfer reactions often involve tyrosine residues, because when oxidized, the phenolic side chain deprotonates. Tyrosine Z (YZ) is responsible for extracting electrons in a stepwise fashion from the oxygen evolving-complex in order to build enough potential to oxidize water. This process requires that each step YZ must deprotonate and reprotonate in order to maintain the high midpoint potential that is necessary to oxidize the oxygen-evolving complex, which makes YZ highly involved in proton coupled electron transfer reactions. In this thesis YZ has been studied within oxygen-evolving photosystem II utilizing electron paramagnetic resonance spectroscopy to monitor the tyrosyl radical that is formed upon light excitation. Kinetic analysis of YZ has shed light on the factors that are important for PSII to carry out water oxidation at the oxygen-evolving complex. Most notably the strong hydrogen-bonding network and the midpoint potential of YZ have been shown to be integral aspects of the water splitting reactions of PSII. By studying YZ within oxygen-evolving PSII, conclusions are readily applied to the native system.
Download or read book Electron and Proton Transfer in Chemistry and Biology written by Achim Müller and published by Elsevier Publishing Company. This book was released on 1992 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various aspects of electron and proton transfer in chemistry and biology are described in this volume. The joint presentation was chosen for two reasons. Rapid electron and proton transfer govern cellular energetics in both the most primitive and higher organisms with photosynthetic and heterotrophic lifestyles. Further, biology has become the area where the various disciplines of science, which were previously diversified, are once again converging. The book begins with a survey of physicochemical principles of electron transfer in the gas and solid phase, with thermodynamic and photochemical driving force. Inner and outer sphere mechanisms and the coupling of electron transfer to nuclear rearrangements are reviewed. These principles are applied to construct artificial photosynthesis, leading to biological electron transfer involving proteins with transition metal and/or organic redox centres. The tuning of the free energy profile on the reaction trajectory through the protein by single amino acids or by the larger ensemble that determines the electrostatic properties of the reaction path is one major issue.Another one is the transformation of one-electron to paired-electron steps with protection against hazardous radical intermediates. The diversity of electron transport systems is represented in various chapters with emphasis on photosynthesis, respiration and nitrogenases. The book will be of interest to scientists in chemistry, physics and the life sciences.
Download or read book Photosystem II written by T. Wydrzynski and published by Springer Science & Business Media. This book was released on 2006-01-27 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most mysterious part of photosynthesis yet the most important for all aerobic life on Earth (including ourselves) is how green plants, algae and cyanobacteria make atmospheric oxygen from water. This thermodynamically difficult process is only achieved in Nature by the unique pigment/protein complex known as Photosystem II, using sunlight to power the reaction. The present volume contains 34 comprehensive chapters authored by 75 scientific experts from around the world. It gives an up-to-date account on all what is currently known about the molecular biology, biochemistry, biophysics and physiology of Photosystem II. The book is divided into several parts detailing the protein constituents, functional sites, tertiary structure, molecular dynamics, and mechanisms of homeostasis. The book ends with a comparison of Photosystem II with other related enzymes and bio-mimetic systems. Since the unique water-splitting chemistry catalyzed by Photosystem II leads to the production of pure oxygen gas and has the potential for making hydrogen gas, a primary goal of this book is to provide a molecular guide to future protein engineers and bio-mimetic chemists in the development of biocatalysts for the generation of clean, renewable energy from sunlight and water.
Download or read book Photosynthetic Water Oxidation and Proton coupled Electron Transfer written by Ian Blake Cooper and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Photosystem II (PSII) is the membrane-bound oxidoreductase peptide complex responsible for the oxidation of water to molecular oxygen and reduction of plastoquinone to plastoquinol. Primary electron transfer is initiated upon absorption of a photon by the primary donor chl resulting in electron transfer and production of a P680+QA charge separated state. P680+ is reduced by YZ (Y161 of the D1 polypeptide subunit), one of two redox-active tyrosine residues found in PSII. This produces a neutral tyrosyl radical (YZ) which is subsequently reduced by electrons derived from water at the oxygen-evolving complex (OEC). The OEC is composed of four manganese, one calcium ion, and one chloride ion. Four photons are required to convert water to O2, each photon advancing the OEC through successive oxidation states or S states. The exact chemical mechanism of water oxidation in PSII is not known. However, proton-coupled electron transfer (PCET) is thought to be one of the fundamental steps in driving the extraction of electrons and protons from water. Here, the mechanism of water oxidation is investigated with focus on PCET events using vibrational spectroscopy. Vibrational spectroscopy is sensitive to changes in protein structure, charge, and hydrogen bonding, and is ideal for the study of fast events coupled with light-induced electron transfer. The results presented here demonstrate the utility of time-resolved infrared spectroscopy in the detection of intermediates of photosynthetic water oxidation. We suggest that proton transfer may precede manganese oxidation during water oxidation based on time-resolved infrared and difference FT-IR spectroscopic results. The mechanism of PCET associated with YZ reduction is investigated. Using reaction-induced difference FT-IR spectroscopy, the identity of the chloride binding site is speculated through the use of bromide exchange at the OEC. Also, proton transfer reactions at the OEC are investigated using azide as a vibrational probe. The advances in the understanding of photosynthetic water oxidation gained in this work will aid in the elucidation of the chemical mechanism of this important reaction. Understanding the details of photosynthetic water oxidation will assist in the development of technology aimed at harnessing the energy of the sun for the benefit of humankind.
