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Author: Pascale Marie Noëlle Tiger
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Pascale Marie Noëlle Tiger
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Pavel Hobza
Publisher: Elsevier Science & Technology
ISBN:
Category : Science
Languages : en
Pages : 256
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Author: J Duchesne
Publisher: Elsevier
ISBN: 0323159516
Category : Science
Languages : en
Pages : 236
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Physico-chemical Properties of Nucleic Acids, Volume III revolves around three major concepts, which are intra- and intermolecular interactions, radiation effects in DNA cells, and repair mechanisms. This volume also presents the stage of specific biological functions and how repair mechanisms relate to the problem of evolution. Comprised of six chapters, this volume begins with the concept of renaturation of polynucleotides. Interactions in nucleic acids and nucleotides are discussed in several chapters. Other topics covered in this volume include polymer and salt-induced condensation of DNA and strand-breaks in the DNA of mammalian cells. The last chapter explores the stability and evolution of DNA in terms of molecular radiobiology. This chapter also presents and reviews some evolutionary problems, specifically the prebiotic evolution. The elements of stabilization and variability of genetic information are also discussed in the last chapter. As with the other volumes, this volume is a valuable reference for students and researchers in the fields of chemistry, biology, molecular biology, microbiology, and biophysics.
Author: H. J. Keller
Publisher: Springer
ISBN: 1489970312
Category : Technology & Engineering
Languages : en
Pages : 353
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Book Description
Theoretical and experimental work on solids with low-dimensi℗Ư onal cooperative phenomena has been rather explosively expanded in the last few years, and it seems to be quite fashionable to con℗Ư tribute to this field, especially to the problem of one-dimensional metals. On the whole, one could divide the huge amount of recent investigations into two parts although there is much overlap bet℗Ư ween these regimes, namely investigations on magnetic exchange interactions constrained to mainly one or two dimensions and, secondly, work done on Id metallic solids or linear chain compounds with Id delocalized electrons. There is, of course, overlap from one extreme case to the other with these solids and in some rare cases both phenomena are studied on one and the same crystal. In fact, however, most of the scientific groups in this area could be associated roughly with one of these categories and, in addition, a separation between theoreticians and experimentalists in each of these groups leads to a further splitting of interests although many theories about these solids have been tested by experimenta℗Ư lists. Nevertheless, more cooperation and understanding between scientists working on low-dimensional cooperative phenomena should appreciably stimulate further development. With a better inderdis℗Ư ciplinary understanding, new ideas could possibly help chemists in synthesizing tailor-cut solids. This would in return give experi℗Ư mentalists new phenomena to examine and finally would stimulate new theoretical work.
Author: Ahmed Mohammed Ali Said
Publisher:
ISBN:
Category :
Languages : en
Pages : 423
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A fundamental principle in all biological processes is molecular recognition and organization. Molecular recognition is the process of selective, multiple weak non-covalent interactions, like hydrogen bonding and electrostatic interactions, between two molecular entities to form a complex such as in a ligand-receptor interaction. This process is very complex in that it involves enthalpy, entropy and desolvation changes. Understanding molecular recognition at a fundamental level is very important to alter the activity of proteins, which is the underlying principle of "The Rational Drug Design". Scoring functions, and other computational methods, have been widely used by medicinal chemists in an attempt to accurately predict ligand binding affinity to its protein host with the aim of aiding efforts directed towards rational drug design. Thus far the accuracy of these scoring functions predictions is generally limited. This is partly because of the commonly made inaccurate assumption that non-covalent interactions, such as hydrogen bonding and van der Waals interactions, between the ligand and the protein host, always behave in an additive way. Some of the fundamentals of non-covalent interactions, such as enthalpy-entropy compensation, role of water in the binding, and ligand functional groups' cooperativity, are typically not included in these calculations. It is the aim of this work to uncover different types of ligand functional groups' cooperative contributions to the binding affinity, and to address how different factors in the ligand structure can affect the magnitude of that cooperativity. The serine protease thrombin was selected to be the protein model system, and several series of thrombin inhibitors were designed, synthesized and biologically tested in our lab. The aim from this was to provide a more in depth understanding for different types of ligand functional groups' cooperativity. In chapter 1, a brief theoretical background on ligand-protein binding affinity is provided, and some of the underappreciated non-covalent fundamentals are discussed, such as the hydrophobic effect, ligand-protein conformational changes, enthalpy-entropy compensation and cooperativity. In chapter 2, we revealed a positive cooperativity between a H-bonding group and an adjacent hydrophobic side chain using two congenic series of thrombin inhibitors. The first series are m-chlorobenzyl containing inhibitors, and we found a positive cooperativity between the ligand carbonyl group, which makes H-bond with the thrombin Gly216 residue, and the adjacent P3 hydrophobic side chain which accounts for -4.1 kJ/mol improvements in the binding. With the second thrombin inhibitor series, we replaced the m-chlorobenzyl side chain with a benzamidine group, which is considered to be a more firmly bound group inside the S1 pocket. This substitution was done to investigate how the change from a loosely bound inhibitor to a more potent one can affect the cooperativity magnitude. However, we found that the magnitude of the cooperativity remained relatively unchanged with a -3.9 kJ/mol positive cooperativity. In chapter 3, we investigated how an additional hydrogen bond added to the ligand structure can affect the magnitude of the cooperativity. In order to do so, a series of thrombin inhibitors was designed wherein we added an additional H-bond to the ligand structure. We found that there is a significant improvement in the magnitude of positive cooperativity between the carbonyl group and the hydrophobic side chain ( -6.6 kJ/mol and -5.5 kJ/mol in the m-chlorobenzyl and benzamidine series, respectively). In chapter 4, we proceed further to evaluate the effect of the non-classical bioisosteric replacement of the carbonyl functionality with sulphonyl functionality on the cooperativity. The resulting positive cooperativity between the H-bonding group and hydrophobic side chains was greatly reduced. In chapter 5, we provide a complete SAR study of how the P2 hydrophobic side chain in the thrombin S2 pocket contributes to the ligand binding affinity. Chapter 6 is mainly focused on answering a unique question: Can different hydrophobic side chains reinforce each other through cooperativity. Also, we go further to reveal the effect of the proline ring rigidity on two different types of positive cooperativity between different ligand functional groups. The study in chapter 7 shows a very strong positive cooperativity ( -6.1 kJ/mol) between ligand carbonyl and amino groups, which make two strong H-bonds with the thrombin Gly216 residue. In addition, we reveal how the presence of a larger hydrophobic side chain in the S3 pocket will impact the magnitude of that cooperativity. Also, we proceed further to show how the manipulation of a H-bond ( -NH2 group) with different capping groups (i.e. acetyl, methylsulphonyl and others) will affect the magnitude of that cooperativity. The overall goal of the current work is to enhance the basic understanding of the complex process of molecular recognition. This would be done by obtaining a body of well-characterized data with closely related molecules on the single target thrombin so as to fully understand the cooperativity between ligand functional groups and, finally, provide a database for the incorporation of these newly defined affects into the computer algorithms to generate structure-based-design leads for any therapeutic target.
