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  • 1
    Publikationsdatum: 2023-03-08
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in LeClerc, H., Tompsett, G., Paulsen, A., McKenna, A., Niles, S., Reddy, C., Nelson, R., Cheng, F., Teixeira, A., & Timko, M. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel. IScience, 25(9), (2022): 104916, https://doi.org/10.1016/j.isci.2022.104916.
    Beschreibung: Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed. Detailed product analysis revealed the importance of fatty-acid oligomerization during biocrude formation, highlighting the role of acid-base catalysts in promoting condensation reactions. Economic and environmental analysis found that the new technology has the potential to reduce US greenhouse gas emissions by 2.6% while producing renewable diesel with a minimum fuel selling price of $1.06/GGE. HAP can play a role in transforming food waste from a liability to a renewable fuel.
    Beschreibung: This work was funded by the DOE Bioenergy Technology Office (DE-EE0008513), a DOE DBIR (DE-SC0015784) and the MassCEC. The authors thank WenWen Yao, Department of Environmental Science at WPI, for TOC analysis, Mainstream Engineering for heating value characterization of the oil and solid samples, Wei Fan for assistance in obtaining SEM images and, Julia Martin and Ronald Grimm for their assistance in collecting XPS data, and Jeffrey R. Page for his assistance with oil upgrading and analysis. HOL was partially funded for this work by NSF Graduate Research Fellowship award number 2038257. A portion of this work was performed at the National High Magnetic Field Laboratory Ion Cyclotron Resonance user facility, which is supported by the NSF Division of Materials Research and Division of Chemistry through DMR 16-44779 and the State of Florida.
    Schlagwort(e): Chemistry ; Chemical engineering ; Catalysis
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 2
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Mineralogy includes thirteen chapters that discuss the methodology of specific mineralogical methods, the composition of minerals from different igneous rocks, and the composition of minerals from different sedimentary rocks.It contains detailed mineralogical studies from Africa, Asia, and Europe. Chapters present different scientific mineralogical methods and detailed descriptions of minerals from different magmatic and sedimentary rocks.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNV Chemistry of minerals, crystals and gems
    Sprache: Englisch
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  • 3
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Benzimidazole is a comprehensive survey of the known and new methods of benzimidazole synthesis, the spectral and theoretical aspects of existing benzimidazole derivatives, and the anticancer properties of a new class of benzimidazole derivatives. This book examines aspects and newer mechanisms of benzimidazoles containing heterocyclic moiety. Chapters report on anticancer properties of benzimidazole derivatives, novel methods of synthesis of benzimidazoles, versatile nature of the benzimidazoles, spectral and theoretical studies of benzimidazole derivatives, and medicinal importance and pharmacological aspects of benzimidazole derivatives.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Sprache: Englisch
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  • 4
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Green Chemistry - New Perspectives is at the frontiers of this continuously evolving interdisciplinary science, and publishes research that attempts to reduce the environmental impact of the chemical enterprise by developing a technology base that is inherently non-toxic to living things and the environment. The book covers all aspects of green chemistry, including chemical synthesis, nano synthesis, eco-friendly processes, biomass, extraction techniques, environmental remediation, and energy, making it a unique reference resource. This will continue to encourage scientists around the world to develop novel synthetic methods or improve the existing ones to circumvent some of the problems and favours all aspects of green chemistry. This book is intended for academia, professionals, scientists, as well as graduate and undergraduate students without any geographical limitations.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Sprache: Englisch
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  • 5
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: This book consists of several selected chapters on important subjects in modern high-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC). The content addresses aspects related to both improvements in the mainstream HPLC/UPLC technology and utilization, as well as developments of exploratory new materials and equipment. The book presents useful details about the presented subjects as well as describes new applications and/or relevant case studies for each subject. It is addressed to a large audience of analytical chemists involved in separation science. Each chapter is authored by scientists with considerable field and academic experience.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Sprache: Englisch
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  • 6
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Recent Advances in Chemical Kinetics provides a comprehensive overview of several types of chemical reactions. It includes six chapters that discuss solvent catalysis, customized flow reactors, p-conjugation in kinetics, kinetics of autoxidation, molecular chameleon for cations and anions, and internal clocks of atoms.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry
    Sprache: Englisch
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  • 7
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Redox reactions are involved in biochemistry, energy, corrosion, and much more. In both biology and electrochemistry, the redox reaction is complex and varied. For example, redox shuttles in supercapacitors show aspects of molecular electrochemistry applied to electrode porosity. In pseudocapacitors, the formalism associated with their electrochemical response requires investigation and formalism. Similarly, the simple definition of redox potential opens fundamental questions about its measurement in solutions without supporting salts. This book illustrates the variety of redox reactions in its examination of the importance of redox molecules in the development of new electrical energy storage devices.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRH Electrochemistry and magnetochemistry
    Sprache: Englisch
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  • 8
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: We are living in a critical time, both for humanity and the planet, which has led us to look for more sustainable formulas to interact with the environment. One of the important changes in the design and operation of chemical processes is the search for environmentally friendly technologies. Supercritical carbon dioxide has been revealed as a promising environmentally friendly solvent that is energy efficient, selective and capable of reducing waste, making it a promising alternative to conventional organic solvents. However, reliable and versatile mathematical models of phase equilibrium thermodynamics are needed for the use of supercritical carbon dioxide in process design and viability studies. This book reviews experimental procedures for obtaining high-pressure phase equilibria data and describes the phase diagrams of binary mixtures and some thermodynamic models capable of determining the conditions of phase equilibria at high pressures. These concepts are applied to the components of the transesterification reaction of rac-2-pentanol with a vinyl ester, which is important in the pharmaceutical industry because (S)-2-pentanol can be obtained as a reaction product. This product is a key intermediate in the synthesis of drugs against Alzheimer’s disease.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry
    Sprache: Englisch
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  • 9
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: In recent decades, artificial porous structures have attracted increasing enthusiasm from researchers inspired by the fascinating molecular pores in nature and their unique biological functions. Although substantial achievements in porous materials have been realized, the construction of topologically designed pores is still challenging. Recently, the emergence of covalent organic frameworks (COFs), which are constructed based on organic and polymer chemistry, has made it possible to design artificial pores with controlled pore size, topology and interface properties. COFs are crystalline porous materials constructed by the precise reticulation of organic building blocks via dynamic covalent bonds. Distinct from non-covalent interactions which tend to produce isostructures, covalent bonds enable accurate pore design owing to their predetermined reaction pathways. In addition, the appropriate polycondensation of organic building units enables the formation of extended two-dimensional (2D) and three-dimensional (3D) polymer architectures with periodically ordered skeletons and well-defined pores. With their large surface area, tailorable structures, and tunable chemistry, COFs are regarded as potentially superior candidates for various applications including catalysis, energy storage and conversion, mass transport and biotechnology. This book examines the historic achievement of COFs, providing clear and comprehensive guidance for researchers on their structural design, synthetic protocols and functional exploration.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Sprache: Englisch
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  • 10
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Fluoride covers a continuum of topics that are frequently studied in the broad area of fluoride (F) research. It provides an overview of the primary sources of environmental fluoride in typical high-fluoride environments and demonstrates the transitions and transformations that emerge and culminate in hydro-geochemical interactions that result in fluoride-fouling of large portions of the world’s water and agricultural resources. This way, the book pinpoints the connection between F enrichment of water sources and the prevalence of endemic fluorosis in certain areas of the world. In order to contribute to a better understanding of the global fluoride problem, new fluoride detection and quantification technologies are proposed with an in-depth analysis of emerging trends in the use of portable user-friendly devices in point-of-use measurements of water fluoride. This has been presented against the backdrop of a robust overview of traditional fluoride quantification methodologies that are still in wide application among the scientific communities. In addressing fluoride toxicities, which are not limited to dental and skeletal dilapidations, the authors have explored the role of natural antioxidants in ameliorating physiological fluoride-induced noxious effects in mammalian systems. Nonetheless, since community dependence on high-fluoride water due to a lack of alternative clean water sources remains to be the principal pathway of human fluoride over-exposure, a review chapter on F mitigation techniques applied all over the world is incorporated aiming at providing a succinct overview of water defluoridation techniques and strategies being used to combat the impacts of human F overexposure around the globe. Since every cloud has a silvery lining, the possibility of using ammonium fluorides as a novel reagent in mineral processing has been considered convenient industrial fluorinating agents, which present the possibility of complete regeneration that is not afforded by the reagents presently used in decomposing silicon component of the ores.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNK Inorganic chemistry
    Sprache: Englisch
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  • 11
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: This book discusses the chemistry and applications of pyridine derivatives. The library of pyridine derivatives is growing steadily with numerous synthetic analogues already described and the identification of new, naturally occurring pyridine-based compounds. The book includes ten chapters organized into two parts. The first part focuses on the numerous types of reactions that arise from pyridine derivatives. The second part examines the pharmaceutical applications of pyridine derivatives as well as their usefulness as sensors for metal cations and extracting agents for platinum group metals.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Sprache: Englisch
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  • 12
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: The book discusses multiple issues associated with modern dosimetry in physics and treatment planning and how investigators from diverse world centers and institutions approach problem-solving in these important areas. It examines topics including pretreatment validation and factors affecting reference dosimetry. It also addresses unique issues affecting pediatric populations as well as the modern role of thermoluminescence validation. Several chapters discuss intensity modulation, including defining modern problems associated with both treatment planning and the definition of tumor and normal tissue contours. Furthermore, the book examines the role of imaging as both a vehicle to define tumor targets and normal tissue as well as a tool for dose validation.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRL Nuclear chemistry, photochemistry and radiation
    Sprache: Englisch
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  • 13
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: The book comprises 14 chapters covering all the issues related to water desalination. These chapters emphasize the relationship between problems encountered with the use of feed water, the processes developed to address them, the operation of the required plants and solutions actually implemented. This compendium will assist designers, engineers and investigators to select the process and plant configuration that are most appropriate for the particular feed water to be used, for the geographic region considered, as well as for the characteristics required of the treated water produced. This survey offers a comprehensive, hierarchical and logical assessment of the entire desalination industry. It starts with the worldwide scarcity of water and energy, continues with the thermal - and membrane-based processes and, finally, presents the design and operation of large and small desalination plants. As such, it covers all the scientific, technological and economical aspects of this critical industry, not disregarding its environmental and social points of view. One of InTech's books has received widespread praise across a number of key publications. Desalination, Trends and Technologies (Ed. Schorr, M. 2011) has been reviewed in Corrosion Engineering, Science & Technology – the official magazine for the Institute of Materials, Minerals & Mining, and Taylor & Francis's Desalination Publications. Praised for its “multi-faceted content [which] contributes to enrich it,” and described as “an essential companion...[that] enables the reader to gain a deeper understanding of the desalination industry,” this book is testament to the quality improvements we have been striving towards over the last twelve months.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Sprache: Englisch
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  • 14
    Publikationsdatum: 2024-04-05
    Beschreibung: The Global Methane Initiative (GMI) is a voluntary international partnership that promotes methane recovery and reuse activities in developing and transition economies. The U.S. Department of State requested an evaluation of the activities and outcomes supported in whole or in part by its contributions to GMI to gauge its value added to the program.
