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  • 1
    Electronic Resource
    Electronic Resource
    Glycophorin-induced cholesterol-phospholipid domains in dimyristoylphosphatidylcholine bilayer vesicles (1991)
    s.l. : American Chemical Society
    Biochemistry 30 (1991), S. 4909-4916 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00234a011
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  • 2
    Electronic Resource
    Electronic Resource
    Chemically induced phase separation in mixed vesicles containing phosphatidic acid. Optical study (1975)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 97 (1975), S. 4114-4120 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00847a040
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  • 3
    Electronic Resource
    Electronic Resource
    On two-dimensional passive random walk in lipid bilayers and fluid pathways in biomembranes (1979)
    Springer
    The journal of membrane biology 48 (1979), S. 215-236 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The lateral mobility of pyrene, pyrene decanoic acid, and 1-palmitoyl-2-pyrene decanoyl-phosphatidyl choline (pyrene lecithin) in lipid bilayers is determined by the excimer formation technique. This method is applied to vesicles of lecithins differing in chain length and in the degree of saturation of the hydrocarbon chains. These values are compared with results in cephalins of different chain length and in dipalmitoyl phosphatidic acid at variable pH. The influence of cholesterol is investigated. The results are analyzed in terms of the Montroll model of two-dimensional random walk. The jump frequency of the probe molecule within the lipid lattice is obtained. The advantage of this measure of transport in lipid layers is that it does not involve lipid lattice parameters. The main results of the present work are: (i) The lateral mobility of a given solute molecule in lamellae of saturated lecithins is independent of hydrocarbon chain length and rather a universal function of temperature. (ii) In unsaturated dioleyl lecithin the amphiphatic molecules have lateral mobilities of the same size as in saturated lipids. The jump frequency of pyrene, however, is by a factor of two larger in the unsaturated lecithin. (iii) The jump frequencies in phosphatidyl ethanolamines are about equal to those in lecithins. (iv) In phosphatidic acid layers the hopping frequencies depend on the chargers of the head groups of both the lipids and the probes. (v) Cholesterol strongly reduces the jump frequency in fluid layers. (vi) The lateral mobility in biological membranes is comparable to that in artificial lipid bilayers. The experimental results are discussed in terms of the free volume model of diffusion in fluids. Good agreement with the predictions made from this model is found. A striking result is the observation of a tilt in dioleyl-lecithin bilayer membranes from the hopping frequencies of pyrene and pyrene lecithin. A tilt angle of ϕ-17° is estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872892
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  • 4
    Electronic Resource
    Electronic Resource
    Chain length and pressure dependence of lipid translational diffusion (1987)
    Springer
    European biophysics journal 14 (1987), S. 485-491 
    Details
    ISSN: 1432-1017
    Keywords: Lipid diffusion ; free volume ; excimers ; pressure ; model membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The translational diffusion of pyrene, pyrene butyric acid and pyrene decanoic acid has been determined in phosphatidylcholine bilayers of different chain length and under pressure up to 200 bars. In the liquid crystalline phase and at a given temperature the diffusion decreases with increasing chain length. At a constant reduced temperature, T red (about 10 K above the transition temperature), long chain lipids exhibit the fastest diffusion which is in disagreement with hydrodynamic models but favours free volume models for diffusion in lipid bilayers. The volume of activation, V act, calculated from the decrease of the diffusion coefficient with pressure, ∂ln D/∂P, depends on lipid chain length. V act decreases with decreasing lipid chain length at a given temperature, T=65°C, and increases at the reduced temperature. These results are again in agreement with the dependence of the diffusion on lipid chain length and therefore with the free volume model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293258
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  • 5
    Electronic Resource
    Electronic Resource
    Minor effects of bulk viscosity on lipid translational diffusion measured by the excimer formation technique (1988)
    Springer
    European biophysics journal 16 (1988), S. 109-112 
    Details
    ISSN: 1432-1017
    Keywords: Translational diffusion ; excimer formation ; glycerol ; interdigitated phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract We have investigated the effect of bulk viscosity on lipid translational diffusion using the excimer formation technique. In contrast to a study by Vaz et al. (1987), performed with the fluorescence recovery after photobleaching technique, we observed only a minor decrease of less than a factor of two for pyrene labelled phosphatidylcholine in glycerinated phosphatidylcholine bilayer membranes compared to an aqueous dispersion. Even the diffusion of pyrene labelled gangliosides with an oligosaccharide head-group that protrudes from the membrane surface is not strongly restricted by the increased bulk viscosity. We conclude that the viscosity of the fluid bounding the lipid bilayers is of minor importance for the diffusion of membrane lipids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00255520
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  • 6
    Electronic Resource
    Electronic Resource
    Cell adhesion monitoring using a quartz crystal microbalance: comparative analysis of different mammalian cell lines (1998)
    Springer
    European biophysics journal 28 (1998), S. 26-37 
    Details
    ISSN: 1432-1017
