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  • 1
    Electronic Resource
    Electronic Resource
    Progress in the research of artemisinin-related antimalarials: An update (1994)
    Springer
    Pharmacy world & science 16 (1994), S. 169-180 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01872865
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the stability of a 22-residue α-helix in water and 30% trifluoroethanol (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1159-1166 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330802
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the docking of substrates to proteins (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 19 (1994), S. 174-182 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340190303
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  • 4
    Electronic Resource
    Electronic Resource
    Essential dynamics of proteins (1993)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 17 (1993), S. 412-425 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340170408
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  • 5
    Electronic Resource
    Electronic Resource
    MD simulation of subtilisin BPN′ in a crystal environment (1992)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 451-464 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340140406
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of scale of operation on CSD dynamics in evaporative crystallizers (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 182-192 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690370204
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  • 7
    Electronic Resource
    Electronic Resource
    Miscibility of an oligo(p-phenylenevinylene) with polystyrene studied by solid-state nuclear magnetic resonance (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 2469-2476 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950715
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  • 8
    Electronic Resource
    Electronic Resource
    Moleküldynamik-Computersimulationen; Methodik, Anwendungen und Perspektiven in der Chemie (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 102 (1990), S. 1020-1055 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Während der letzten Jahrzehnte ist es möglich geworden, die Dynamik molekularer Systeme mit dem Computer zu simulieren. Bei Moleküldynamik(MD)-Simulationen löst man Newtons Bewegungsgleichungen für ein molekulares System, wobei die Trajektorien aller im System vorhandenen Atome erhalten werden. Aus diesen atomaren Trajektorien kann eine Vielzahl von Eigenschaften berechnet werden. Computersimulationen molekularer Systeme haben das Ziel, makroskopisches Verhalten aus mikroskopischen Wechselwirkungen zu errechnen. Die wesentlichen Beiträge, die eine mikroskopische Betrachtungsweise liefern kann, sind 1) das Verständnis, 2) die Interpretation experimenteller Ergebnisse, 3) halbquantitative Abschätzungen experimenteller Resultate und 4) die Fähigkeit, experimentelle Daten in Bereiche zu interpolieren oder zu extrapolieren, die im Labor nur schwer zugänglich sind. Eines der beiden grundlegenden Probleme auf dem Gebiet der Modellierung und Simulation molekularer Systeme besteht darin, den riesigen Konfigurationsraum, der von allen möglichen Molekülkonformationen aufgespannt wird, auf effiziente Weise nach jenen Bereichen global niedriger (freier) Enthalpie zu durchsuchen, die von einem molekularen System im thermischen Gleichgewieht besetzt sind. Das andere Grundproblem ist die Ableitung einer hinreichend exakten Energiefunktion oder eines Kraftfelds für Wechselwirkungen im zu untersuchenden molekularen System. Die Kunst der Computersimulation besteht auch darin, die unvermeidbaren Annahmen, Näherungen und Vereinfachungen für das molekulare Modell und den Rechenvorgang so zu treffen, daß ihre jeweiligen Beiträge zur Gesamtungenauigkeit von ähnlicher Größe sind, ohne dabei die interessierende Systemeigenschaft signifikant zu beeinflussen. Die Methodik und einige praktische Anwendungen der Computersimulation auf dem Gebiet der (Bio)chemie sind der Gegenstand dieser Übersicht.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19901020907
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  • 9
    Electronic Resource
    Electronic Resource
    Computer Simulation of Molecular Dynamics: Methodology, Applications, and Perspectives in Chemistry (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 29 (1990), S. 992-1023 
    Details
    ISSN: 0570-0833
    Keywords: Molecular dynamics ; Computer chemistry ; Force field calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During recent decades it has become feasible to simulate the dynamics of molecular systems on a computer. The method of molecular dynamics (MD) solves Newton's equations of motion for a molecular system, which results in trajectories for all atoms in the system. From these atomic trajectories a variety of properties can be calculated. The aim of computer simulations of molecular systems is to compute macroscopic behavior from microscopic interactions. The main contributions a microscopic consideration can offer are (1) the understanding and (2) interpretation of experimental results, (3) semiquantitative estimates of experimental results, and (4) the capability to interpolate or extrapolate experimental data into regions that are only difficultly accessible in the laboratory. One of the two basic problems in the field of molecular modeling and simulation is how to efficiently search the vast configuration space which is spanned by all possible molecular conformations for the global low (free) energy regions which will be populated by a molecular system in thermal equilibrium. The other basic problem is the derivation of a sufficiently accurate interaction energy function or force field for the molecular system of interest. An important part of the art of computer simulation is to choose the unavoidable assumptions, approximations and simplifications of the molecular model and computational procedure such that their contributions to the overall inaccuracy are of comparable size, without affecting significantly the property of interest. Methodology and some practical applications of computer simulation in the field of (bio)chemistry will be reviewed.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199009921
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