    Schlagwort(e): Physics ; Environmental Science ; Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TQ Environmental science, engineering and technology ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBP Meteorology and climatology
    Sprache: Englisch
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  • 15
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Progress in agricultural, biomedical and industrial applications' is a compilation of recent advances and developments in gas chromatography and its applications. The chapters cover various aspects of applications ranging from basic biological, biomedical applications to industrial applications. Book chapters analyze new developments in chromatographic columns, microextraction techniques, derivatisation techniques and pyrolysis techniques. The book also includes several aspects of basic chromatography techniques and is suitable for both young and advanced chromatographers. It includes some new developments in chromatography such as multidimensional chromatography, inverse chromatography and some discussions on two-dimensional chromatography. The topics covered include analysis of volatiles, toxicants, indoor air, petroleum hydrocarbons, organometallic compounds and natural products. The chapters were written by experts from various fields and clearly assisted by simple diagrams and tables. This book is highly recommended for chemists as well as non-chemists working in gas chromatography.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Sprache: Englisch
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  • 16
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: This book discusses electrocatalysis and electrocatalysts for energy, water electrolysis, water treatment, CO2 conversion, and green chemistry. It reviews various electrocatalysts and their properties and electrochemical performances. The first section of the book covers topics in direct alcohol fuel cells including Pt-based electrocatalysts as non-carbon electrode support materials and the development of electrocatalysts for direct methanol fuel cells. The second section of the book covers various topics in electrocatalysis and electrocatalysts for a cleaner environment, including electrocatalysts for the conversion of CO2 to valuable products and SYNGAS, electrocatalysts for water electrolysis, and much more.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRH Electrochemistry and magnetochemistry
    Sprache: Englisch
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  • 17
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publikationsdatum: 2023-06-23
    Beschreibung: The aim of this second Eng Special Issue is to collect experimental and theoretical re-search relating to engineering science and technology. The general topics of Eng are as follows: electrical, electronic and information engineering; chemical and materials engineering; energy engineering; mechanical and automotive engineering; industrial and manufacturing engineering; civil and structural engineering; aerospace engineering; biomedical engineering; geotechnical engineering and engineering geology; and ocean and environmental engineering. Therefore, the following editorial is a selection of representative works of these topics.
    Schlagwort(e): &nbsp ; Environment Management ; Environmental Engineering ; Chemical Engineering ; Materials Engineering&nbsp ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues::TBX History of engineering & technology
    Sprache: Englisch
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  • 18
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Surfactants are ubiquitous and have applications in diverse areas, including food, cosmetics, detergents, lubricants, enhanced oil recovery (EOR), and targeted drug delivery systems. Their wide diversity of applications owes to their unique structure, namely, a hydrophilic and a hydrophobic group present in the same molecule. Although most surfactants used industrially are synthetic, there is a growing need for natural surfactants, as the latter is obtainable from renewable sources and are less toxic and highly biodegradable in contrast to their synthetic counterparts. This book is a compilation of interesting articles by various experts that cover various applications of both synthetic and natural surfactants.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRC Colloid chemistry
    Sprache: Englisch
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  • 19
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: The chemical sensor plays an essential role in the fields of environmental conservation and monitoring, disaster and disease prevention, and industrial analysis. A typical chemical sensor is a device that transforms chemical information in a selective and reversible way, ranging from the concentration of a specific sample component to total composition analysis, into an analytically useful signal. Much research work has been performed to achieve a chemical sensor with such excellent qualities as quick response, low cost, small size, superior sensitivity, good reversibility and selectivity, and excellent detection limit. This book introduces the latest advances on chemical sensors. It consists of 15 chapters composed by the researchers active in the field of chemical sensors, and is divided into 5 sections according to the classification following the principles of signal transducer. This collection of up-to-date information and the latest research progress on chemical sensor will provide valuable references and learning materials for all those working in the field of chemical sensors.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Sprache: Englisch
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  • 20
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Distillation is an important separation technique that has been used for many centuries to exploit the volatility differences between components in a mixture. The distillation process has many variations and applications. This book includes two sections on desalination and reactive distillation. It discusses desalination in the processes of solar and membrane distillation, with a focus on the reduction of energy costs to obtain potable water. It also discusses reactive distillation, which can be used in some cases to reduce the power duty in the separation process by using the reaction heat directly in the separation. The book includes cases of mathematical modeling, simulation, and optimization of the distillation process.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Sprache: Englisch
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  • 21
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Cyclodextrins (CDs) have attracted great interest from the research community as well as industries in an array of sectors because of their unique structural features. This book provides a comprehensive overview of CDs, beginning with their historical background. Chapters address such topics as the structure and physiochemical properties of CDs, advancements in the field, and potential applications of these materials in fields such as drug delivery and sensing. This book reveals new frontiers in the CD world and is a useful resource for organic, analytical, and supramolecular chemists as well as scientists engaged in biological and material sciences.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Sprache: Englisch
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  • 22
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: The book presents a comprehensive overview of sorption, which is a multi-parametric separation process. It is extensively used in the removal of various pollutants from the tertiary stage of wastewater treatment, from leachates, etc. It discusses fundamental points of the technique as well as kinetic theories and isotherms. It also examines the synthesis and characterizations of all studied adsorbent materials to find their paths of sorption. Finally, it highlights the importance of having a cost-estimation plan for the synthesis of sorbent materials as well as predictions for their reusability.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRX Surface chemistry and adsorption
    Sprache: Englisch
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  • 23
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Carotenoids are natural and versatile secondary metabolites, most of them showing colours that vary from yellow to red. They are widespread among living beings where they are involved in many biological roles reporting beneficial actions. To date, more than 750 carotenoids have been described in nature. Humans cannot synthesize carotenoids de novo, thus they are mainly obtained through diet. In fact, carotenoids are consistently found in tissues or biological fluids where they play a beneficial decreasing the risk of developing some diseases.During the last half-century, significant advances in carotenoids research have been made. This book highlights new perspectives and applications of carotenoids including characterization and isolation of new compounds (including rare carotenoids), their production at a mid-large scale (involving new innovative approaches), and uses of carotenoids in different biotechnological fields like food science, biomedicine, and cosmetics.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Sprache: Englisch
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  • 24
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    IntechOpen | IntechOpen
    Publikationsdatum: 2024-04-05
    Beschreibung: Infrared Spectroscopy - Perspectives and Applications is a compendium of contributions from experts in the field of infrared (IR) spectroscopy. This assembly of investigations and reviews provides a comprehensive overview of the fundamentals as well as the groundbreaking applications in the field. Chapters discuss IR spectroscopy applications in the food and biomedicine sectors and for measuring transport through polymer membranes, characterizing lignocellulosic biomasses, detecting adulterants, and characterizing enamel surface advancements. This book is an invaluable resource and reference for students, researchers, and other interested readers.
