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  • 1990-1994  (1)
  • 1985-1989  (1)
  • 1960-1964
  • Aggregation  (1)
  • Nicotiana  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Changes in the density of microtubular networks in mesophyll cells and mesophyll derived protoplasts of Nicotiana and Triticum during leaf development (1993)
    Springer
    Planta 190 (1993), S. 10-16 
    Details
    ISSN: 1432-2048
    Keywords: Leaf development ; Mesophyll (cells, protoplasts) ; Microtubule (patterns, density) ; Nicotiana ; Tissue culture (in vitro competence) ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the density of microtubular mesh-works were analysed in mesophyll cells and mesophyll derived protoplasts of Nicotiana tabacum L. and Triticum aestivum L. during leaf development. The main purpose of this study was to test whether the low density, if not lack, of microtubular networks recently described in protoplasts that had been isolated from fully differentiated mesophyll cells happened during protoplast isolation or whether the loss of microtubules actually occurred during differentiation of the leaf tissue. Immunofluorescence microscopy showed that the density of the microtubular cytoskeleton in the leaf tissue decreased steadily after cessation of cell growth in both species. Nevertheless, in Triticum microtubule disappearance was swifter and occurred along a gradient from the base to tip of the leaf, a phenomenon reflecting the differences in the ontogeny between the dicotyledonous Nicotiana and the mono-cotyledonous Triticum leaves. Protein extraction from leaf tissues and Western blot analysis indicated that in both species the disappearance of microtubules was the result of a degradation of tubulin and not only due to a depolymerisation into tubulin subunits. When the cell walls were removed from live cells and the protoplasts released, the original patterns of the microtubules became obscured and, particularly in differentiated cells, the integrity and density of the microtubule strands deteriorated. The potential application of the density of the microtubular cytoskeleton as a marker in studies on differentiation and dedifferentiation in mesophyll cells and protoplasts is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195669
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular shape and dipole moment of alamethicin-like synthetic peptides (1985)
    Springer
    European biophysics journal 12 (1985), S. 67-73 
    Details
    ISSN: 1432-1017
    Keywords: Aggregation ; dielectric dispersion ; dipole moment ; molecular shape ; pore former
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The peptides Boc-(l-Ala-Aib-l-Ala-Aib-l-Ala)n-OMe, with n=2 (P10) and n=4 (P20), have been synthesized as purely hydrophobic models of the antibiotic alamethicin, which is known to be a voltage-dependent pore former in membranes and is apparently α-helical in lipophilic media. These peptides were investigated in 1-octanol, a solvent which resembles the membrane environment. From dielectric dispersion studies quantitative information on the molecular shape and dipole moments could be derived. Further independent data concerning conformation and extent of aggregation of the peptides were obtained by circular dichroism and ultracentrifuge measurements. The results suggest that the peptides assume the form of elongated particles having a significant amount of ordered secondary structure and carrying a dipole parallel to the long axis. Apparently the monomeric peptide molecules undergo, to some extent, a head-to-tail aggregation which is slightly enhanced at lower temperatures. Based on the high-frequency parts of the dielectric dispersion curves the lengths, diameters, and dipole moments of the monomer particles have been determined as 22.5 Å, 10 Å, 36 D (P10) and 28.5 Å, 12 Å, 64 D (P20).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00260429
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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