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  • 1
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    Piezoelectric Sensors (2007)
    Berlin, Heidelberg : Springer
    Details
    Keywords: Analytical biochemistry ; Biochemistry ; Biomedical engineering ; Chemical engineering ; Medical laboratories ; Physical optics
    ISBN: 9783540365686
    URL: https://doi.org/10.1007/b100347
    Language: English
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Micropatterned solid-supported membranes formed by micromolding in capillaries (2000)
    Springer
    European biophysics journal 29 (2000), S. 549-554 
    Details
    ISSN: 1432-1017
    Keywords: Microfluidic networks Micromolding in capillaries Scanning force microscopy Soft lithography Solid-supported membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract. The formation of individually addressable micropatterned solid-supported lipid bilayers has been accomplished by means of micromolding in capillaries. Small unilamellar vesicles were spread on glass slides to form planar supported membranes along microscopic capillaries molded as trenches into a polydimethylsiloxane (PDMS) elastomer. PDMS provides an elastic and transparent carrier for microcapillaries molded from silicon wafers displaying the desired inverse trenches. The so-called master structure has been conventionally etched into silicon by photolithography. The cured PDMS elastomer was briefly exposed to an oxygen plasma, rendering the surface hydrophilic, and subsequently attached to a glass surface in order to form hydrophilic capillaries equipped with flow-promoting pads on either side. One flowpad acts as a reservoir to be filled with the vesicle suspension, while the other one serves as a collector to ensure a sufficient capillary flow to cover the substrate completely. Formation of planar lipid bilayers on the glass slide along the capillaries was followed by imaging the flow and spreading of fluorescently labeled DMPC liposomes with confocal laser scanning microscopy. By means of scanning force microscopy in aqueous solution the formed lipid structures were identified and the height of the lipid bilayers was accurately determined. With both techniques, it was shown that the patterned bilayers remain separated and persist for several hours on the substrate in aqueous solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490000104
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes (1997)
    Springer
    European biophysics journal 26 (1997), S. 261-270 
    Details
    ISSN: 1432-1017
    Keywords: Key words Quartz crystal microbalance (QCM) ; Cholera toxin ; Tetanus toxin ; Pertussis toxin ; Solid supported membranes ; Gangliosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides GM1, GM3, GD1a, GD1b, GT1b and asialo-GM1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for GM1 (Ka = 1.8 ⋅ 108M–1), a lower one for asialo-GM1 (Ka = 1.0 ⋅ 107 M–1) and no affinity for GM3. The C-fragment of tetanus toxin binds to ganglioside GD1a, GD1b and GT1b containing membranes with similar affinity (Ka∼106 M–1), while no binding was observed with GM3. Pertussis toxin binds to membranes containing the ganglioside GD1a with a binding constant of Ka = 1.6 ⋅ 106 M–1, but only if large amounts (40 mol%) of GD1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to GD1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to GD1a.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050079
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  • 6
    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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  • 7
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    Size and mobility of lipid domains tuned by geometrical constraints (2017)
    National Academy of Sciences
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    Publication Date: 2017-07-10
    Description: In the plasma membrane of eukaryotic cells, proteins and lipids are organized in clusters, the latter ones often called lipid domains or “lipid rafts.” Recent findings highlight the dynamic nature of such domains and the key role of membrane geometry and spatial boundaries. In this study, we used porous substrates with different pore radii to address precisely the extent of the geometric constraint, permitting us to modulate and investigate the size and mobility of lipid domains in phase-separated continuous pore-spanning membranes (PSMs). Fluorescence video microscopy revealed two types of liquid-ordered (lo) domains in the freestanding parts of the PSMs: (i) immobile domains that were attached to the pore rims and (ii) mobile, round-shapedlodomains within the center of the PSMs. Analysis of the diffusion of the mobilelodomains by video microscopy and particle tracking showed that the domains’ mobility is slowed down by orders of magnitude compared with the unrestricted case. We attribute the reduced mobility to the geometric confinement of the PSM, because the drag force is increased substantially due to hydrodynamic effects generated by the presence of these boundaries. Our system can serve as an experimental test bed for diffusion of 2D objects in confined geometry. The impact of hydrodynamics on the mobility of enclosed lipid domains can have great implications for the formation and lateral transport of signaling platforms.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Structural and functional characterization of the two phosphoinositide binding sites of PROPPINs, a β-propeller protein family (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-07-02
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Adhesion and rupture of liposomes mediated by electrostatic interaction monitored by thickness shear mode resonators (2004)
    Springer
    Details
    Publication Date: 2004-03-05
    Print ISSN: 0175-7571
    Electronic ISSN: 1432-1017
    Topics: Biology , Physics
    Published by Springer
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  • 10
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    Nonlinear Loading-Rate-Dependent Force Response of Individual Vimentin Intermediate Filaments to Applied Strain (2017)
    American Physical Society
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    Publication Date: 2017-01-24
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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