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  • 1
    Electronic Resource
    Electronic Resource
    Root elongation in saline solution related to calcium binding to root cell plasma membranes (1997)
    Springer
    Plant and soil 191 (1997), S. 67-76 
    Details
    ISSN: 1573-5036
    Keywords: calcium ; plasma membrane ; root elongation ; salinity ; sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To gain a better understanding of the relations between root elongation and the amount of Ca2+ bound to the plasma membrane (PM), melon plants were grown in aerated solutions containing different concentrations of CaCl2 with various concentrations of NaCl or mannitol. With increasing external concentrations of NaCl or mannitol, root elongation was suppressed. Addition of CaCl2 to the external medium alleviated the inhibition of root elongation by high concentrations of Na+, but not of mannitol. Root elongation in media containing high concentrations of NaCl was correlated with the computed amount of Ca2+ bound to the PM. A model describing relative root elongation (RRL) under salt stress was developed. This model takes into account the osmotic potential in the growing solution (based on the mannitol experiments) and the computed amount of Ca2+ bound to the PM. Calcium binding was calculated by applying a Gouy-Chapman-Stern sorption model using the same parameters deduced from studies on PM vesicles. This model combines electrostatic theory with competitive binding at the PM surface. The model for RRL allowed the computation of a critical value for the fraction of negative sites binding Ca2+ on the PM needed for nearly optimal (95%) root elongation. Any decrease below this critical value decreased the RRL. Root elongation of Honey Dew (salt-resistant cv.) was greater than that of Eshkolit Ha'Amaqim (salt-sensitive cv.) under NaCl stress. Nearly optimal root growth for Honey Dew and Eshkolit Ha'Amaqim occurred when 40% and 51% of total membrane charged sites were bound by Ca2+, respectively. The effect of osmotic potential on the suppression of root elongation was the same for the two cultivars. To our knowledge, this report provides the first fully quantitative estimates of PM-bound Ca2+ relative to salt toxicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004241506347
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  • 2
    Electronic Resource
    Electronic Resource
    Membrane destabilization induced by the human immunodeficiency virus type-1 fusion peptide (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 365-369 
    Details
    ISSN: 1573-3904
    Keywords: Conformational switching ; Membrane fusion ; Peptide conformation ; Peptide-lipid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The human immunodeficiency virus type-1 (HIV-1) fusionpeptide, corresponding to a sequence of 23 amino acidresidues at the N-terminus of the spike transmembranesubunit gp41, has the capacity to destabilizenegatively charged and neutral large unilamellarvesicles, representing, respectively, the acidic andthe neutral fraction of the plasma membrane lipids ofviral target cells. As revealed by infraredspectroscopy, the peptide associated with the vesiclesmay exist in different conformations. In negativelycharged membranes the structure is mainly anα-helix, while in Ca2+-neutralizednegatively charged membranes the conformation switchesto a predominantly extended conformation. In membranescomposed of zwitterionic phospholipids andcholesterol, the peptide also adopts a predominantextended structure. The α-helical structurepermeabilizes negatively charged vesicles but does notinduce membrane fusion. The peptide in β-typeconformation, on the other hand, permeabilizes neutralmembranes and triggers fusion. As seen by31P NMR, the latter structure also exhibits thecapacity to alter the lamellar organization of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008869409753
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  • 3
    Electronic Resource
    Electronic Resource
    Membrane destabilization induced by the human immunodeficiency virus type-1 fusion peptide (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 365-369 
    Details
    ISSN: 1573-3904
    Keywords: Conformational switching ; Membrane fusion ; Peptide conformation ; Peptide-lipid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The human immunodeficiency virus type-1 (HIV-1) fusion peptide, corresponding to a sequence of 23 amino acid residues at the N-terminus of the spike transmembrane subunit gp41, has the capacity to destabilize negatively charged and neutral large unilamellar vesicles, representing, respectively, the acidic and the neutral fraction of the plasma membrane lipids of viral target cells. As revealed by infrared spectroscopy, the peptide associated with the vesicles may exist in different conformations. In negatively charged membranes the structure is mainly an α-helix, while in Ca2+-neutralized negatively charged membranes the conformation switches to a predominantly extended conformation. In membranes composed of zwitterionic phospholipids and cholesterol, the peptide also adopts a predominant extended structure. The α-helical structure permeabilizes negatively charged vesicles but does not induce membrane fusion. The peptide in β-type conformation, on the other hand, permeabilizes neutral membranes and triggers fusion. As seen by31P NMR, the latter structure also exhibits the capacity to alter the lamellar organization of the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02442901
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