    Keywords: Key words Quartz crystal microbalance ; Cell adhesion ; Cell-substrate interaction ; RGD-sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The quartz crystal microbalance (QCM) has been widely accepted as a sensitive technique to follow adsorption processes in gas as well as in liquid environments. However, there are only a few reports about the use of this technique to monitor the attachment and spreading of mammalian cells onto a solid support in culture. Using a QCM-setup we investigated the time course of cell attachment and spreading as a function of seeding density for three widespread and frequently used cell lines (MDCK strains I and II and Swiss 3T3-fibroblasts). Results were found to be in good agreement with the geometrical properties of the individual cell types. The shifts of the resonance frequency associated with confluent cell layers on top of the quartz resonators were found to be dependent on the cell species [MDCK-I: (320±20) Hz; MDCK-II: (530±25) Hz; 3T3: (240±15) Hz] reflecting their individual influence on the shear oscillation of the resonator. These findings are discussed with respect to the basic models of materials in contact with an oscillating quartz resonator. We furthermore showed by inhibition-assays using soluble RGD-related peptides, that only specific, integrin mediated cell adhesion is detected using this QCM approach, whereas the sole presence of the cellular body in close vicinity to the resonator surface is barely detectable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050180
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of lateral motion of glycophorin a reconstituted in liposomes of dimyristoylphosphatidylcholine (1981)
    Springer
    European biophysics journal 7 (1981), S. 307-307 
    Details
    ISSN: 1432-1017
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02425438
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  • 8
    Electronic Resource
    Electronic Resource
    Polymyxin binding to charged phospholipid bilayer membranes: A cooperative lipid-protein-interaction (1981)
    Springer
    European biophysics journal 7 (1981), S. 322-322 
    Details
    ISSN: 1432-1017
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02425453
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  • 9
    Electronic Resource
    Electronic Resource
    Double-mode impedance analysis of epithelial cell monolayers cultured on shear wave resonators (1996)
    Springer
    European biophysics journal 25 (1996), S. 93-103 
    Details
    ISSN: 1432-1017
    Keywords: Key words Impedance analysis ; MDCK-cells ; Quartz crystal microbalance (QCM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The viscoelastic behavior of epithelial cells (MDCK-I and MDCK-II) grown on AT-cut quartz crystals with a fundamental resonance at 5 MHz was investigated by impedance spectroscopy. Using the electromechanical model recently derived by Martin et al. [(1991) Anal Chem 63: 2272 – 2281] for Newtonian liquids in contact with shear wave resonators we quantified the viscous damping arising from the adherent cells by fitting the impedance data with a modified Butterworth-Van Dyke circuit in the region of the resonance frequency. Impedance spectroscopy was additionally performed in the frequency range from 1 Hz to 1 MHz to scrutinize the passive electrical properties of the epithelial cell layers using an additional platinum electrode. These data allow one to document the cell layers' integrity as well as the electrode coverage. We were able to confirm that the presence of a cell-layer mainly increases damping of the shear wave and does not exhibit a pure mass-load behavior. These findings were supported by the discovery that the inductance L in the electromechanical model was less influenced by the cell-layer than the resistance R. The apparent cell-viscosities determined by our method are 0.097 poise for MDCK-I and 0.142 poise for MDCK-II cell-layers. These low apparent viscosities may be explained in terms of a considerable spacing between the cells immobilized via their focal contacts and the quartz surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050021
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  • 10
    Electronic Resource
    Electronic Resource
    Specific binding of peanut agglutinin to GM1-doped solid supported lipid bilayers investigated by shear wave resonator measurements (1996)
    Springer
    European biophysics journal 25 (1996), S. 105-113 
    Details
    ISSN: 1432-1017
    Keywords: Key words Quartz crystal microbalance (QCM) ; Impedance spectroscopy ; Solid supported lipid bilayers ; Lectins ; Gangliosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract This study deals with the specific interaction between the lectin peanut agglutinin (PNA) from Arachis hypogaea and the ganglioside GM1 which was incorporated in a solid supported lipid bilayer immobilized on a gold electrode placed on top of an AT-cut quartz crystal. Bilayer formation was reached by self-assembly processes. The first monolayer consists of octanethiol attached to the gold surface via chemisorption and the second monolayer was immobilized by vesicle fusion on the preformed hydrophobic surface. We managed to keep unspecific binding to a minimum by using a phospholipid matrix consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Lectin binding to ganglioside GM1 containing membranes was determined by a decrease of the resonant frequency of the quartz crystal. The minimum amount of receptor within the membrane which is necessary to obtain a complete protein monolayer was found to be less than 2 mol%. The adsorption isotherm of PNA to GM1 was recorded and analyzed to be of Langmuir type, exhibiting a binding constant of PNA to the ganglioside of 8.3 ⋅ 105 M–1. The good agreement of the calculated Langmuir adsorption isotherm with the obtained experimental data implies that protein multilayers are not formed and that interactions between the adsorbents can be neglected. Furthermore, the association constants of two different saccharides, β-Galp-(1 → 3)-GalNAc exhibiting a strong binding to PNA in solution, and β-D-galactose with a much lower affinity were estimated by determining the equilibrium concentration of PNA attached to the surface. Moreover we were able to remove the attached lectin monolayer by digestion of the protein with pronase causing an increase in the resonant frequency which almost reversed the frequency shift to lower frequencies during adsorption. An even more complex system was built up by the use of digoxigenin-labeled PNA which also binds to the solid supported membrane containing the receptor GM1. The immobilized lectin was recognized by anti-digoxigenin-Fab-fragments, which is measurable by a further decrease of the resonant frequency. For all binding processes we found larger frequency shifts for a complete protein monolayer than predicted by Sauerbrey's equation, clearly showing that in addition to mass loading viscoelastic changes occur at the lipid-protein interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050022
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