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  • 1
    ISSN: 1573-6881
    Keywords: Black-lipid membrane ; ion fluxes ; oscillations ; phase transitions ; lipids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Oscillations in ion fluxes and membrane potential may be observed in cells and in mitochondria as well. We obtained Ca2+-induced oscillations in channel activity in black-lipid membranes reconstituted with hydrophobic components extracted from mitochondria. Mitoplasts prepared from purified rat liver mitochondria were extracted with ethanol followed by Folch extraction and further partial purification by silicic acid chromatography. Channel activity was measured in lipid bilayers formed from bovine brain lipids and 10% cardiolipin with addition of the purified tractions. The conductance with 10 mM Ca2+ was 100 pS or its multiples. Ca2+ gradients of 4 : 1 induced oscillating channel activity for several hours, with initial open states of 40 s and closed states of 56 s; the open times gradually decreasing to 8.6 s. No channel activity was seen without added fractions. The channel activity was associated with a Ca2+-binding lipid, nonpolar, low-molecular-weight fraction that in gel electrophoresis was not stained with Coomassie Blue and did not contain carbohydrate-staining material. 1H-Nuclear magnetic resonance spectra of the substance showed the presence of aliphatic chains and carbonyls, but the detailed structure remains to be elucidated.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Vegetation history and archaeobotany 5 (1996), S. 65-79 
    ISSN: 1617-6278
    Keywords: Late Neolithic ; Bronze Age ; Germany ; Prehistoric farming ; Cultural landscape
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract Botanical on-site and off-site data relating to Late Neolithic and Bronze Age settlement phases in south-western Germany are compared with a view to reconstructing economic and environmental change. The large differences between the Neolithic and Bronze Age as regards forest composition, crops and crop weeds, and charcoal input are explained in terms of different types of agronomic systems and hence cultural landscape. In the Late Neolithic, shifting cultivation, involving slash and burn, was practised with the result that the landscape was largely dominated by tall shrubs. In the Bronze Age there were more or less permanent arable fields with only short fallow phases. The agronomic system and the resulting cultural landscape was already similar to that of the medieval period and, especially, early medieval time.
    Type of Medium: Electronic Resource
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