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  • 1
    Electronic Resource
    Electronic Resource
    The cytoplasmic pH in photosynthesizing cells of the green alga Chlorella fusca, measured by P-31 NMR spectroscopy (1987)
    Springer
    Archives of microbiology 147 (1987), S. 25-29 
    Details
    ISSN: 1432-072X
    Keywords: Chlorella fusca ; Cyclic photophosphorylation ; Cytoplasmic pH ; Green algae ; P-31 NMR spectroscopy ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract P-31 NMR investigations were performed with the green alga Chlorella fusca under anaerobic conditions in the dark and in the light. In spectra of cells in the dark the signal of intracellular, nonvacuolar Pi indicates a pH in its chemical environment of 7.0–7.2. Upon illumination this signal looses intensity and shifts to lower field, corresponding to a pH of 7.7. Further downfield no other signal that could be attributed to a Pi-pool in more alkaline environment was detected. By the use of 2-deoxyglucose-6-phosphate as an indicator of cytoplasmic pH, this Pi-signal was assigned to the cytoplasm. The pH increase in the cytoplasm upon transfer of cells from the dark to the light is the same as that previously observed upon transfer of cells from anaerobic to aerobic conditions. In cells performing only cyclic photophosphorylation the cytoplasmic pH is lower than in photosynthesizing cells but still 0.2 pH units higher than in the cells in the dark. The reasons for the missing of a signal of stromal Pi and for the difference in cytoplasmic pH in photosynthesizing cells and those capable only of cyclic photophosphorylation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00492900
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  • 2
    Electronic Resource
    Electronic Resource
    P-31 in-vivo NMR investigation on the function of polyphosphates as phosphate-and energysource during the regreening of the green alga Chlorella fusca (1989)
    Springer
    Archives of microbiology 152 (1989), S. 167-171 
    Details
    ISSN: 1432-072X
    Keywords: Chlorella fusca ; Green alga ; Nitrogen starvation ; Polyphosphates ; P-31 in-vivo NMR spectroscopy ; Regreening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The green alga Chlorella fusca accumulates polyphosphates under conditions of nitrogen starvation while deassembling the photosynthetic apparatus. The polyphosphate content of cells regreening after resupply with nitrate under different culture conditions was investigated by P-31 in-vivo NMR spectroscopy. Neither phosphate deficiency nor anaerobiosis during the first hours of regreening inhibited the recovery of the cells. Polyphosphates were degraded during regeening. Differences in the amount of polyphosphates of phosphate supplied and deficient cells occurred only after more then 8 h. After 16 h phosphate deficient cells had still 75% of the polyphosphate content of phosphate suppled cells. In cells kept under anaerobic conditions polyphosphate degradation was much higher than in oxygen supplied cells. After 8 h they contained less than 50% of the polyphosphate content of oxygen supplied cells. These data suggest that polyphosphates serve as obligatory phosphate source during regreening and may be used as an energy source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00456096
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Distribution of polyphosphates in cell-compartments of Chlorella fusca as measured by 31P-NMR-spectroscopy (1986)
    Springer
    Archives of microbiology 144 (1986), S. 48-54 
    Details
    ISSN: 1432-072X
    Keywords: Chlorella fusca ; Green alga ; 31P-NMR-spectroscopy ; Polyphosphates ; Cellular localization ; Metal-ion complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In suspensions of the green alga Chlorella fusca the influence of high pH and high ethylene-diamine-tetraacetic acid concentrations in the external medium, of French-press and perchloric acid extraction of the cells and of alkalization of the intracellular pH on the polyphosphate signal in 31P-nuclear magnetic resonance (31P NMR) spectra was investigated. The results show that part of the polyphosphates of asynchronous Chlorella cells are located outside the cytoplasmic membrane and complexed with divalent metal-ions. These polyphosphates are tightly bound to the cell wall and/or the cytoplasmic membrane and are not susceptible to hydrolyzation by strong acid at room temperature, in contrast to the intracytoplasmic polyphosphates. Upon alkalization of the internal pH of Chlorella cells, polyphosphates, previously not visible in the spectra become detectable by 31P-NMR-spectroscopy. 31P-NMR spectroscopic monitoring of polyphosphates during gradual alkalization of the extra-and intracellular space is proposed as a quick method for the estimation of the cellular polyphosphate content and distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454955
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  • 4
    Electronic Resource
    Electronic Resource
    N-15 in vivo NMR spectroscopic investigation of nitrogen deprived cell suspensions of the green alga Chlorella fusca (1989)
    Springer
    Archives of microbiology 151 (1989), S. 434-438 
    Details
    ISSN: 1432-072X