Download or read book Mechanistic Studies of Proton coupled Electron Transfer Reactions Involving Antioxidants written by Kejie Meng and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the research was to investigate proton-coupled electron transfer (PCET) reactions involving antioxidants to gain insight into the detailed mechanisms of glutathione (GSH), Trolox, and [alpha]-tocopherol ([alpha]-TOH). PCET reactions are complex redox reactions that transfer electrons and protons sequentially or in concert. These reactions are ubiquitous in natural or artificial processes that produce electrochemical energy that is extractable as electricity or as chemical fuels of high energy content. Examples of processes based on PCET are photosynthesis, respiration, nitrogen fixation, carbon dioxide reduction, redox fuel cells, and artificial photosynthesis. Antioxidants were selected as a PCET model to understand the coupling between proton transfer (PT) and electron transfer (ET) in order to elucidate structure-reactivity relationships under different experimental conditions. PCET reactions were studied with a set of electrochemical techniques to propose a preliminary mechanism that could be validated with digital simulations matching the electrochemical response. In some cases, other analytical techniques were used to aid in the system characterization. This thesis presents the results and discussion of the effects of oxidant-base pairs on the mediated oxidation of GSH, the -2e−-H process of Trolox in aqueous and nonaqueous solvents with various pH values, and the particle collision electrolysis of [alpha]-tocopherol in oil-in-water emulsion droplets on an ultramicroelectrode. Ultimately our goal was to determine the kinetic and thermodynamic factors that control PCET reactions so that they can be applied in designing artificial systems for the production of energy using more abundant reagents with lower cost and better yields.
Download or read book Modeling the TyrZ His 190 Pair of Photosystem II for the Study of Proton Coupled Electron Transfer written by Dustin Patterson and published by . This book was released on 2011 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work described in the thesis involves the synthesis of a molecular triad which is designed to undergo proton coupled electron transfer (PCET) upon irradiation with light. Photoinduced PCET is an important process that many organisms use and the elucidation of its mechanism will allow further understanding of this process and its potential applications. The target compound designed for PCET studies consists of a porphyrin chromophore (also a primary electron donor), covalently linked to a phenol-imidazole (secondary electron donor), and a C60 (primary electron acceptor). The phenol-imidazole moiety of this system is modeled after the TyrZ His-190 residues in the reaction center of Photosystem II (PS II). These residues participate in an intermolecular H-bond between the phenol side chain of TyrZ and the imidazole side chain of His-190. The phenol side chain of TyrZ is the electron transfer mediator between the oxygen evolving complex (OEC) and P680 (primary electron donor) in PSII. During electron transfer from TyrZ to P680*+, the phenolic proton of TyrZ becomes highly acidic (pKa~-2) and the hydrogen is preferentially transferred to the relatively basic imidazole of His-190 through a pre-existing hydrogen bond. This PCET process avoids a charged intermediate, on TyrZ, and results in a neutral phenolic radical (TyrZ*). The current research consists of building a molecular triad, which can mimic the photoinduced PCET process of PSII. The following, documents the synthetic progress in the synthesis of a molecular triad designed to investigate the mechanism of PCET as well as gain further insight on how this process can be applied in artificial photosynthetic devices.
Download or read book Mechanistic Studies of Photo induced Proton coupled Electron Transfer and Oxygen Atom Transfer Reactions in Model Systems written by Justin Mark Hodgkiss and published by . This book was released on 2006 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) The observed PCET rates are strongly attenuated compared with comparable covalentlybridged analogues, indicating that the PT interface reduces electronic coupling. Temperature-isotope dependence of the PCET rates reveals an unusual inverse isotope effect at low temperature, which is interpreted in a model of vibrationally-assisted PCET (chapter IV). Hangman porphyrin dyads have been developed to study bi-directional PCET in relation to oxygen activation. ET and PT coordinates are orthogonalized at fixed distances about a FeIII-OH center (Chapters V and VI). TA spectroscopy and electronic structure calculations reveal that the structural reorganization attendant to metal-centered PCET imposes a severe kinetic cost and alternative quenching pathways prevail. Finally, TA spectroscopy has been used to elucidate the mechanism of photocatalytic OAT for bridged diiron [mu]-oxo bisporphyrins (Chapter VII). The [mu]-oxo bond is photo-cleaved to generate a terminal iron(IV) oxo, which undergoes OAT to nucleophilic substrates. OAT rates are maximized when the bridge actively splays the porphyrin subunits apart to present the oxo before reclamping can occur.
