Download or read book Mechanisms of Decarboxylation Internal Return Water Addition and Their Isotope Effects written by Scott Owen Chelmsford Mundle and published by . This book was released on 2010 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2-(2-mandelyl)thiamin (MTh), the adduct of benzoylformate and thiamin, is an accurate model of 2-(2-mandelyl)thiamin diphosphate, the initial covalent intermediate in the decarboxylation of benzoylformate by benzoylformate decarboxylase (BFDC). The first order rate constant for spontaneous decarboxylation of MTh is about 106 times smaller than the enzymic rate ( kcat) for the BFDC reaction. Based on the similarities of MTh and the corresponding enzymic intermediate, as well as the inherent nature of the intermediate, it is not obvious why the enzyme-catalyzed reaction is so much faster. However, earlier studies showed that the decarboxylation of MTh is catalyzed by protonated pyridines and this was proposed to occur through a preassociation mechanism. If this explanation is correct, then the observed 12C/13C kinetic isotope effect (CKIE) will increase in the presence of the catalyst as a more favorable forward commitment is made possible. This provides a specific model for the enzyme-catalyzed process.We developed a technique using headspace analysis and compound specific isotope analysis (CSIA) to determine the CKIE for the decarboxylation of MTh in the presence and absence of pyridinium. We found that the CKIE increases in the presence of the catalyst, as predicted for the preassociation mechanism.In a related study, we investigated the kinetics of decarboxylation of pyrrole-2-carboxylic acid, which was known to be subject to acid catalysis in highly acidic solutions. In the expected mechanism, protonation of the pyrrole ring at C2 destroys the aromaticity of the ring. C-C bond cleavage in the process of decarboxylation will reestablish the aromatic pyrrole. However, the overall reaction rate would not increase as it is counteracted by a larger concentration of the undissociated carboxyl group compared to carboxylate ion necessary for decarboxylation.Since the reaction occurs readily, there must be an alternative pathway for the acid-catalyzed reaction. This can be achieved in an associative mechanism that is initiated by addition of water to the carboxyl group of the carboxyl-protonated reactant. C-C bond cleavage results in formation of pyrrole and protonated carbonic acid, a species that has been recognized as a viable intermediate in related processes. Protonated carbonic acid is spontaneously converted to H3O+ and carbon dioxide. The associative mechanism is consistent with solvent-deuterium kinetic isotope effects and 12C/13C kinetic isotope effects.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1970 with total page 930 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition States of Biochemical Processes written by R. Gandour and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 625 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transItIOn-state theory has been, from the point of its inception, the most influential principle in the development of our knowledge of reaction mechanisms in solution. It is natural that as the field of biochemical dynamics has achieved new levels of refinement its students have increasingly adopted the concepts and methods of transition-state theory. Indeed, every dynamical problem of biochemistry finds its most elegant and economical statement in the terms of this theory. Enzyme catalytic power, for example, derives from the interaction of enzyme and substrate structures in the transition state, so that an understanding of this power must grow from a knowledge of these structures and interactions. Similarly, transition-state interactions, and the way in which they change as protein structure is altered, constitute the pivotal feature upon which molecular evolution must turn. The complete, coupled dynamical system of the organism, incorporating the transport of matter and energy as well as local chemical processes, will eventually have to yield to a description of its component transition-state structures and their energetic response characteristics, even if the form of the description goes beyond present-day transition-state theory. Finally, the importance of biochemical effectors in medicine and agriculture carries the subject into the world of practical affairs, in the use of transition-state information for the construction of ultra potent biological agents.