    Schlagwort(e): Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry::PNFS Spectrum analysis, spectrochemistry, mass spectrometry
    Sprache: Englisch
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 23 (1977), S. 13-17 
    ISSN: 1432-0827
    Schlagwort(e): Dental calculus ; Glycopeptide ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary A method is described for the isolation and purification of a sulphated glycopeptide from human supragingival calculus. The compound was isolated after using EDTA treatment, 2 M CaCl2 extraction, proteolytic digestion, ethanol precipitation, and finally purified by DEAE cellulose chromatography. It migrated as a single component on cellulose acetate electrophoresis, and chemical and infrared spectral analysis showed the presence of covalently attached sulphate groups. The sulphated glycopeptide was distinguished from being a sulphated glycosaminoglycan.
    Materialart: Digitale Medien
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 23 (1977), S. 39-44 
    ISSN: 1432-0827
    Schlagwort(e): Dental cementum ; Collagen ; Protein ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary Cyanogen bromide (CNBr) peptides were prepared of the insoluble collagen of bovine dental cementum. Following chromatographic separation, the peptides were identified by their amino-acid composition. Type I collagen ([α1(I)]2α2) accounted for more than 90% of the organic matrix, while Type III collagen ([α1(III)]3) was present at a level of approximately 5%. Amino-acid analyses revealed that the CNBr peptides from α1(I) and α2 chains of cementum closely resembled the corresponding peptides from calf skin. The only systematic difference was a higher level of hydroxylation of prolyl and lysyl residues of the cementum peptides.
    Materialart: Digitale Medien
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Calcified tissue international 23 (1977), S. 87-94 
    ISSN: 1432-0827
    Schlagwort(e): Calcium ; Osteoporosis ; Lactation ; Chemistry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin , Physik
    Notizen: Summary The calcium homeostatic mechanism was challenged in adult female rats by feeding them a calcium-deficient diet containing oxalate, and by subjecting them to pregnancy and lactation. The regimen caused a substantial weight loss, especially in those animals which reared their young well. Severe hypocalcaemia was observed in the lactating rats. Serum-P was slightly elevated. The content of hydroxyproline in serum was considerably elevated, reflecting the degree of calcium deprivation. Serum proteins were least influenced. The calcium depriving regimen reduced the growth of long bones, but did not stop it. The ash content of the bones was considerably reduced, the degree of reduction depended on the degree of calcium deprivation. Ash as percentage of total bone organ was reduced, but not to the same extent as total ash. Analyses of different parts of femur showed that the proximal and distal parts had lost more bone mineral than the diaphyseal shaft. The ash content of cortical bone tissue from the femur was estimated by a volumetric method. No differences were observed between test groups and controls, indicating that no measurable amounts of bone mineral had been removed from the walls of the vascular canals or by osteocytic osteolysis. Planimetric determinations on cross sections from femora disclosed that a great amount of bone had been removed from the endosteal surface of the diaphysis, while the periosteal surface demonstrated reduced bone apposition.
    Materialart: Digitale Medien
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Environmental biology of fishes 2 (1977), S. 241-259 
    ISSN: 1573-5133
    Schlagwort(e): Production ; Fisheries ; Population dynamics ; Energetics ; Fishes ; Competition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis Production rates of seven species of fishes were determined for one year in a 0.95 ha pond. Total annual production of all fishes in the pond was 209 g m−2y−1 (after the subtraction of 16.2 g m−2y−1 of negative production). Over 90% of the production occurred in the months of June through September, with young-of-the-year fishes contributing 84% of the total. When Y of Y fishes shifted to benthic diets in the spring, the small biomass of benthos available could not sustain the large biomas of fish. Severe competition for the available food then resulted in decreased production rates for the entire fish taxocene.
    Materialart: Digitale Medien
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  • 29
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 67-80 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence on the excess scattering function P(μ) of flutuations in the electron density ρ within a macromolecule is treated, to the approximation that the solvent is a structureless medium of constant electron density ρ0. The results for P(μ) and the apparent value of the mean square radius Rapp2, can be expressed as functions of the excess electron density Δρ: P(μ) = X(μ) + (Δρ)-1Y(μ) + (Δρ)-2Z(μ) and Rapp2 = Rx2 + (Δρ)-1Ry2 + (Δρ)-2Rz2, where X(μ) and Rx2 depend only on the shape of the macromolecule, while Y(μ) and Ry2 as well as Z(μ) and Rz2 depend on the shape and the fluctuations in ρ. By varying the electron density of the solvent, the contributions of the shape and the internal structure of the macromolecule can be resolved. The quantities Rx2, Ry2, and Rz2 are evaluated for seven models to illustrate the relative importance of these contributions for representative structures.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 30
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 121-142 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chiroptical properties of the cyclic dipeptides cyclo (L-alanyl-L-tyrosine) and cyclo(L-tyrosyl-L-tyrosine) have been investigated as a function of molecular conformation. Theoretical optical calculations and conformational energy calculations have been carried out as a function of the side-chain dihedral angles χ1 and χ2, and as a function of the angle of fold of the cyclic dipeptide backbone. The results of these theoretical calculations have been compared with experimental circular dichroism (CD) data. Theoretical predictions are in very good agreement with experiment for c(L-Tyr-L-Tyr). Agreement was not quite as good for c(L-Ala-L-Tyr), although the signs of all of the Cotton effects were apparently predicted correctly except for that associated with the lowest energy tyrosine absorption band.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
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  • 31
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 289-298 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The slow kinetics of annealing processes in multistranded nucleic acids is spectrophotometrically investigated using poly(A)·2poly(U) as a model system. The absorbance changes at specific wavelengths show that double-helical (A·U) base pairs appear as transient intermediates. The annealing process is identified by the enlargement of triple-helical sequences at the cost of (A·U) base pairs and unpaired (U) residues. A large time range in the reorganization of mismatched chain configurations is characterized by a logarithmic dependence on time. This observation is quantitatively described by a kinetic model developed by Jackson. In Jackson's model the rate-limiting process in the slow annealing phase of maximizing triple-helical sequences, is the removal of strand entanglements, knots, and hairpin loops by complete unwinding of those helical stretches which stabilize the mismatched configurations. The results of the present study are briefly discussed in terms of optimum conditions for hybridization experiments and for the preparation of polynucleotide complexes commonly used to produce interferons.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 32
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 341-368 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of anions of neutral salts on the fluorescence emission of six proteins as well as on tryptophan and tyrosine were studied in relation to the structure of proteins. Most anions are good quenchers of tryptophyl and tyrosyl fluorescence, free or in proteins. The results with tryptophan and tyrosine indicate involvement of a collisional quenching mechanism due to agreement with Stern-Volmer law. The deactivation of fluorescence probably occurs because of the transition from singlet state to triplet state. Lehrer's modification of Stern-Volmer law was applied to proteins. The effective quenching constants ([KQ]eff) and the fraction of fluorescence available ([fa]eff) to the quencher are also calculated.In contrast to its effect on tryptophan, CH3COO- quenches tyrosyl fluorescence and ClO4- does not. The effects on fluorescence of ribonuclease and free tyrosine are similar and without any changes in emission maximum. The anions are divided into three groups based on the effect they have on tryptophan-containing proteins. (1) NO3-, NO2-, Br-, and I- have high [KQ]eff values and readily quench tryptophyl fluorescence of proteins causing a shift of emission maximum to a shorter wavelength. This change is due to the specific quenching of “exposed” tryptophan residues which are accessible to quenchers and the observed residual fluorescence is from the “buried” tryptophyls. (2) ClO4- and SCN- also quench fluorescence of tryptophan in proteins and have lower ([KQ]eff) values. In their presence the fluorescence maximum is shifted to a longer wavelength, which indicates the unfolding of a protein with [(fa)eff] = 1. (3) Cl-, CH3COO-, and SO4— do not have a direct effect on the fluorescence of tryptophan. Besides the “direct” effects, “indirect” effects on fluorophors in protein are also seen, pointing out that the neutral salts can interact in more than one manner with proteins. The effectiveness of anions in quenching fluorescence of proteins follows similar sequences which almost resemble the Hofmeister series, viz., SO4=, CH3COO- ≃ Cl- 〈 ClO4- 〈 SCN- 〈 Br- 〈 I- 〈 NO3- 〈 NO2-.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 33
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence of pH upon CD spectra of H-Trp-Trp-OH, H-Trp-Trp-Gly-OH, and H-Gly-Trp-Trp-OH is investigated and data are compared with those obtained for peptides containing only one tryptophyl residue. A negative Cotton effect at around 225 nm, which in previous work has been related to an increase of the conformational rigidity in compounds having the sequence -CO-Trp-Trp, is also observed in the case of H-Trp-Trp-OH and H-Trp-Trp-Gly-OH upon deprotonation of the terminal α-amino group. These data, together with observations arising from solvent and temperature effects, give evidence that H-Trp-Trp-OH undergoes a conformational change upon going from acid to alkaline conditions, where the two aromatic side chains become conformationally more rigid relative to each other. This rigidity generates an exciton coupling between the Bb transitions of the two indoles. Hydrophobic forces, including stacking interactions, do not appear important in stabilizing this conformationally rigid structure. Rather, intramolecular electrostatic interactions (e.g., hydrogen bondings or polar interactions between the aromatic side chain and the peptide backbone) as well as interactions with the OH group(s) of the solvent, are suggested to be the salient forces. Possible structures which obey these requisites are discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 34
