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  • 1970-1974  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Künstliche Lipidfilme als Modelle biologischer Membranen (1970)
    Springer
    Naturwissenschaften 57 (1970), S. 474-480 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00593074
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  • 2
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1970)
    Springer
    Naturwissenschaften 57 (1970), S. 400-404 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599993
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  • 3
    Electronic Resource
    Electronic Resource
    Buchbesprechungen (1971)
    Springer
    Naturwissenschaften 58 (1971), S. 459-464 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00624629
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  • 4
    Electronic Resource
    Electronic Resource
    Valinomycin-mediated ion transport through neutral lipid membranes: Influence of hydrocarbon chain length and temperature (1973)
    Springer
    The journal of membrane biology 14 (1973), S. 339-364 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Stationary electrical conductance experiments together with nonstationary relaxation experiments allow a quantitative determination of rate constants describing carrier-mediated ion transport. Valinomycin-induced ion transport across neutral lipid membranes was studied. The dependence of the transport parameters on the chain length of the lipid molecules, on the kind of alkali ion, and on the temperature was determined. The relaxation time τ the current following a voltage jump shows a marked increase with decreasing temperature or with increasing chain length of the lipid molecules. This variation of τ is interpreted on the basis of a varying membrane fluidity. It is shown that under favorable circumstances the equilibrium constant of complex formation in the aqueous phase may be obtained from membrane experiments. Furthermore, the kinetics of exchange of valinomycin between membrane and water was studied. We found a marked influence of the totus surrounding the black film on the kinetics as well as on the total amount of valinomycin molecules in the membrane. The problem of location of the free carrier molecules inside the membrane is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868084
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  • 5
    Electronic Resource
    Electronic Resource
    Interaction of cytochromec with phospholipid monolayers and bilayer membranes (1971)
    Springer
    The journal of membrane biology 4 (1971), S. 74-86 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary For the study of the interaction between oxidized cytochromec and phosphatidylinositide, two different model systems were used: (1) monolayers which were deposited after the method of Langmuir and Blodgett onto glass plates, and (2) bimolecular (“black”) membranes in aqueous phase. The amount of bound protein was determined with a sensitive spectrophotometer. It was found that at low ionic strength about 1013 cytochromec molecules per cm2 are bound to the lipid surface, which nearly corresponds to a densely packed monolayer. At high ionic strength (∼ 0.1m) or low pH (pH〈3), the adsorbed protein layer becomes unstable. This result indicates that the interaction is mainly electrostatic. In accordance with this conclusion is the observation that the rate of adsorption is diffusion controlled; i.e., almost every protein molecule hitting the surface is bound. The cytochromec monolayer can be reduced by ascorbate. In contrast to ferrocytochromec in solution, the bound ferrocytochrome was found to be autoxidable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02431963
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  • 6
    Electronic Resource
    Electronic Resource
    Optical properties of artificial chlorophyll membranes (1971)
    Springer
    The journal of membrane biology 4 (1971), S. 284-294 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The composition and structure of lipid bilayer membranes containing chlorophylla have been studied with photometric and fluorometric methods. A sensitive double-beam spectrophotometer is described by which the pigment concentration in the bilayer can be determined. Up to 3×1013 chlorophyll molecules per cm2 can be incorporated into the membrane, corresponding to a mean distance of 20 Å between the porphyrin rings. At high chlorophyll concentrations, the absorption peaks are shifted toward longer wavelengths, indicating an interaction between porphyrin rings in the film. Parallel to the spectral shifts, a large decrease in the fluorescence quantum yield and a depolarization of the fluorescence are observed. These findings suggest that transfer of excitation energy takes place between neighboring chlorophyll molecules in the membrane. When an oxidating agent (K2S2O8) is added toone external phase, exactly half of the chlorophyll in the film is destroyed. This observation suggests that the chlorophyll molecules are localized in the membrane surfaces with the phytyl chains inserted into the hydrocarbon core of the membrane and the porphyrin rings facing the aqueous solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02431976
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  • 7
    Electronic Resource