Download or read book Reaction Rates of Isotopic Molecules written by Lars C. S. Melander and published by . This book was released on 1987 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Encyclopedia of Ecology written by Brian D. Fath and published by Elsevier. This book was released on 2018-08-23 with total page 2786 pages. Available in PDF, EPUB and Kindle. Book excerpt: Encyclopedia of Ecology, Second Edition, Four Volume Set continues the acclaimed work of the previous edition published in 2008. It covers all scales of biological organization, from organisms, to populations, to communities and ecosystems. Laboratory, field, simulation modelling, and theoretical approaches are presented to show how living systems sustain structure and function in space and time. New areas of focus include micro- and macro scales, molecular and genetic ecology, and global ecology (e.g., climate change, earth transformations, ecosystem services, and the food-water-energy nexus) are included. In addition, new, international experts in ecology contribute on a variety of topics. Offers the most broad-ranging and comprehensive resource available in the field of ecology Provides foundational content and suggests further reading Incorporates the expertise of over 500 outstanding investigators in the field of ecology, including top young scientists with both research and teaching experience Includes multimedia resources, such as an Interactive Map Viewer and links to a CSDMS (Community Surface Dynamics Modeling System), an open-source platform for modelers to share and link models dealing with earth system processes
Download or read book Isotope Effects In Chemistry and Biology written by Amnon Kohen and published by CRC Press. This book was released on 2005-11-01 with total page 1092 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of isotope effects has expanded exponentially in the last decade, and researchers are finding isotopes increasingly useful in their studies. Bringing literature on the subject up to date, Isotope Effects in Chemistry and Biology covers current principles, methods, and a broad range of applications of isotope effects in the physical, biolo
Download or read book Heavy atom Kinetic Isotope Effects written by Marvin J. Stern and published by . This book was released on 1972 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Sci tech Book Profiles written by and published by . This book was released on 1965 with total page 856 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes title page, table of contents, list of contributors, preface and all indexes of each book.
Download or read book Understanding Organometallic Reaction Mechanisms and Catalysis written by Valentin P. Ananikov and published by John Wiley & Sons. This book was released on 2014-08-29 with total page 483 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exploring and highlighting the new horizons in the studies of reaction mechanisms that open joint application of experimental studies and theoretical calculations is the goal of this book. The latest insights and developments in the mechanistic studies of organometallic reactions and catalytic processes are presented and reviewed. The book adopts a unique approach, exemplifying how to use experiments, spectroscopy measurements, and computational methods to reveal reaction pathways and molecular structures of catalysts, rather than concentrating solely on one discipline. The result is a deeper understanding of the underlying reaction mechanism and correlation between molecular structure and reactivity. The contributions represent a wealth of first-hand information from renowned experts working in these disciplines, covering such topics as activation of small molecules, C-C and C-Heteroatom bonds formation, cross-coupling reactions, carbon dioxide converison, homogeneous and heterogeneous transition metal catalysis and metal-graphene systems. With the knowledge gained, the reader will be able to improve existing reaction protocols and rationally design more efficient catalysts or selective reactions. An indispensable source of information for synthetic, analytical, and theoretical chemists in academia and industry.
Download or read book Photosynthesis Physiology and Metabolism written by Richard C. Leegood and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photosynthesis: Physiology and Metabolism is the we have concentrated on the acquisition and ninth volume in theseries Advances in Photosynthesis metabolism of carbon. However, a full understanding (Series Editor, Govindjee). Several volumes in this of reactions involved in the conversion of to series have dealt with molecular and biophysical sugars requires an integrated view of metabolism. aspects of photosynthesis in the bacteria, algae and We have, therefore, commissioned international cyanobacteria, focussing largely on what have been authorities to write chapters on, for example, traditionally, though inaccurately, termed the ‘light interactionsbetween carbon and nitrogen metabolism, reactions’(Volume 1, The Molecular Biology of on respiration in photosynthetic tissues and on the Cyanobacteria;Volume2,AnoxygenicPhotosynthetic control of gene expression by metabolism. Photo- Bacteria, Volume 3, Biophysical Techniques in synthetic carbon assimilation is also one of the most Photosynthesis and Volume 7, The Molecular Biology rapid metabolic processes that occurs in plant cells, of the Chloroplasts and Mitochondria in Chlamy- and therefore has to be considered in relation to domonas). Volume 4 dealt with Oxygenic Photo- transport, whether it be the initial uptake of carbon, synthesis: The Light Reactions, and volume 5 with intracellular transport between organelles, inter- Photosynthesis and the Environment, whereas the cellular transport, as occurs in plants, or transport structure and function of lipids in photosynthesis of photosynthates through and out of the leaf. All was covered in Volume 6 of this series: Lipids in these aspects of transport are also covered in the Photosynthesis: Structure, Function and Genetics, book.