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 427-435 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The fine structure of the thermal denaturation of viral DNA's was analyzed with the spectral method established by Felsenfeld and Hirschman, and Fresco et al. A fully automated system measuring melting curves at four wavelengths at the same time was developed for this purpose. With this device, (G + C)-contents of melting components of λ DNA's were determined. The correlation between the (G + C)-content and the melting temperature of each melting component is found to be well described by the linear relationship given by Marmur and Doty. The denaturation of each component is regarded as cooperative. The Marmur-Doty relation also stands for the local denaturation of T2 DNA, which has a narrow melting range.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 35
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 461-464 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 36
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have constructed an apparatus for the simultaneous measurement of electrophoretic mobility, μ, and diffusion coefficient, D, of macromolecules and cells. It combines band electrophoresis in a vertical, sucrose-gradient stabilized column, with quasielastic laser light-scattering determination of the diffusion coefficient of the species within the band. The entire electrophoresis cell is scanned through the laser beam of the quasielastic laser light-scattering apparatus by a vertical translation stage. Total intensity light-scattering measurement at each point in the cell gives the macromolecular concentration at that point. Solvent viscosity and electrical potential are measured at each point in the cell. Application of this apparatus to resealed red blood cell ghosts and to bovine hemoglobin indicates that measurements of field, viscosity, and migration distance are reliable, and that electroosmosis is insignificant. Application to T4D bacteriophage gives μ20,w = (-1.05 ± 0.05) × 10-4 cm2/V sec and D20,w = (3.35 ± 0.10) × 10-8 cm2/sec for fiberless particles, and μ20,w = -(0.59 ± 0.03) × 10-4 cm2/V sec and D20,w = (2.86 ± 0.09) × 10-8 cm2/sec for whole phage with 6 fibers. Approximate analysis of these results with the Henry electrophoresis theory for spheres in dicates that each fiber contributes about 193 positive charges to the phage particle, compared with 327 from amino-acid analysis. The advantages and disadvantages of this apparatus, relative to conventional electrophoresis and to electrophoretic light scattering, are discussed.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 37
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(His-Ala-Glu) and poly(Lys-Ala-Glu) were examined by viscosity and potentiometric titration. These measurements were interpreted in terms of the hydrodynamic size of the above sequential polypeptides. Effects of polymer, size and concentration, and solution-salt concentration were demonstrated. Although the sequential polypeptides generally behave like polyampholytes, they do demonstrate some differences. These differences my be attributed to the ability of ionized side chains three residues apart to repel themselves, in the order His 〈 Glu 〈 Lys.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 38
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Proton magnetic resonance spectra of model dipeptide molecules R1-C′1O1-N2H2-C2αH2αR2-C′2O2-N3H3-R3 in CCl4 solutions exhibit splited signals when investigating on mixtures of L and D enantiomers differing from the racemic composition. The major effect is observed on amide proton signals which are the ones most sensitive to the ratio of aggregation. The stereoselective dimerization of enantiomeric molecules in the so-called C5 conformational state is shown to be responsible for such a phenomenon, the intensity of which depends on the bulkiness of the side chain R2. A theoretical approach is proposed which gives predictions in close agreement with our own experimental findings.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1725-1733 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The depolarization thermal current method is applied to the study of the polarization phenomena in the keratin-water system. Three depolarization thermal current peaks have been evidenced in hair keratin. This paper deals with the detailed study of peak II. For the first time, the mechanism responsible for this peak is ascribed to molecular reorientation. The effect of water upon the characteristics of peak II is also described, and an activation energy of 8.4 kcal/mol is computed. These results, in connection with other studies, lead us to interpret peak II as due to the reorientation in the bound or intermediate water molecules. The effect of copper confirms that the carboxyl groups are hydration sites.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 40
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1735-1745 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Infrared spectroscopy was used for the determination of the base-pairing content of four specific tRNAs in deuterium oxide solution. Infrared spectra were obtained in the 1750-1550 cm-1 region at various temperatures ranging from about 15 to 90°C. Melting curves were constructed by plotting the molar extinction coefficient at ν = 1657 cm-1 versus temperature. These transition curves enabled us to determine the ranges of temperature which correspond to the ordered (partially double-stranded) or randomly coiled structure of the tRNA. For a set of wavenumbers the extinction coefficients at these temperatures were used for the calculation of the base-pairing content. The procedure employed here is based on a method described earlier by Thomas [(1969) Biopolymers 7, 325-334]. For the conditions selected for this investigation (Mg2+-free D2O-buffer; 0.01M tris-DCl, 0.015M NaCl, pD 7.5) the results of this determination agree within the limits of errors with the number of base pairs predicted by the cloverleaf model.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1779-1793 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have calculated the translational and rotational frictional coefficients of structures related to T2 and T4 bacteriophage, using the theoretical framework developed in the preceding two papers. The structures considered were models for tail-fiberless phage, and for whole phage with fibers in the extended and retracted portions. We also computed and compared with the experiment the changes in translational frictional coefficient produced by successive addition of 1-6 fibers to the fiberless particle. Agreement with experimental results is markedly improved over previous theoretical efforts, especially with respect to the effect of tail-fiber extension. Some significant discrepancies remain, however, in the comparison of fiber-retracted and fiberless phage.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1765-1778 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have used the modified Oseen hydrodynamic interaction tensor along with iterative numerical solution of the coupled hydrodynamic interaction equations to calculate the rotational diffusion coefficients of macromolecular complexes composed of nonidentical spherical subunits. For the one structure, a prolate ellipsoid of revolution, for which exact solutions are available, a subunit model with the same length and volume gives asymptotic agreement with the Perrin equations. Other structures considered include plane polygonal rings, lollipops, and dumbbells.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 43
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 44
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have studied the effects of temperature, EDTA, and ionic strength on C-polysaccharides in solution by examining the details of the time-correlation function using a 96-channel single-clipped photon correlation spectrometer. Our linewidth results have shown that the C-polysaccharides in buffer solution form aggregates of very broad distributions. Thus, fractionation by gel-filtration chromatography is only mildly effective. Although the aggregate sizes seem to remain relatively constant from 4 to 25°C, a fraction of those aggregates break up to form smaller fragments or monomers at higher temperatures. However, the dissolution-association process is quite slow and takes days even at room temperatures before the equilibrium is reached. We have also shown that by adding an excess amoutn of EDTA, the aggregates can be broken up. Again the dramatic changes occur only at short delay times suggesting that a protion of the larger aggregates remains. Finally, the amount and size of aggregates depend upon the ionic strength which exhibit a maximum ΓT/sin2 (θ/2) around 0.1-0.2 M KCl.If the activities of polysaccharides in solution depend upon molecular size, the standard techniques such as gel-permeation chromatography and ultracentrifugation cannot properly characterize the detailed size distribution. Quasielastic laser light scattering can provide us with a qualitative model. The quantitative details must necessarily await more extensive investigations using a combination of the techniques and better fractionation procedures in an appropriate buffer solution.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 45
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1033-1052 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The coupling of N-acyl-α-amino-acids with α-hydroxyacid-methyl amides results in depsipeptide molecules containing two chiral centers and one ester function inserted between two amide functions. Their conformational features have been investigated by IR spectroscopy, proton magnetic resonance, X-ray diffraction, and theoretical P.C.I.L.O. calculations.It is shown that most of these molecules are folded by an intramolecular 4 → 1 hydrogen bonding. Two folded conformations, similar to the well known β turn in peptides, are described, the stability of which depends on the configurational sequence in the investigated molecule.LL and LD species are folded in two different ways whereas LG sequences containing an achiral hydroxy-acid residue accommodate both of them. The presence of a N-terminal achiral amino acid noticeably decreases the folding ratio.The above conclusions are then compared with the conformational features of homologous tripeptide molecules.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 46
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1153-1158 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 47
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2105-2111 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of complex formation between fluorescein mercuric acetate and heat-denatured DNA were studied by measuring the fluorescence quenching of this reagent. This quenching process involved no immeasurably rapid phase and it was shown that this reaction follows simple second-order kinetics. The rate constant at 25°C was estimated to be 2.9 × 104M-1 sec-1 for calf-thymus DNA (42% G + C) and 1.1 × 104M-1 sec-1 for Micrococcus lysodeikticus DNA (72% G + C). Activation parameters for this reaction were calculated from the temperature dependence of the reaction rate, and the activation entropy was found to be highly negative (-27.5 cal/mol deg for calf-thymus DNA and -25.5 cal/mol deg for M. lysodeikticus DNA). The binding of fluorescein mercuric acetate to native DNA, which requires the opening of the double-helical structure, was also followed by measuring the absorbance change of this reagent. There was a lag phase in this binding process, and the enthalpy change for the opening step corresponded roughly to that for the opening of one base pair. These findings are discussed in relation to the results of a similar study with formaldehyde.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 48