    Electronic Resource
    Space charge-limited conductance in lipid bilayer membranes (1970)
    Springer
    The journal of membrane biology 3 (1970), S. 54-66 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A mathematical treatment is given for the flux of ions of one charge sign across lipid bilayer membranes. This treatment is a generalization of a previous analysis of the membrane conductance by D. Walz, E. Bamberg and P. Läuger which was restricted to systems with negligible space charge in the membrane. The present theory includes space charge effects, and it is no longer assumed that the electric field strength in the membrane is constant. It is found that the ohmic membrane conductivity λ0 is reduced by space charges; if only ions of one charge sign are soluble in the membrane, λ0 approaches a limiting value for increasing concentration of the permeable ion in the aqueous solution. The theory also predicts the range in which the constant field approximation is valid. It is found that space charge effects become predominant when the mean concentration of the permeable ion in the membrane exceeds 5×10−5 m. The currentvoltage characteristic of the membrane remains practically linear even in the presence of a high space charge. It is therefore concluded that the experimentally observed nonlinearity is caused mainly by the distortion of the potential energy profile of an ion due to image forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868006
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  • 8
    Electronic Resource
    Electronic Resource
    Channel formation kinetics of gramicidin A in lipid bilayer membranes (1973)
    Springer
    The journal of membrane biology 11 (1973), S. 177-194 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Previous studies have given evidence that the active form of gramicidin A in lipid bilayer membranes is a dimer which acts as an ion channel; it has been further shown that the mean lifetime of the channel strongly depends on the membrane thickness. As the thickness slightly decreases when a voltage is applied to the membrane, the equilibrium between conducting dimers and nonconducting monomers may be displaced by a voltage jump. From the relaxation of the electrical current after the voltage jump, information about the kinetics of channel formation is obtained. For a dioleoyllecithin/n-decane membrane the rate constant of association is found to be 2×1014 cm2 mole−1 sec−1, which is by three orders of magnitude below the limiting value of a diffusion-controlled reaction in a two-dimensional system. The dissociation rate constant is equal to 2 sec−1, a value which is consistent with the channel lifetime as obtained from electrical fluctuation measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869820
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  • 9
    Electronic Resource
    Electronic Resource
    Transport mechanism of hydrophobic ions through lipid bilayer membranes (1971)
    Springer
    The journal of membrane biology 5 (1971), S. 225-245 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Evidence is presented that the transport of lipid-soluble ions through bilayer membranes occurs in three distinct steps: (1) adsorption to the membranesolution interface; (2) passage over an activation barrier to the opposite interface; and (3) desorption into the aqueous solution. Support for this mechanism comes from a consideration of the potential energy of the ion, which has a minimum in the interface. The formal analysis of the model shows that the rate constants of the individual transport steps can be determined from the relaxation of the electric current after a sudden change in the voltage. Such relaxation experiments have been carried out with dipicrylamine and tetraphenylborate as permeable ions. In both cases the rate-determining step is the jump from the adsorption site into the aqueous phase. Furthermore, it has been found that with increasing ion concentration the membrane conductance goes through a maximum. In accordance with the model recently developed by L. J. Bruner, this behavior is explained by a saturation of the interface, which leads to a blocking of the conductance at high concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01870551
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  • 10
    Electronic Resource
    Electronic Resource
    Orientation of the porphyrin ring in artificial chlorophyll membranes (1972)
    Springer
    The journal of membrane biology 9 (1972), S. 177-194 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary A sensitive photometric method is described by which the dichroism of lipid bilayer membranes in aqueous phase can be measured. The method is applied to black films with incorporated chlorophylla andb. With chlorophylla a relatively large dichroism is found in the Soret band and a much weaker dichroism in the red band. From the experimental data, the angles β B and β R between the “blue” and “red” transition moments and the membrane can be obtained. β B and β R are then used to calculate the angle γ of the porphyrin ring with respect to the membrane surface. For chlorophylla and three different lipids, values of γ between 44 and 49° are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868051
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