Download or read book Mechanisms of Catalysis written by and published by Academic Press. This book was released on 1991-01-28 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: The remarkable expansion of information leading to a deeper understanding of enzymes on the molecular level necessitated the development of this volume which not only introduces new topics to The Enzymes series but presents new information on some covered in Volume I and II of this edition.
Download or read book Biochemical Models of Leaf Photosynthesis written by Susanna Von Caemmerer and published by CSIRO PUBLISHING. This book was released on 2000 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing concerns of global climatic change have stimulated research in all aspects of carbon exchange. This has restored interest in leaf-photosynthetic models to predict and assess changes in photosynthetic CO2 assimilation in different environments. This is a comprehensive presentation of the most widely used models of steady-state photosynthesis by an author who is a world authority. Treatments of C3, C4 and intermediate pathways of photosynthesis in relation to environment have been updated to include work on antisense transgenic plants. It will be a standard reference for the formal analysis of photosynthetic metabolism in vivo by advanced students and researchers.
Download or read book Federation Proceedings written by and published by . This book was released on 1971 with total page 1872 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Art of Writing Reasonable Organic Reaction Mechanisms written by Robert B. Grossman and published by Springer Science & Business Media. This book was released on 2007-07-31 with total page 371 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intended for students of intermediate organic chemistry, this text shows how to write a reasonable mechanism for an organic chemical transformation. The discussion is organized by types of mechanisms and the conditions under which the reaction is executed, rather than by the overall reaction as is the case in most textbooks. Each chapter discusses common mechanistic pathways and suggests practical tips for drawing them. Worked problems are included in the discussion of each mechanism, and "common error alerts" are scattered throughout the text to warn readers about pitfalls and misconceptions that bedevil students. Each chapter is capped by a large problem set.
Download or read book Pandex Current Index to Scientific and Technical Literature written by and published by . This book was released on 1971 with total page 1334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mitochondria and Anaerobic Energy Metabolism in Eukaryotes written by William F. Martin and published by Walter de Gruyter GmbH & Co KG. This book was released on 2020-12-07 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mitochondria are sometimes called the powerhouses of eukaryotic cells, because mitochondria are the site of ATP synthesis in the cell. ATP is the universal energy currency, it provides the power that runs all other life processes. Humans need oxygen to survive because of ATP synthesis in mitochondria. The sugars from our diet are converted to carbon dioxide in mitochondria in a process that requires oxygen. Just like a fire needs oxygen to burn, our mitochondria need oxygen to make ATP. From textbooks and popular literature one can easily get the impression that all mitochondria require oxygen. But that is not the case. There are many groups of organismsm known that make ATP in mitochondria without the help of oxygen. They have preserved biochemical relicts from the early evolution of eukaryotic cells, which took place during times in Earth history when there was hardly any oxygen avaiable, certainly not enough to breathe. How the anaerobic forms of mitochondria work, in which organisms they occur, and how the eukaryotic anaerobes that possess them fit into the larger picture of rising atmospheric oxygen during Earth history are the topic of this book.
Download or read book Stable Isotope Geochemistry written by John W. Valley and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-12-17 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 43 of Reviews in Mineralogy and Geochemistry follows the 1986 Reviews in Mineralogy (Vol. 16) in approach but reflects significant changes in the field of Stable Isotope Geochemistry. In terms of new technology, new sub-disciplines, and numbers of researchers, the field has changed more in the past decade than in any other since that of its birth. Unlike the 1986 volume, which was restricted to high temperature fields, this book covers a wider range of disciplines. However, it would not be possible to fit a comprehensive review into a single volume. Our goal is to provide state-of-the-art reviews in chosen subjects that have emerged or advanced greatly since 1986. This volume was prepared for Short Course on Stable Isotope Geochemistry presented November 2-4, 2001 in conjunction with the annual meetings of the Geological Society of America in Boston, Massachusetts.