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The formation of collagen fibrils from soluble monomers and aggregates by thermal gelation at neutral pH can be divided into two distinct stages: a nucleation phase and a growth phase. Turbidity studies of the kinetics of the precipitation reaction show that the lag-phase time or nucleation reaction time, t′l, is markedly temperature dependent while the growth reaction time is temperature independent. The activation energy of the nucleation reaction is essentially constant over the temperature range studied. In monitoring the nucleation-phase reaction by various physicochemical techniques, including viscosity, sedimentation equilibrium, and light scattering, no evidence for the formation of aggregates was observed. Enrichment of the initial collagen solution with aggregates accelerates nucleation, but de novo nuclei formation is still required even in highly aggregated collagen preparations. Removal of pepsin and pronase susceptible peptides lengthens the nucleation reaction time and increases the sensitivity of the rate of nuclei formation to changes in ionic strength. Electron microscope studies show the fibrils formed from the protease-treated collagen to be less well organized. With pepsin-treated collagen, subfibrils and obliquely striated fibrils are seen, showing that while microfibrils are formed interactions between them are modulated by the enzyme susceptible peptides in the same way that these regions modulate nuclei assembly. It appears that pepsin and pronase susceptible peptide regions of collagen play a more prominent role in the in vitro assembly of collagen molecules to form D-stagger nuclei and fibrils than do ionic interactions between helical molecular regions. A mechanism of nucleation of collagen fibrillogenesis is discussed.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2243-2264 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Circular dichroism spectra of the nucleic acid monomers have been measured in aqueous solution and extended into the vacuum ultraviolet region to about 166 nm. Measurements were made on ribo and deoxyribo derivatives of adenine, guanine, hypoxanthine, cytosine, thymine, and uracil derivatives both with and without the 5′-phosphate (with the exception of ribosyl thymine 5′-phosphate). Absorption spectra of the deoxyribonucleotides measured to about 175 nm are also presented. The results demonstrate that both the circular dichroism and absorption spectra observed below 200 nm are no more complicated than the spectra normally recorded above 200 nm. In most cases, the circular dichroism spectra of the various derivatives of a given base are similar, indicating that the conformations are similar. On the other hand, the differences among the circular dichroism spectra of the various derivatives of a given base are sufficient to identify a particular derivative. The average circular dichroism for the deoxyribonucleotides is compared with the circular dichroism of native E. coli DNA. The comparison reveals that the circular dichroism of DNA below 200 nm is due principally to the interaction between the bases rather than the intrinsic circular dichroism of the monomers. The monomer transitions are discussed in relationship to the absorption and circular dichroism spectra presented.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 50
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2281-2298 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theory for the determination of DNA arrangements in DNA-containing specimens, using planar aromatic dye molecules as probes for plane polarization of fluorescence, has been described. At low dye-to-DNA concentrations, the dye molecules are sandwiched between the stacked bases of DNA; hence, the fluorescence from the dye bound to a local region of DNA helix is plane-polarized with the polarization direction perpendicular to the local axis of DNA. The degree of such polarization from an aligned DNA-specimen complexed with dye is determined both by the DNA orientation and the conformational state (e.g., base tilt) of DNA into that specimen. Analysis has been made of the relationship between the degree of polarization and the orientation of the emitting dipoles of dye. The dye complexes may be aligned in a mechanical shear or electric field. However, any change in the orientation distribution of the emitting dipoles due to force fields should be taken into account. With some assumptions and approximations, the magnitude and the direction of maximum polarization can be related to different orders of DNA coiling and to their various combinations. Since the measured polarization is averaged over all DNA regions of the specimen, if the magnitude of polarization is appreciable and the polarization occurs in the specific direction of the specimen, the theory helps to eliminate several probable arrangements of DNA. The predominant molecular features of the actual DNA arrangement can be determined through this process of elimination, as explained in two subsequent papers with T-even bacteriophage and chromosome systems.
    Zusätzliches Material: 5 Ill.
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  • 51
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 52
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Fluorescence of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) was enhanced in the presence of maltooligosaccharides, amylose, and other α-glucans. The dependence of relative TNS fluorescence intensity per glucose unit on chain length of oligosaccharides was examined. The values of binding constant and thermodynamic parameters, assuming the 1:1 complex for TNS-amylose (number-average degree of polymerization, DPN = 17), were determined by the fluorescence titration. The values of thermodynamic parameters for 1:1 complex formation of TNS-α- and β-cyclodextrins were also determined and compared with those of TNS-amylose (DPN = 17). The fluorescence intensity of TNS in the presence of amylose (DPN = 600) decreased by the action of glucoamylase and taka-amylase A. The fluorescence of TNS-amylose (DPN = 17) system increased with the increased ionic strength. In the presence of pullulan, TNS fluorescence was also enhanced and decreased by the action of pullulanase. Amylopectin enhanced TNS fluorescence rather more strongly than amylose (DPN = 17) at the same concentration. In the presence of dextran, the fluorescence of TNS was scarcely enhanced. The degree of fluorescence enhancement of TNS in the presence of α-glucans seems to reflect the structures of α-glucans in solution, since TNS fluorescence is enhanced in the hydrophobic environment or by the disturbance of free intramolecular rotation.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 53
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Water-soluble, random copolymers containing L-methionine and N5-(3-hydroxypropyl)-L-glutamine have been prepared, fractionated, and characterized. The thermally induced helix-coil transitions of these copolymers in water have been investigated, and it has been found that incorporation of L-methionine increases the helix content of the polymers at all temperatures in the range of 0-60°C. The Zimm-Bragg parameters σ and s for the helix-coil transition in poly(L-methionine) in water were deduced from an analysis of the melting curves of the copolymers using the methods described in earlier papers.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 54
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2491-2506 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Normal vibrational analysis was carried out for DNA molecules in both A and B conformations as well as for A-RNA. A simplified backbone model was examined and expanded to include the backbone phosphate-group and the ribose ring. We applied the new force-constant refinement procedure discussed in the preceeding paper [Van Zandt, L. L., Lu, K.-C. & Prohofsky, E. W. (1977) Biopolymers, 16, 2481-90] to fit some observed frequencies in the Raman spectra for all three nucleic acids with the same set of force constants. The results indicate that the observed frequency shift can be attributed to the conformational change solely. We ignored the second-order differences in force constants for the different geometries. The agreement between the observed and calculated frequencies derived from the final refined set of force constants is good and apparently justifies this assumption. Two modes previously assigned to the symmetric diester O-P-O stretch and the symmetric dioxy O‥P‥O stretch are actually fitted. They are mainly backbone phosphate-group modes. The refined ribose-ring force-constants were transferred to the calculation of the vibrational spectrum of tetrahydrofuran. The overall agreement is again good. We discuss these calculations and the resulting normal modes. We also discuss the application of the Green-function refinement scheme and several strategies adopted to bias the convergence of the procedure.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 55
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1971-1986 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A study of the conformational states of the dinucleotide coenzyme NAD+ has been made using semiempirical energy calculations. Taking low-energy mononucleotide structures as starting conformations, energy minimizations have been performed. The lowest energy states are stacked structures, with interactions between the adenine and nicotinamide rings. Some structures show stabilization gained from electrostatic attractions between the positively charged nicotinamide and negatively charged phosphate oxygens. These predictions correlate well with the available experimental data.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 56
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Water-soluble block copolymers of the type (A)m-(B)n-(A)p, where (A)m,p was either poly(D,L-lysine-α,β,β,γ,γ,δ,δ-d7) or poly(D,L-lysine) and (B)n was either poly(L-alanine) or poly(L-phenylalanine), were synthesized for conformational studies by proton magnetic resonance spectroscopy. Analytical determination of the amount of the initiator fragment (n-hexylamine) at the C-terminus of the copolymers was used to obtain the number-average degrees of polymerization, DPn, and thereby, together with the amino acid composition, to establish the covalent structures of the polymers. The values of DPn were found to be much lower than those deduced from sedimentation equilibrium or form viscosity measurements. These deviations, which also are thought to have arisen in similar studies reported in the literature, are attributable to intermolecular aggregation; the relation of such aggregation to covalent structure (and its effect on the polymerization reaction) is discussed in terms of the conditions and mechanism of synthesis of block copolymers of amino acids.