    Keywords: Amino acid metabolism ; Chlorella fusca ; Green alga ; N-15 in vivo NMR spectroscopy ; Nitrogen deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The possibility to apply N-15 in vivo NMR spectroscopy to study algal N-metabolism has been investigated. N-15 labelled cells of the green alga Chlorella fusca, subjected to nitrogen starvation and N-14 labelled cells supplied with K15NO3 after prolonged nitrogen starvation were monitored by N-15 in vivo NMR spectroscopy at different times after the change in their nitrogen supply. During 20–40 min, necessary for the acquisition of 1 spectrum, the cells were under dark anaerobic conditions, but the relative amounts of the metabolites detected did not change. Signals from 2 acid amides, from the side chain nitrogens of arginine and lysine, from prolin as well as 4 signals from α amino groups of amino acids were detected. Besides two signals not yet reported in the literature were found. They may be due to amino compounds, but not to amino acids. The amount of free amino acids in the cells increases not only upon resupply of nitrogen starved cells with nitrate but also during the first hours after nitrate depletion. The spectra obtained from N-15 labelled autospores show that N-15 in vivo NMR spectroscopy can be applied to the investigation of N metabolism of the cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00416603
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  • 5
    Electronic Resource
    Electronic Resource
    Validation and error analysis of a strata modelling technique (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 305-321 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; finite difference analysis ; error analysis ; strata control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary Sources of error are investigated for a two-dimensional finite difference computer program designed to model strata deformation. The program calculates the displacements of a mesh of ‘mass points’, by the iterative solution of equations of equilibrium for the stresses acting on each mass point. The effect of errors on both displacement estimates and stress estimates is considered. Round-off errors are discussed analytically, while the effect of choosing too coarse a mesh density is demonstrated by comparison of two runs of the program with identical material properties, but different mesh densities. The influence of boundary conditions and the result of incomplete relaxation of the finite difference equations is estimated by comparison with Kirsch's analytical solution for a thin plate of finite width with a circular hole under unidimensional load. As a result of the analysis, estimators for stresses and displacements are derived, which make allowance for some of the sources of error; suitable boundary conditions for first and subsequent runs of the program are proposed; and a convergence criterion for the iterative process is suggested. These results are then applied to simulations of mining situations, together with various refinements of the basic model, such as separation and ‘slip’ between adjacent strata, and an allowance for failure of material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00881119
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  • 6
    Electronic Resource
    Electronic Resource
    Stochastic methods for the prediction of strata behaviour (1984)
    Springer
    Geotechnical and geological engineering 2 (1984), S. 291-304 
    Details
    ISSN: 1573-1529
    Keywords: Coal mining ; strata control ; finite difference analysis ; stochastic methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary A two-dimensional finite difference computer program, with the facility to represent stratified material by means of a mesh of ‘mass points’ with different material properties in each square of the mesh, is adapted to run on a mesh whose material properties are selected stochastically from a specified distribution. The program uses an iterative method to solve the equations of equilibrium, giving estimates of displacements and stresses. Lattices of normally distributed (zero mean, unit variance) random values are produced: lattices of statistically independent values and lattices whose values are spatially correlated, to give the effect of gradual variations resulting in regions of positive values and regions of negative values. These lattices are used to generate the material properties: Young's modulus, Poisson's ratio and density. Each property has a specified mean and standard deviation for each material in the model, and the precise values for each mass point are calculated from the relevant lattices. A simple model with a square opening is used to investigate the effect of this stochastic generation of material properties, by comparison of stresses and displacements near the opening for runs of the program with (1) deterministic and (2) stochastic properties. Similar lattices of random values are used to introduce a stochastic element in the criterion for failure of materials. This is applied to a more realistic simulation of a mining situation, where Mohr's Criterion is used, with a stochastic component, to determine whether failure has occurred at each point of the mesh.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00881118
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