Author: Anthony Stone
Publisher: OUP Oxford
ISBN: 0191652954
Category : Science
Languages : en
Pages : 352
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Book Description
The theory of intermolecular forces has advanced very greatly in recent years. It has become possible to carry out accurate calculations of intermolecular forces for molecules of useful size, and to apply the results to important practical applications such as understanding protein structure and function, and predicting the structures of molecular crystals. The Theory of Intermolecular Forces sets out the mathematical techniques that are needed to describe and calculate intermolecular interactions and to handle the more elaborate mathematical models. It describes the methods that are used to calculate them, including recent developments in the use of density functional theory and symmetry-adapted perturbation theory. The use of higher-rank multipole moments to describe electrostatic interactions is explained in both Cartesian and spherical tensor formalism, and methods that avoid the multipole expansion are also discussed. Modern ab initio perturbation theory methods for the calculation of intermolecular interactions are discussed in detail, and methods for calculating properties of molecular clusters and condensed matter for comparison with experiment are surveyed.
Author: Philip Coppens
Publisher: International Union of Crystallography
ISBN: 0195098234
Category : Science
Languages : en
Pages : 373
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Book Description
This book deals with the electron density distribution in molecules and solids as obtained experimentally by X-ray diffraction. It is a comprehensive treatment of the methods involved, and the interpretation of the experimental results in terms of chemical bonding and intermolecular interactions. Inorganic and organic solids, as well as metals, are covered in the chapters dealing with specific systems. As a whole, this monograph is especially appealing because of its broad interface with numerous disciplines. Accurate X-ray diffraction intensities contain fundamental information on the charge distribution in crystals, which can be compared directly with theoretical results, and used to derive other physical properties, such as electrostatic moments, the electrostatic potential and lattice energies, which are accessible by spectroscopic and thermodynamic measurements. Consequently, the work will be of great interest to a broad range of crystallographers and physical scientists.
Author: Juan Novoa
Publisher: Royal Society of Chemistry
ISBN: 1782621733
Category : Science
Languages : en
Pages : 782
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Book Description
This new book brings together the latest information on intermolecular bonding within molecular crystals, providing a very useful introductory text for graduates.
Author: Atta-ur-Rahman
Publisher: Bentham Science Publishers
ISBN: 1681087472
Category : Science
Languages : en
Pages : 317
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Book Description
Advances in Organic Synthesis is a book series devoted to the latest advances in synthetic approaches towards challenging structures. The series presents comprehensive reviews written by eminent authorities on different synthetic approaches to selected target molecules and new methods developed to achieve specific synthetic transformations or optimal product yields. Advances in Organic Synthesis is essential for all organic chemists in academia and the industry who wish to keep abreast of rapid and important developments in the field. This volume presents the following reviews: o Recent Progress on Asymmetric Synthesis of Chiral Flavanones, Chromanones, and Chromenes o Supramolecular Chemistry of Modified Amino Acids and Short Peptides o The Use of Nanocatalysts in the Synthesis of Heterocycles: A Contemporary Approach o Synthesis and Applications of 1,2,3-Triazoles o Ring C–H Functionalization of Aromatic N-Oxides.
Author: Peter Day
Publisher: Royal Society of Chemistry
ISBN: 1847551394
Category : Science
Languages : en
Pages : 333
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Book Description
Traditionally, magnetic materials have been metals or, if inorganic compounds such as oxides, of continuous lattice type. However, in recent years chemists have synthesized increasing numbers of crystalline solids based on molecular building blocks in the form of coordination and organometallic complexes or purely organic molecules, which exhibit spontaneous magnetization. In striking contrast to conventional magnets, these materials are made from solutions close to room temperature rather than by metallurgical or ceramic methods. This book, which originates from contributions to a Discussion Meeting of The Royal Society of London, brings together many of the leading international practitioners in the field, who survey their own recent work and place it in the context of the wider fields of magnetism and supramolecular chemistry. All aspects of molecular-based magnets are addressed, including synthesis, structure-property relations and physical properties. Contents include details of the characterization of the first purely organic ferromagnet, the synthesis of high coercivity materials and a unique description of new materials with Curie temperatures well above ambient. A coherent survey of this rapidly developing field for the more general reader, Metal-Organic and Organic Molecular Magnets will also be welcomed by researchers and lecturers in materials science and inorganic or solid state chemistry.