    Zusätzliches Material: 5 Tab.
    Materialart: Digitale Medien
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  • 57
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 58
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1879-1894 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Poly(Lys48, His52), a random copolypeptide of L-lysine (48%) and L-histidine (52%), was used as a model protein for investigating the effects of protonation on the imidazole group of histidines on protein binding to DNA. The complexes formed between poly(Lys48, His52) and DNA were examined using absorbance, circular dichroism (CD), and thermal denaturation. Although increasing pH reduces the charges on histidine side chains in the model protein, the protein still binds the DNA with approximately one positive charge per negative charge in protein-bound regions. Nevertheless, CD and melting properties of poly(Lys48, His52)-DNA complexes still depend upon the solution pH which determines the protonation state of imidazole group of histidine side chains. At pH 7.0, the complexes show two characteristic melting bands with a tm (46-51°C) for free base pairs and a t′m (94°C) for protein-bound base pairs. The t′m of the complexes is reduced to 90°C at pH 9.2, although at this pH there is still one lysine per phosphate in protein-bound regions. Presumably, the presence of deprotonated histidine residues destabilizes the native structure of protein-bound DNA. The binding of this model protein to DNA causes a red shift of the crossover point and both a red shift and a reduction of the positive CD band of DNA near 275 nm. This phenomenon is similar to that caused by polylysine binding. These effects, however, are greatly diminished when histidine side chains in the model protein are deprotonated. The structure of already formed poly(Lys48, His52)·DNA complexes can be perturbed by changing the solution pH. However, the results suggest a readjustment of the complex to accommodate charge interactions rather than a full dissociation of the complex followed by reassociation between the model protein and DNA.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1929-1943 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A theoretical analysis of the conformation of the octapeptide hormone Asn1, Val5 angiotensin II has been carried out by semiempirical potential energy calculations. A preliminary study of the Ala6-Pro-Ala molecule, which mimics the angiotensin backbone, provided us with likely backbone structures on which the effect of the full side chains of the hormone could be assessed. For angiotensin II, the calculations show that only a small number of folded, compact conformations have a high probability of existence. This is the consequence of favorable packing and of the presence of proline in position 7. These results are consistent with various experimental data, both structural and biological. This method is readily applicable to the study of analogs of the hormone or to other peptides of comparable size.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 60
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1993-2004 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The interaction between DNA and ionen polymers, -[N+(CH3)2(CH2)mN+(CH3)2(CH2)n]l-, with m-n of 3-3, 6-6, and 6-10 were examined in order to know how the binding behavior of cationic polymers with DNA depends on the charge density of polycation. The ionen polymer has no bulky side chain and the binding forces with DNA would be attributed mainly to electrostatic interaction. When 3-3 ionen polymers were added to DNA solution, precipitable complexes with the ratio of cationic residue to DNA phosphate (+/-) of 1/1 and the free DNA molecules were segregated, while 6-6 and 6-10 ionen polymers formed soluble complexes with DNA molecules up to (+/-) = 0.5. This suggests that 3-3 ionen polymers bind cooperatively with DNA while 6-6 and 6-10 ionen polymers bind noncooperatively. The cooperative binding of 3-3 ionen polymer and the noncooperative binding of 6-6 ionen polymer were also supported by the thermal melting and recooling profiles from the midpoint between first and second meltings. It was concluded that the charge density of DNA phosphate is a critical value determining whether the ionen polymers bind to DNA by a cooperative or by a noncooperative binding, since the distance between successive cationic charges of 3-3 ionen polymer is shorter than that between successive phosphate charges on DNA double helix and those of 6-6 and 6-10 ionen polymers are longer.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 61
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2091-2104 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Quasielastic light scattering is used to study the effect of ionic strength on the dynamic behaviour of DNA. In a first approach the spectrum of scattered light is analyzed in terms of a single relaxation process. The large difference between the observed behaviour and that expected according to a pure diffusional process reflects the contribution associated with internal modes, which increases with decreasing ionic strength. Such behaviour is better analyzed in terms of a double relaxation process by using two relaxation times, the reciprocals of which are equal to DK2 and DK2 + τi-1 (K), respectively, where τi (K) is an average value describing the set of modes observed at a given K value. Relative intensity and relaxation times, which are the more accurate parameters, were used to interpret the results. The observed increase of the relative contribution of internal modes with decreasing ionic strength is actually a relative decrease of the diffusional contribution induced by a corresponding increase of the radius of gyration RG. On the other hand, the reciprocal τi-1 (K) of the relaxation time is a linear function of K2 in the analyzed KRG range and is insensitive to ionic strength between 10-2M and 1M. These results, when discussed according to Rouse's model, lead to define for each value of τi-1 (K) a corresponding mean-squared equilibrium length 〈μi2〉 which is found to be a linear function of K-2.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 63
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2755-2771 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Derivatives and peptides of β-nitrobenzyl-L-aspartates were studied with high-field nmr. Differences were observed between the chemical shifts of protons located near the extremity of the principal chain as a function of the terminal group. These differences are explained by conformational calculations which exclude the existence of an hydrogen bond and demonstrate the influence of the aromatic ring position on the protons of the main chain. Both nmr experiments and conformational analysis indicate that conformations are nearly the same for ortho, meta, and para nitro substitution. These conclusions are in good agreement with Karplus relationship applied to the α and β protons.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 64
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 81-94 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Excess small angle X-ray scattering in solvents of differing electron density has been calculated from the crystal structures obtained for rubredoxin, trypsin inhibitor, myogen, ferricytochrome c2, ribonuclease S, lysozyme, nuclease, myoglobin, α-chymotrypsin, elastase, subtilisin, carboxypeptidase A, thermolysin, methemoglobin, deoxyhemoglobin, and a single polypeptide chain of M4 lactate dehydrogenase. The scattering curves for each protein can be reproduced by the sum of three curves, with the weighting of the three curves depending on the electron density of the solvent. The radius of gyration obtained from the small angle X-ray scattering by globular proteins in aqueous solution will usually exceed the values defined by the shape of the macromolecule. Deviations for certain of the proteins cited are calculated to be as large as 6%. These deviations arise from the tendency for the amino acid residues with low electron density to be situated closer to the center of the protein than the amino acid residues of high electron density. An upper limit of 19% is obtained for the discrepancy between the radius of gyration defined by the shape of a spherical globular protein of typical amino acid composition and the apparent radius of gyration measured for that protein in water by small angle X-ray scattering.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 157-185 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ability of the macrotetrolide nactins to complex selectivity with a wide variety of cations makes these ionophorous antibiotics important model systems for the study of biologic ionic transport. We report a Raman spectroscopic investigation of the Na+, K+, Rb+, Cs+, Tl+, NH4+, NH3OH+, C(NH2)3+, and Ba++ complexes of nonactin, monactin, and dinactin in 4:1 (v/v) CH3OH/CHCl3 and in the solid state. The nactins display characteristic spectral changes upon complexation, some of which are specific for a given cation. In the K+, Rb+, Cs+, NH3OH+, and C(NH2)3+ complexes, which are apparently isosteric, the ester carbonyl stretch frequency is found to be linearly proportional to the cation-carbonyl electrostatic interaction energy, as calculated from a simplified model. Deviations for the Na+, NH4+, Tl+, and Ba++ complexes are interpreted as arising from additional nonelectrostatic interactions. Additional information is obtained from other spectral regions and from measurements of depolarization ratios. Spectra of the nactin complexes differ from each other more in the solid state than in solution, reflecting the effects of crystalline contact forces.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 225-230 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 231-246 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The interaction of water with collagenous tissue was investigated using dynamic mechanical spectroscopy and cryogenic X-ray techniques. The loss spectrum was found to be very sensitive to water which is highly associated with the macromolecule. Two water-sensitive loss peaks were observed below 0°C: the β2 or “water dispersion” at 150°K and the β1 at 200°K which is attributed to motion of polar side chains. Changes in peak temperature and intensity were not continuous with water content, but exhibited regimes in behavior which were associated with two types of nonfreezable water, structural and bound water. In cryogenic X-ray experiments, specimens which contained some freezable water exhibited reflections identified with the cubic form of ice. These ice crystals underwent an irreversible transition to the more common hexagonal form when warmed above 200°K. On the basis of these experiments, a model for the hydration of native collagenous tissue was proposed.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
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  • 68
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 299-316 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Conformation behavior of polyethylenimine has been examined by studies of the fluorescence characteristics of derivatives of the polymer containing pyrenyl ligands. Excimer formation within the macromolecular matrix serves as a sensitive probe of group proximities. The experimental observations combined with nearest neighbor analyses lead to quantitative assessments of the extent of interaction between polymer side chains.
    Zusätzliches Material: 7 Ill.
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  • 69
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 387-401 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The chiroptical properties of S-proline conformational isomers are examined on a theoretical model in which electronic wave functions are obtained from semiempirical molecular orbital calculations. The CNDO/S molecular orbital model is used to perform SCF-MO calculations on ground state electronic structure and excited states are constructed in the virtual orbital-configuration interaction approximation. Electronic rotatory strengths and dipole strengths are calculated directly from the complete (but approximate) molecular electronic wave functions. Zwitterionic, cationic, and anionic S-proline structures are studied twotypes of conformational variables are represented in the calculations: (1) pyrrolidine ring conformation; and (2) rotation about the Cα-COO- bond. Rotatory strengths are found to be somewhat sensitive to rotational isomerism about the Cα-COO- bond, but are found to be rather insensitive to conformational changes within the pyrrolidine ring. The CD spectrum of zwitterionic S-proline down to ∼160 nm appears to be well accounted for by the theoretically calculated results if conformational preferences with respect to rotation about the Cα-COO- bond can be assumed to exist in solution media. Furthermore, spectra-structure correlations are offered for the anionic and cationic forms of S-proline in solution.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 70
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 415-426 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A series of stereoregular α-(1 → 6) linked glucomannans have been prepared by Lewis acid-catalyzed copolymerization of anhydro sugar derivatives followed by debenzylation. The products have been characterized for mole fraction of the individual monomer, and sequence lengths have been calculated from copolymerization data. The viscosity, specific rotation, and 13C nmr spectra have been correlated with the structure of the various copolymers.
    Zusätzliches Material: 3 Ill.
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  • 71
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
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  • 72
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 469-495 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper presents the results of a stereochemical analysis of local interactions in unfolded protein chains (sterical repulsions, hydrogen, and hydrophobic bonds, etc.) by means of space-filling modeles. On the basis of this analysis, an evaluation is made of thermodynamic parameters controlling the building-in of all the 20 natural amino acid residues in all the physically possible position of local secondary structures (α-helices, including α-helices with short fragments of helices 310 at the C-terminus; β-bends of different types, helices 310, and their combinations) as well as thermodynamic parameters of separate hydrogen bonds of polar side groups with the neighbor peptide groups (“local contacts”). The accuracy of the obtained results is discussed.
    Zusätzliches Material: 6 Ill.
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  • 73
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 545-549 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The translational diffusion coefficient of a pure sample of α-chymotrypsinogen A is measured by laser light scattering to give a value of D20,w0 = (8.40 ± 0.15) × 10-7 cm2/sec.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 74
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The exchange rate of the indole nitrogen proton with solvent water protons was measured as a function of pH and temperature for tryptophan, N-methyl tryptophan, glycyl tryptophan, tryptophanamide, tryptophylglycine, and tryptophylglycyl glycine. The nmr observation was by long-pulse Fourier transform methods, and kinetics were inferred from saturation recovery, H2O transfer of saturation, and linewidth. There are observable differences between the rates of these compounds, but all are describable within a factor of two by specific acid and base-catalyzed rates kH = 100 and kOH = 108 1/mol-sec at 27°C. It is concluded that this behaviour is representative of this proton on the indole side chain in a random-chain peptide exposed to water.
    Zusätzliches Material: 2 Ill.
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  • 75
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Stoichiometric mixtures of acridine orange with dermatan sulfate at total dye concentrations ≤ 1 × 10-5 M show fluorescence maxima at 540 nm and 660 nm on excitation at 436 nm. By means of membrane filtration, it is directly demonstrated that the species emitting at 540 nm is due only to unbound dye whereas the 660-nm emitting species is due to bound dye. It is, therefore, possible to differentiate unbound acridine orange from its dermatan sulfate complex solely by spectroscopic methods. Thermodynamic binding parameters can be calculated from rapid spectroscopic measurements without disturbing the system.
    Zusätzliches Material: 1 Ill.
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  • 76
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977) 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 731-747 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general kinetic analysis for unimolecular three-species models is presented. Criteria are established for each model in order to allow selection among alternative models on the basis of their amplitude behavior. These criteria are applied to the previously reported kinetic data for the folding transitions of lysozyme and cytochrome c in guanidine hydrochloride. The degree of success in applying these criteria is found to depend on the extent to which the apparent rate constants, λ1 and λ2, approach each other in certain conditions. Ikai and Tanford have presented a similar kinetic analysis, although these authors considered only the case where no intermediate kinetic species was populated initially. For one protein system, namely, ribonuclease A (RNase A), at least one stable intermediate exists after unfolding outside of the equilibrium transition zone. The criteria developed by Ikai and Tanford cannot be applied to RNase A kinetics and, therefore, a more general analysis is presented. Previously published studies of the reversible folding kinetics of lysozyme and cytochrome c are reexamined using the current amplitude analysis, and it is found that both of these folding transitions can be described by the three-species model, \documentclass{article}\pagestyle{empty}\begin{document}$$ U_{1} \rightleftharpoons U \rightleftharpoons N $$\end{document} used previously to describe the folding kinetics of RNase A (U1 and U2 are two forms of unfolded enzyme and N is the native species). These results suggest that this three-species model may provide a fairly general description of the reversible folding kinetics of small proteins. As an outgrowth of the current analysis, several suggestions for experimental design in studying protein folding will be presented and discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 78
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The copolymer which has both ligand sites (4-vinylpyridine) and redox sites (N-(p-vinylbenzyl)-3-carbamoyl-1,4-dihydropyridine) was synthesized by the dithionite reduction of the copoly(4-vinylpyridine-N-(p-vinylbenzyl)-3-carbamoylpyridinium chloride) and the reduction of a central ferric-iron of ferriprotoporphyrin IX by the above-described copolymer was studied spectrophotometrically in dimethyl sulfoxide. The rate of the reduction by the copolymer was much faster than by N-benzyl-3-carbamoyl-1,4-dihydropyridine. This acceleration by the copolymer could be explained by the intramolecular reduction of ferriprotoporphyrin IX which was coordinated by the pyridine residue of the copolymer.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 965-982 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We have investigated the B to A conformation change of DNA double helices by a new method “soft-mode analysis.” We find theoretically that a mode does soften when the vibration normal modes are perturbed by increasing the electrostatic interaction between the unbalanced charges on atoms in the double helix. The same mode also softens for enhanced van der Waals interactions. The mode softening indicates the onset of conformation change. The enhancing of the electrostatic and van der Waals interaction mimic the effect of decreasing the polar nature of the solvent or water of hydration associated with the B conformation DNA. We discuss qualitatively the concept of soft modes and their relation to conformation change as well as their applicability to macromolecules. We discuss previous work in which the normal vibrational modes have been calculated. We also discuss the displacement which comes from the soft mode and show that it correlates very well with that expected for the B to A conformation charge.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1015-1031 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An electron microscope study of collagen fibrils from fixed tail tendons of rats has revealed that from some time shortly after birth until maturity, the fibril diameters have a bimodal distribution. The “two” types of fibril are indistinguishable in both transverse and longitudinal section. Unfixed specimens of eight-week-old-tail tendon showed a similar bimodal distribution of diameters though the positions of the peak values compared to fixed specimens of an eight-week-old-tail tendon were shifted upwards by about 30%. It has also been shown quantitatively that the polar collagen fibrils are directed randomly “up” and “down” with respect to their neighbors. Whilst it has been suggested by others that anastomosis is a feature of collagen structure, the results presented here do not support this hypothesis. Fibrillar units ∼ 140 Å in diameter have been observed and the possibilities that these are elastic fibers or the breakdown products of collagen fibrils have been considered.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 81
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The addition of a lytic layer to a preformed linear sucrose gradient induces a temporary (up to half a day) initial gradient of considerable steepness which retards the sedimentation of large (〉T4) DNAs. Centrifugation at sufficiently slow angular velocities permits the temporary initial gradient to disappear and therefore the sedimentation distance increases, yielding a rotor speed dependent effect on sedimentation distance. Gradients which are free of this effect are described and shown to permit mouse leukemia cell DNA to sediment independently of rotor speed (5-30 krpm).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 82