Download or read book Photosynthesis written by Julian J. Eaton-Rye and published by Springer Science & Business Media. This book was released on 2011-11-04 with total page 874 pages. Available in PDF, EPUB and Kindle. Book excerpt: “Photosynthesis: Plastid Biology, Energy Conversion and Carbon Assimilation” was conceived as a comprehensive treatment touching on most of the processes important for photosynthesis. Most of the chapters provide a broad coverage that, it is hoped, will be accessible to advanced undergraduates, graduate students, and researchers looking to broaden their knowledge of photosynthesis. For biologists, biochemists, and biophysicists, this volume will provide quick background understanding for the breadth of issues in photosynthesis that are important in research and instructional settings. This volume will be of interest to advanced undergraduates in plant biology, and plant biochemistry and to graduate students and instructors wanting a single reference volume on the latest understanding of the critical components of photosynthesis.
Download or read book Oxygenic Photosynthesis The Light Reactions written by Donald R. Ort and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 681 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structure and function of the components of the photosynthetic apparatus and the molecular biology of these components have become the dominant themes in advances in our understanding of the light reactions of oxygenic photosynthesis. Oxygenic Photosynthesis: The Light Reactions presents our current understanding of these reactions in thylakoid membranes. Topics covered include the photosystems, the cytochrome b6-f complex, plastocyanin, ferredoxin, FNR, light-harvesting complexes, and the coupling factor. Chapters are also devoted to the structure of thylakoid membranes, their lipid composition, and their biogenesis. Updates on the crystal structures of cytochrome f, ATP synthase and photosystem I are presented and a section on molecular biology and evolution of the photosynthetic apparatus is also included. The chapters in this book provide a comprehensive overview of photosynthetic reactions in eukaryotic thylakoids. The book is intended for a wide audience, including graduate students and researchers active in this field, as well as those individuals who have interests in plant biochemistry and molecular biology or plant physiology.
Download or read book Natural and Artificial Photosynthesis written by Reza Razeghifard and published by John Wiley & Sons. This book was released on 2013-08-23 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: This technical book explores current and future applications of solar power as an unlimited source of energy that earth receives every day. Photosynthetic organisms have learned to utilize this abundant source of energy by converting it into high-energy biochemical compounds. Inspired by the efficient conversion of solar energy into an electron flow, attempts have been made to construct artificial photosynthetic systems capable of establishing a charge separation state for generating electricity or driving chemical reactions. Another important aspect of photosynthesis is the CO2 fixation and the production of high energy compounds. Photosynthesis can produce biomass using solar energy while reducing the CO2 level in air. Biomass can be converted into biofuels such as biodiesel and bioethanol. Under certain conditions, photosynthetic organisms can also produce hydrogen gas which is one of the cleanest sources of energy.
Download or read book Hydrogen Bonding and Transfer in the Excited State written by Ke-Li Han and published by John Wiley & Sons. This book was released on 2011-03-16 with total page 1229 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives an extensive description of the state-of-the-art in research on excited-state hydrogen bonding and hydrogen transfer in recent years. Initial chapters present both the experimental and theoretical investigations on the excited-state hydrogen bonding structures and dynamics of many organic and biological chromophores. Following this, several chapters describe the influences of the excited-state hydrogen bonding on various photophysical processes and photochemical reactions, for example: hydrogen bonding effects on fluorescence emission behaviors and photoisomerization; the role of hydrogen bonding in photosynthetic water splitting; photoinduced electron transfer and solvation dynamics in room temperature ionic liquids; and hydrogen bonding barrier crossing dynamics at bio-mimicking surfaces. Finally, the book examines experimental and theoretical studies on the nature and control of excited-state hydrogen transfer in various systems. Hydrogen Bonding and Transfer in the Excited State is an essential overview of this increasingly important field of study, surveying the entire field over 2 volumes, 40 chapters and 1200 pages. It will find a place on the bookshelves of researchers in photochemistry, photobiology, photophysics, physical chemistry and chemical physics.
Download or read book Photosynthesis written by G. Garab and published by Springer Science & Business Media. This book was released on 1998-12-15 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photosynthesis is a process on which virtually all life on Earth depends. To answer the basic questions at all levels of complexity, from molecules to ecosystems, and to establish correlations and interactions between these levels, photosynthesis research - perhaps more than any other discipline in biology - requires a multidisciplinary approach. Congresses probably provide the only forums where progress throughout the whole field can be overviewed. The Congress proceedings give faithful pictures of recent advances in photosynthesis research and outline trends and perspectives in all areas, ranging from molecular events to aspects of photosynthesis on the global scale. The Proceedings Book, a set of 4 (or 5) volumes, is traditionally highly recognized and intensely quoted in the literature, and is found on the shelves of most senior scientists in the field and in all major libraries.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2000 with total page 956 pages. Available in PDF, EPUB and Kindle. Book excerpt:
