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  • Chemistry  (9)
  • Oscillatoria limnetica  (4)
  • lake restoration  (2)
  • 1990-1994  (13)
Publikationsart
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Verlag/Herausgeber
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Progress in the research of artemisinin-related antimalarials: An update (1994)
    Springer
    Pharmacy world & science 16 (1994), S. 169-180 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01872865
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  • 2
    Digitale Medien
    Digitale Medien
    Interspecific variation in pigmentation: implications for production estimates for shallow eutrophic lakes using an incubator (1992)
    Springer
    Hydrobiologia 238 (1992), S. 197-202 
    Details
    ISSN: 1573-5117
    Schlagwort(e): primary production ; spectral light distribution ; incubator ; laboratory scale enclosure ; Oscillatoria limnetica ; Prochlorothrix hollandica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In shallow, eutrophic Lake Loosdrecht, light attenuation and spectral changes with depth are pronounced due to high concentration of algae and tripton. Calculations of integrated daily primary production have been based on the photosynthesis-irradiance relationship (P/E-curve) obtained with the incubator technique. The suitability of this technique for estimating primary production in such a turbid lake was investigated by comparing P/E-curves for two differently pigmented algae, Oscillatoria limnetica and Prochlorothrix hollandica, in two laboratory systems differing in light regime. System (1) consisted of an incubator filled with tapwater, and system (2) was an algal culture in a laboratory scale enclosure (LSE). For O. limnetica the P/E-curves were identical. The P/E-curves for P. hollandica diverged considerably: the photosynthetic efficiency in the LSE (0.19 mg O2 (mg Chl)−1 h−1 (W m−2)−1 was about half of that obtained in the incubator (0.35 mg O2 (mg Chl)−1 h−1 (W m−2)−1. These results were explained by the interspecific variation in pigmentation. The photosynthetic efficiency of P. hollandica changed due to the dependence on the chlorophyll specific absorption for the whole photosynthetic waveband on the spectral light distribution, which for O. limnetica was approximately the same in the two light regimes. Column-integrated primary production computed with the photosynthetic characteristics of P. hollandica obtained in LSE, was 10–30% lower than the production based on incubator data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048789
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  • 3
    Digitale Medien
    Digitale Medien
    Coupling of phytoplankton and detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 51-59 
    Details
    ISSN: 1573-5117
    Schlagwort(e): phytoplankton ; Oscillatoria limnetica ; Prochlorothrix hollandica ; detritus ; shallow lakes ; lake restoration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake's trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00016095
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  • 4
    Digitale Medien
    Digitale Medien
    Dynamics of phytoplankton detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 61-67 
    Details
    ISSN: 1573-5117
    Schlagwort(e): phytoplankton ; epipelon ; Oscillatoria limnetica ; detritus ; shallow lakes ; lake restoration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A study was made of the mortality and aerobic decomposition of light- and phosphorus-limited cultures of Oscillatoria limnetica, a dominant phytoplankton species in shallow, eutrophic Lake Loosdrecht (The Netherlands). When placed in the dark at 20 °C, most cells died and lysed within twelve days. The labile organic matter was completely decomposed within three weeks. Absorbance spectra indicated that blue green algae may contributed significantly to the refractory dissolved substances in the lake. Refractory particulate matter constituted from 7 to 24% of the biomass of O. limnetica, depending on the growth rate before incubation in the dark. The decomposition rate of this fraction was 0.005 d−1. On a basis of a steady-state model of the dynamics of phytoplankton detritus, the areal organic dry weight concentration of the detritus in the lake is ca. 60 g m−2. This means the quantities of detritus in the seston and epipelon are about equal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00016096
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  • 5
    Digitale Medien
    Digitale Medien
    The ‘true’ growth efficiency of phytoplankton as influenced by light attenuation and insolation: implications of the photosynthesis-irradiance relationship (1992)
    Springer
    Hydrobiologia 238 (1992), S. 169-176 
    Details
    ISSN: 1573-5117
    Schlagwort(e): growth efficiency ; areal quantum efficiency ; light attenuation ; Oscillatoria limnetica ; shallow lakes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The ‘true’ growth efficiency (c) relates the light energy absorbed by phytoplankton to the production of biomass corrected for constant energy requirement of maintenance. Continuous culture studies have shown that, at constant incident irradiance, the value of c for both prokaryotic and eukaryotic species is constant. Culture data for the relevant conditions of incident light may be used for directly estimating the growth rate from daily insolation of optically deep, fully mixed lakes, when the light absorption by the phytoplankton can be established. In order to examine the influence of vertical light attenuation and daily insolation on c, computations were made on a basis of a photosynthesis-irradiance curve of light-limited Oscillatoria limnetica. For steady state growth, the ‘true’ growth efficiency is linearly related to the areal quantum efficiency of photosynthesis (ϕ a ). The computations showed that ϕ a remains constant at fluctuating vertical light attenuation, no matter whether the concentration of tripton or phytoplankton changes. The effect of insolation is great: ϕ a is 0.108 mol O2/E at very low light, but only 0.014 mol O2/E at 400 W m−2 subsurface downward irradiance. The results imply that a c-value obtained from cultures for summer averaged insolation must be corrected: between cloudy and clear days the value may vary by a factor of 2. The ‘true’ growth efficiency for cultures will decrease by about 10% when the same daily irradiation is dosed sinusoidally instead of constantly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048785
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360330802
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): molecular dynamics ; docking ; computer simulation ; substrate docking ; immunoglobulin ; rational drug design ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340190303
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  • 8
    Digitale Medien
    Digitale Medien
    Essential dynamics of proteins (1993)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 17 (1993), S. 412-425 
    Details
    ISSN: 0887-3585
    Schlagwort(e): normal modes ; constraint dynamics ; molecular dynamics ; lysozyme ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340170408
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  • 9
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): protein force field ; protein crystal ; protein hydration ; Ca2+ binding site ; molecular dynamics ; subtilisin ; computer simulation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: 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.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340140406
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  • 10
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: 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.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690370204
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