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The thermally induced helix-coil transitions of three A-T DNAs, d(A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n, were studied. Experimental transition curves of the DNAs were analyzed using the loop entropy model of DNA melting. The calculation of the melting curve of d(A-A-T)n·d(A-T-T)n is presented using the integral equation formalism of Goel and Montroll. The aim of this work was to evaluate thermodynamic parameters which govern DNA stability and to test the theoretical model employed in the analysis. Our results show (1) an excellent over-all agreement between theory and experiment, (2) a loop entropy exponent k = 1.55 ± 0.05 provided the best fit to all the polymer transition curves, (3) the evaluated stacking free energies reflect the relative stability of the DNAs, and (4) the stacking energies of the ApA·TpT dimer evaluated from d(A)n·d(T)n and d(A-A-T)n·d(A-T-T)n differ. The last result is consistent with different conformations for the dimer in these two polymers.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 83
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Concentration and temperature dependences of the 1H nmr spectra of N-acetyl-L-proline N-methylamide were observed in various solvents [CCl4, CDCl3, (CD3)2CO, (CD3)2SO, H2O, and D2O]. The fraction of the cis isomer (with respect to the bond between the acetyl carbonyl carbon and prolyl nitrogen atoms) depends greatly on the solvent used; the fraction of the cis isomer is higher in polar solvents than in nonpolar solvents. It depends also on concentration and temperature in nonpolar solvents but not in polar solvents. In nonpolar solvents the trans isomer mostly exists in the γ-turn structure with an intramolecular hydrogen bond and the cis isomer tends to form molecular aggregates by intermolecular hydrogen bonds. In polar solvents both the cis and trans isomers exist in monomeric forms which interact with solvent molecules. The pH dependences of the N-methyl proton resonances indicate that the γ-turn structure of the trans isomer is present also in aqueous solution, though its population is difficult to determine. Apparent enthalpy and entropy changes for the conversion of the trans isomer to cis isomer are evaluated for various solvents. The results are discussed in terms of the intra- and intermolecular hydrogen bondings.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1357-1361 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 85
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1387-1395 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cyclo(D-Leu-L-Leu) and cyclo(L-Leu-L-Leu) were synthesized, and their carbon-13 nmr spectra at 65 MHz were examined in dimethylsulfoxide and trifluoroacetic acid solutions. The chemical shift data are consistent with a boat or “twisted” boat conformation of the diketopiperazine ring in both solvents. There was no indication of protonation of the cyclic dipeptides by trifluoroacetic acid. Attempts at polymerizing the cyclic dipeptides were unsuccessful.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1435-1448 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This paper presents new applications of the McMillan-Mayer solution theory to dispersions of highly charged colloidal cylinders in monovalent salt solutions. The thermodynamic solution properties are given in terms of the virial expansions relating to a Donnan membrane equilibrium. General expressions are derived for the second Donnan pressure virial coefficient B2 and for the first two salt distribution coefficients A1 and A2. The effect of electric interactions is represented as an increased effective diameter dB or dA of the colloidal cylinder. This yields the simple excluded volume expressions B2 = πdBL2/4 and A1 = πdA2L/4 for hard cylinders of length L and diameter dB and dA, respectively. The coefficient A2 is derived from the dependence of B2 on the salt concentration.Computations are made for double-stranded DNA in sodium chloride solutions with the DNA model developed in the preceding paper: a uniformly charged cylinder, with size and charge consistent with transport experiments, and surrounded by a Gouy double layer. In 1-0.005M sodium chloride solutions dB is found to vary from 29 Å to about 220 Å, and dA from 30 Å to about 170 Å, with little sensitivity to the uncertainties in the kinetic diameter d ≈ 24 Å and the experimental ζ potentials of DNA. Corresponding results predicted by the classical Donnan theory are 6-167 times too high for B2.Values of A2 are relatively small, in line with the expected rapid convergence of the virial expansion for the salt distribution. This is consistent with a phase transition from random to parallel orientation of the cylinders predicted first by Onsager for hard cylinders on the basis of B2, but not yet observed for DNA in simple salt solutions.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1505-1512 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The interaction of ox ligamentum nuchae elastin (native, purified, and soluble) with different solvents (water, ethylene glycol, methanol, and 2,2,2-trifluoroethanol) was investigated by means of differential scanning calorimetry. The unfreezable solvent content and the corresponding solvent to elastin residue molar ratio were determined from the melting endotherms of the freezable solvent present in these systems. The molar ratio obtained in the case of water and ethylene glycol agrees with hypothesis of a direct solvation of the main chain peptide group and is interpreted according to a model previously proposed for polyamides. Quite different molar ratios are obtained in the case of the two monofunctional solvents and no model can be proposed at present to explain their interaction with the protein.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 89
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis and characterization of water-soluble random copolymers containing L-asparagine with N5-(4-hydroxybutyl)-L-glutamine, and the thermally induced helix-coil transitions of these copolymers in water, are described. The incorporation of L-asparagine was found to decrease the helix content of the polymers in water at all temperatures. The Zimm-Bragg parameters σ and s for the helix-coil transition in poly(L-asparagine) in water were deduced from an analysis of the copolymer melting curves in the manner described in earlier papers. The computed values of s indicate that asparagine destabilizes helical sequences at all temperatures in the range 0-60°C.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 90
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1593-1607 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High-molecular-weight poly(0,0′-dicarbobenzoxy-L-β-3,4-dihydroxyphenyl-α-alanine) was prepared by the N-carboxyanhydride method. From the results obtained by a study of the optical rotation, nuclear magnetic resonance, and solution infrared absorption, the conformation of poly(0,0′-dicarbobenzoxy-L-β-3,4-dihydroxyphenyl-α-alanine) depended greatly on the solvent taking a right-handed helix with [θ]225 = -13,600 ∼ -18,900 in alkyl halides, a left-handed helix with [θ]228 = 22,100 ∼ 24,800 in cyclic ethers or trimethylphosphate, and a random coil structure in dichloroacetic acid, trifluoroacetic acid, or hexafluoroacetone sesquihydrate. The polypeptide underwent a right-handed helix-coil transition in chloroform/dichloroacetic acid (or trifluoroacetic acid) mixed solvents and a left-handed helix-coil transition in dioxane/dichloroacetic acid (or trifluoroacetic acid) mixed solvents. The results were compared with those of poly(0-carbobenzoxy-L-tyrosine).
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 91
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1677-1686 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Acetyl-(dehydro-Phe) and acetyl-bis(dehydro-Phe) groups have been attached to the ε-amino group of the lysine residues of the copolymer poly(Glu92Lys8) by reacting this last with acetyl-(dehydro-Phe)-azlactone and acetyl-bis(dehydro-Phe)-azlactone, respectively.In the latter case induced CD is observed between 250 and 330 nm, due to the relative dissymmetric disposition of the two dehydro-Phe groups under the chiral field of the polypeptide chain.pH dependence of the induced CD, observed for the copolymer and lacking in the lowmolecular-weight structural model, is related to the α-helical and random coiled conformation of the polypeptide chain.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2143-2165 
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A statistical theory of the linear dichroism of DNA-like chains is presented for two models which are discrete versions of the wormlike coil. In the final form the linear dichroism of the entire chain is related directly to the dichroic properties of a chain segment (base pair). Though the derivations are somewhat complicated, the result [Eq. (28)] is simple and the required statistical parameters can be easily calculated for either model from measured values of the persistence length. In fact, for molecules as stiff as double-stranded DNA, the results can be reduced with good accuracy to the form \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{\Delta \varepsilon (chain)}}{{\Delta \varepsilon (segment)}} = \frac{{P_{\infty} }}{l}\frac{r^{2}}{{\langle r^2 \rangle_0 }} $$\end{document} showing that the “optical persistence” given on the left is directly proportional to the structural persistence, P∞/l. As in previous theories the results are restricted to chains in their Gaussian limit.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 93
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A histidine-containing cyclic dipeptide, cyclo(D-Leu-L-His), was almost 20 times as efficient a catalyst as imidazole in the hydrolysis of p-nitrophenyl laurate. The effect of dioxane on the hydrolysis showed that hydrophobic interaction between the cyclic dipeptide and the ester is very important. This reaction obeyed the Michaelis-Menten kinetics, and the Michaelis constant Km was as low as 9.98 × 10-5M. Since the linear dipeptide having D-Leu-L-His sequence was nearly inactive in the hydrolysis, the functional groups of cyclo(D-Leu-L-His) in a specific arrangement held by the rigid backbone must have cooperated in the fast hydrolysis. Very weak catalysis by the diasteremeric cyclic dipeptide, cyclo(L-Leu-L-His), in the hydrolysis supported the above view.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 14-21 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 22-27 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977) 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. A4 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Chemie in unserer Zeit 11 (1977), S. 64-64 
    ISSN: 0009-2851
    Schlagwort(e): Chemistry ; Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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