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  • Chemistry  (16)
  • 1990-1994  (9)
  • 1980-1984  (7)
  • 1965-1969
  • 1920-1924
  • 1
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1159-1166 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A molecular dynamics (MD) simulation was performed on the α-helix H8-HC5, the C-terminal part of myoglobin (residue 132-153), under periodic boundary conditions in two different solutions, water and water with 30% (v/v) 2,2,2-trifluoroethanol (TFE), at 300 K to investigate the stability of the helix. In both simulations, the initial configuration was a canonical right-handed α-helix. In the course of the MD trajectory in water (200 ps), the helix clearly destabilized and began to unfold after 100 ps. In the TFE solution, two stable parts of helical regions were observed after 70 ps of a 200-ps MD simulation, supporting the notion that TFE acts as a structure-forming solvent. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 2422-2430 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The water relaxation rates of several flavoproteins in the semiquinone state have been investigated by the spin echo technique. The results indicate a rather unspecific interaction between water and the protein-bound flavosemiquinones. An average interaction distance of 0.3-0.5 nm has been estimated. From the temperature dependence of the rate constants the free energy of activation for proton exchange is calculated to be about 17 kJ/mol. The rate of proton exchange is around 1011 s-1 for the flavosemiquinones investigated are accessible to water regardless of their ionic state.The large difference in relaxation rates of water protons between D- and L- amino-acid oxidases is noticeable. Oxynitrilase exhibits the highest whereas Azotobacter vinelandii flavodoxin shows the lowest water relaxation rate of the flavoproteins studied. The results are discussed in relation to the visible-light absorption properties of the flavoproteins.
    Additional Material: 1 Ill.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of the antimalarials dihydroqinghaosu (2), artemether (3), and artesunic acid (7a) derived from qinghaosu were elaborated by 1H-NMR spectroscopy, and supported with X-ray data obtained for 2 and 3. Several new derivatives, useful for the chemical characterization of dihydroqinghaosu (2) and artesunic acid (7a), were prepared.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 174-182 
    ISSN: 0887-3585
    Keywords: molecular dynamics ; docking ; computer simulation ; substrate docking ; immunoglobulin ; rational drug design ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple method is described to perform docking of subtrates to proteins or probes to receptor molecules by a modification of molecular dynamics simulations. The method consists of a separation of the center-of-mass motion of the substrate from its internal and rotational motions, and a separate coupling to different thermal baths for both types of motion of the substrate and for the motion of the receptor. Thus the temperatures and the time constants of coupling to the baths can be arbitrarily varied for these three types of motion, allowing either a frozen or a flexible receptor and allowing control of search rate without disturbance of internal structure. In addition, an extra repulsive term between substrate and protein was applied to smooth the interaction. The method was applied to a model substrate docking onto a model surface, and to the docking of phosphocholine onto immunoglobulin McPC603, in both cases with a frozen receptor. Using transrational temperatures of the substrate in the range of 1300-1700 K and room temperature for the internal degrees of freedom of the substrate, an efficient nontrapping exploratory search (“helicopter view”) is obtained, which visits the correct binding sites. Low energy conformations can then be further investigated by separate search or by dynamic simulated annealing. In both cases the correct minima were identified. The possibility to work with flexible receptors is discussed. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 17 (1993), S. 412-425 
    ISSN: 0887-3585
    Keywords: normal modes ; constraint dynamics ; molecular dynamics ; lysozyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Analysis of extended molecular dynamics (MD) simulations of lysozyme in vacuo and in aqueous solution reveals that it is possible to separate the configurational space into two subspaces: (1) an “essential” subspace containing only a few degrees of freedom in which anharmonic motion occurs that comprises most of the positional fluctuations; and (2) the remaining space in which the motion has a narrow Gaussian distribution and which can be considered as “physically constrained.” If overall translation and rotation are eliminated, the two spaces can be constructed by a simple linear transformation in Cartesian coordinate space, which remains valid over several hundred picoseconds. The transformation follows from the covariance matrix of the positional deviations. The essential degrees of freedom seem to describe motions which are relevant for the function of the protein, while the physically constrained subspace merely describes irrelevant local fluctuations. The near-constraint behavior of the latter subspace allows the separation of equations of motion and promises the possibility of investigating independently the essential space and performing dynamic simulations only in this reduced space. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 451-464 
