Electron Transfer, Hydrogen and Peptide Bonds


Book Description

Current Organic Chemistry, Volume 14, Number 2, 2010 ISSN: 1385-2728. eISSN: 1875-534 Contents Editorial p.89 Towards “Ab-initio” Computations of Electron Transfer Rates: the Early Electron Transfer Steps in Bacterial Photosynthetic Reaction Centers Andrea Peluso p.90 Theoretical Analysis of the Contributions Made by CH••OH Bonds to Protein Structure Steven Scheiner p.106 Theoretical Insights into Dispersion and Hydrogen-Bonding Interactions in Biomolecular Systems Alexander Pavlov and Petar M. Mitrasinovic p.129 Advances in Bioconjugation Jeet Kalia and Ronald T. Raines p.138 Chemically Engineered Ribosomes: A New Frontier in Synthetic Biology Anna Chirkova, Matthias Erlacher, Ronald Micura and Norbert Polacek p.148 Conformational Electrostatics in the Stabilization of the Peptide Anion Janet S. Anderson, Griselda Hernández and David M. LeMaster p.162 Atoms-in-Molecules Dual Functional Analysis of Weak to Strong Interactions Waro Nakanishi and Satoko Hayashi p.181 Electronic Processes at Organic/Metal Interfaces: Recent Progress and Pitfalls Petar M. Mitrasinovic p.198










Hydrogen Bonding and Transfer in the Excited State


Book Description

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.







Hydrogen-bonding Research In Photochemistry, Photobiology, And Optoelectronic Materials


Book Description

As one of the typical intermolecular interactions, hydrogen-bonding plays a significant role in molecular structure and function. When the hydrogen bond research system is connected with the photon, the hydrogen-bonding effect turns to an excited-state one influencing photochemistry, photobiology, and photophysics. Thus, the hydrogen bond in an excited state is a key topic for understanding the excited-state properties, especially for optoelectronic or luminescent materials.The approaches presented in this book include quantum chemical calculation, molecular dynamics simulation and ultrafast spectroscopy, which are strong tools to investigate the hydrogen bond. Unlike other existing titles, this book combines theoretical calculations and experiments to explore the nature of excited-state hydrogen bonds. By using these methods, more details and faster processes involved in excited-state dynamics of hydrogen bond are explored.This highly interdisciplinary book provides an overview of leading hydrogen bond research. It is essential reading for faculties and students in researching photochemistry, photobiology and photophysics, as well as novel optoelectronic materials, fluorescence probes and photocatalysts. It will also guide research beginners to getting a quick start within this field.




Electron and Proton Transfer in Chemistry and Biology


Book Description

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.




Intraprotein Electron Transfer Reactions Facilitated by Aromatic Amino Acids and Their Protein Microenvironments


Book Description

Intraprotein electron transfer processes are crucial to the maintenance of cellular pathways that enable life as we know. Well-studied and well-characterized proteins such as cytochrome c and azurin have long been used to explore these processes. The pathways present in these proteins and others, while varying in length can include covalent bonds, hydrogen bonds, and through-space jumps. Of interest are interactions in yeast cytochrome c that are similar to hydrogen bonds. We aimed to explore a pathway where the hydroxyl of Tyr67 interacts with the Met80 sulfur. To probe the importance of the interaction in the context of electron transfer, Tyr67 was replaced with different fluorotyrosines of varying pKas. We then evaluated a second pathway containing two hydrogen bonds of which were removed by mutating to different amino acids. The elimination of these hydrogen bonds did not influence the rate of intramolecular electron transfer so an alternative pathway was examined. From this pathway, a substitution to Met64 to increase the length of a through-space jump decreased the electron transfer rate by a factor of two suggesting the initial pathway is non-operative. Lastly, the protein, azurin, was used as a model to investigate the properties of unnatural fluorotyrosines. The Trp48 amino acid was replaced with various fluorotyrosines in order to develop a system where the unnatural amino acid properties can be probed in relation to electron transfer processes.




Molecular-Scale Electronics


Book Description

Provides in-depth knowledge on molecular electronics and emphasizes the techniques for designing molecular junctions with controlled functionalities This comprehensive book covers the major advances with the most general applicability in the field of molecular electronic devices. It emphasizes new insights into the development of efficient platform methodologies for building such reliable devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. It also helps to develop an understanding of the device fabrication processes and the characteristics of the resulting electrode-molecule interface. Beginning with an introduction to the subject, Molecular-Scale Electronics: Concept, Fabrication and Applications offers full chapter coverage on topics such as: Metal Electrodes for Molecular Electronics; Carbon Electrodes for Molecular Electronics; Other Electrodes for Molecular Electronics; Novel Phenomena in Single-Molecule Junctions; and Supramolecular Interactions in Single-Molecule Junctions. Other chapters discuss Theoretical Aspects for Electron Transport through Molecular Junctions; Characterization Techniques for Molecular Electronics; and Integrating Molecular Functionalities into Electrical Circuits. The book finishes with a summary of the primary challenges facing the field and offers an outlook at its future. * Summarizes a number of different approaches for forming molecular-scale junctions and discusses various experimental techniques for examining these nanoscale circuits in detail * Gives overview of characterization techniques and theoretical simulations for molecular electronics * Highlights the major contributions and new concepts of integrating molecular functionalities into electrical circuits * Provides a critical discussion of limitations and main challenges that still exist for the development of molecular electronics * Suited for readers studying or doing research in the broad fields of Nano/molecular electronics and other device-related fields Molecular-Scale Electronics is an excellent book for materials scientists, electrochemists, electronics engineers, physical chemists, polymer chemists, and solid-state chemists. It will also benefit physicists, semiconductor physicists, engineering scientists, and surface chemists.




Mechanistic Study of Hydrogen Bonding and Proton Coupled Electron Transfer in Two Separate Redox Systems, Each Containing a Phenylenediamine Derivative


Book Description

This thesis presents a mechanistic study of two phenylenediamine derivatives. The first is a disubstituted phenylenediamine with a phenyl-urea substituted para to a dimethylamino group. The phenyl-urea moiety offers two N-H sites for hydrogen bonding and proton transfer. This is UHH. The second, is a disubstituted phenylenediamine with an isocytosine-urea moiety substituted para to a dimethylamino group. The combined isocytosine-urea-phenylenediamine forms a redox active 4-hydrogen bond array where the urea moiety offers two N-H sites for proton donation and the isocytosine offers two sites for hydrogen bond acceptance. This is UpyH. Initial cyclic voltammetry (CV) experiments for UHH show reversible CV behavior in CH2Cl2 and irreversible CV behavior in CH3CN. With the inclusion of two UHH analogs, one with both N-H sites "blocked" with methyl substituents, UMeMe, and a second analog with a single urea N-H site, UMeMe, CV analysis continued. From these studies, in addition to a UV-vis/ CV study, it was determined that the dimethylamino on a fully reduced UHH or UMeH could abstract a proton from a second radical cation urea N-H. This was immediately followed by a thermodynamically favorable second electron transfer. Thus the products at the end of the first oxidation wave from a 2 e-, 1H+ transfer are a quinoidal cation and a fully reduced/protonated UHH or UMeH. On the return scan, UHH in CH3CN and UMeH in both solvents undergo a thermodynamically non-favored back proton transfer at a more energetic reduction potential. UHH in CH2Cl2 accesses a lower energy pathway through the formation of a hydrogen bond complex as part of a wedge scheme. Both pathways are supported by results from concentration and scan rate dependent CV studies that show two return waves correlating to two pathways. UV-vis results show a protonated/reduced species, but no radical cation. In the UpyH project, by using the same CV and UV-vis analysis in addition to an 1HNMR study in CH2Cl2/NBu4PF6, we show UpyH favors a dimerized form but as the dimer undergoes oxidation it breaks apart then reforms on the return scan. To our knowledge this the first account for electrochemically breaking apart a Upy derivative.