    ISSN: 0887-3585
    Keywords: protein force field ; protein crystal ; protein hydration ; Ca2+ binding site ; molecular dynamics ; subtilisin ; computer simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In this paper we present a molecular dynamics (MD) simulation of subtilisin BPN′ in a crystalline environment containing four protein molecules and solvent. Con-formational and dynamic properties of the molecules are compared with each other and with respect to the X-ray structure to test the validity of the force field. The agreement between simulated and experimental structure using the GROMOS force field is better than that obtained in the literature using other force fields for protein crystals. The overall shape of the molecule is well preserved, as is the conformation of α-helices and β-strands. Structural differences are mainly found in loop regions. Solvent networks found in the X-ray structure were reproduced by the simulation, which was unbiased with respect to the crystalline hydration structure. These networks seem to play an important role in the stability of the protein; evidence of this is found in the structure of the active site. The weak ion binding site in the X-ray structure of subtilisin BPN′ is occupied by a monovalent ion. When a calcium ion is placed in the initial structure, three peptide ligands are replaced by 5 water ligands, whereas a potassium ion retains (in part) its original ligands. Existing force fields yield a reliable method to probe local structure and short-time dynamics of proteins, providing an accuracy of about 0.1 nm. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 182-192 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental measurements of the crystal-size distribution (CSD) clearly indicate a pronounced difference in the dynamic behavior of a 20- and 970-L continuous crystallizer that produces ammonium sulfate. The difference in their circulation time offers a probable explanation for this phenomenon. It causes different supersaturation profiles in the two crystallizers, which leads to internal fines dissolution in the large crystallizer. This contributes to the observed oscillations in the 970-L crystallizer as opposed to the first-order responses in the 20-L crystallizer. To numerically study the effect of the supersaturation profile a dynamic model, from which the MSMPR (mixed suspension mixed product removal) assumption is omitted, is developed. Calculated supersaturation profiles differ considerably for the 20-L, the 970-L and an imaginary 50,000-L continuous evaporative crystallizer. Coincident with changes in the supersaturation profiles, the numerical solution of the model indicates the tendency of large crystallizers to oscillate and supports this suggested explanation.
    Additional Material: 14 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1513-1518 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple point-charge potential, developed earlier for the calculation of intermolecular forces in molecular-dynamics simulations of liquid water, has been extended to include interactions between water molecules and polar groups of proteins. A complete potential for use in the simulation of protein dynamics in water is reported.
    Additional Material: 4 Tab.
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  • 10
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular proximity of cis/trans mixtures of 2,5-dimethoxy-1,4-bis[2-(3,4,5-trimethoxyphenyl)vinyl]benzene (MPV, 1) and polystyrene (PS) in mixtures of different MPV/PS weight ratios up to 60/40 is shown by 1H combined rotation and multiple pulse spectroscopy (CRAMPS) using 2D exchange experiments. The MPV/PS mixtures up to a weight ratio 60/40 are homogeneous, whereas the mixture with a weight ratio MPV/PS = 80/20 is heterogeneous. The comparison of the cross polarization/magic angle spinning (CP/MAS) 13C NMR spectra of pure MPV and of MPV mixed with PS shows significant linebroadening in case of intimate mixing, while the heterogeneous mixture shows some extra finestructure. The miscibility results were confirmed by proton spin-locking relaxation time measurements (T1ρH) on the mixtures. On intimate mixing, T1ρH is averaged out and varies linearly as a function of the composition of the mixture. CRAMPS-spectra and T1ρH measurements show that iodine-doped MPV/PS mixtures (weight ratios 40/60 and 60/40) are heterogeneous. Furthermore, doping causes a slight proton chemical shift change and reduces the T1ρH-values of those oligomer-polymer systems.
    Additional Material: 3 Ill.
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