Publications (8)44.64 Total impact
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Article: Functional expression of Ca²⁺ dependent mammalian transmembrane gap junction protein Cx43 in slime mold Dictyostelium discoideum.
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ABSTRACT: In this paper, we expressed murine gap junction protein Cx43 in Dictyostelium discoideum by introducing the specific vector pDXA. In the first step, the successful expression of Cx43 and Cx43-eGFP was verified by (a) Western blot (anti-Cx43, anti-GFP), (b) fluorescence microscopy (eGFP-Cx43 co-expression, Cx43 immunostaining), and (c) flow cytometry analysis (eGFP-Cx43 co-expression). Although the fluorescence signals from cells expressing Cx43-eGFP detected by fluorescence microscopy seem relatively low, analysis by flow cytometry demonstrated that more than 60% of cells expressed Cx43-eGFP. In order to evaluate the function of expressed Cx43 in D. discoideum, we examined the hemi-channel function of Cx43. In this series of experiments, the passive uptake of carboxyfluorescein was monitored using flow cytometric analysis. A significant number of the transfected cells showed a prominent dye uptake in the absence of Ca(2+). The dye uptake by transfected cells in the presence of Ca(2+) was even lower than the non-specific dye uptake by non-transformed Ax3 orf+ cells, confirming that Cx43 expressed in D. discoideum retains its Ca(2+)-dependent, specific gating function. The expression of gap junction proteins expressed in slime molds opens a possibility to the biological significance of intercellular communications in development and maintenance of multicellular organisms.Biochemical and Biophysical Research Communications 02/2012; 419(2):165-9. · 2.48 Impact Factor -
Article: Quantitative evaluation of mechanosensing of cells on dynamically tunable hydrogels.
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ABSTRACT: Thin hydrogel films based on an ABA triblock copolymer gelator [where A is pH-sensitive poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) and B is biocompatible poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC)] were used as a stimulus-responsive substrate that allows fine adjustment of the mechanical environment experienced by mouse myoblast cells. The hydrogel film elasticity could be reversibly modulated by a factor of 40 via careful pH adjustment without adversely affecting cell viability. Myoblast cells exhibited pronounced stress fiber formation and flattening on increasing the hydrogel elasticity. As a new tool to evaluate the strength of cell adhesion, we combined a picosecond laser with an inverted microscope and utilized the strong shock wave created by the laser pulse to determine the critical pressure required for cell detachment. Furthermore, we demonstrate that an abrupt jump in the hydrogel elasticity can be utilized to monitor how cells adapt their morphology to changes in their mechanical environment.Journal of the American Chemical Society 02/2011; 133(5):1367-74. · 9.91 Impact Factor -
Article: Native supported membranes on planar polymer supports and micro-particle supports.
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ABSTRACT: To bridge soft biological materials and hard inorganic materials is an interdisciplinary scientific challenge. Despite of experimental difficulties, the deposition of native biological membranes on supports is a straightforward strategy. This review provides an overview of advances in the fabrication and characterization of native biological membranes on planar polymer supports and micro-particles.Journal of Structural Biology 07/2009; 168(1):137-42. · 3.41 Impact Factor -
Article: Covalent modification of chitin with silk-derivatives acts as an amphiphilic self-organizing template in nacre biomineralisation.
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ABSTRACT: Molluscs have a well-deserved reputation for being expert mineralizers of various shell types such as nacre. Nacre is defined as regularly arranged layers and stacks of approximately 0.5 microm thick aragonite platelets that are extracellularly formed within a complex mixture of organic matrix. The control of species-specific layer thickness by the animal is still enigmatic. Despite the recent findings on the periodic layer-by-layer structures of chitin layers and silk-like protein layers in nacre-type biominerals, little is known about how the interface is defined between two different layers. In this paper, we demonstrate the presence of covalently attached, hydrophobic amino acid side chains in the chitin matrix in the bivalve mollusc Mytilus galloprovincialis by the combination of infrared spectroscopy and mass spectroscopy. The accumulation of the modified chitin matrix at the interface is quantified by the critical aggregate concentration of the purified chitin matrix, which is approximately an order of magnitude smaller than that of pure chitin. Our finding suggests an active role of such chemically modified chito-oligosaccharides in the creation of a defined interface and guidance of the periodic matrix textures, which would result in unique material properties of natural mollusc shells.Journal of Structural Biology 05/2009; 167(1):68-75. · 3.41 Impact Factor -
Article: Native supported membranes: creation of two-dimensional cell membranes on polymer supports (Review).
Biointerphases 06/2008; 3(2):FA12. · 2.21 Impact Factor -
Article: Quantitative in vitro biopolymerization to chitin in native chitosomal membranes supported by silica microparticles.
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ABSTRACT: To investigate the unknown physical mechanisms of chitin biosynthesis quantitatively, we designed a quantitative in vitro biopolymerization assay by deposition of native chitosomal membranes from Saccharomyces cerevisiae onto solid silica microparticles of a defined size (ø = 3 microm). The homogeneous coating of particle surfaces with native chitosomal membranes observed by confocal microscopy agrees well with the surface coverage calculated by the phosphate analysis. The amount of the synthesized chitin polymers is determined by radioactive assays, which demonstrate that chitin synthase in particle-supported membranes retains its specific enzymatic activity. In comparison to planar substrates, particle supports of defined size (and thus surface area) enable us to amplify the signals from immobilized proteins owing to the much larger surface area and to the capability of concentrating the sample to any given sample volume. Moreover, the large density of particle supports offers unique advantages over purified chitosomes in the quick separation of particle-supported membranes and materials in bulk within 1 min. This allows for the termination of the polymerization reaction without the disruption of the whole membranes, and thus the chitin polymers released in bulk can quantitatively be extracted. The obtained results demonstrate that the native biological membranes on particle supports can be utilized as a new in vitro biopolymerization assay to study the function of transmembrane enzyme complexes.Journal of the American Chemical Society 10/2007; 129(35):10807-13. · 9.91 Impact Factor -
Article: Selective deposition of native cell membranes on biocompatible micropatterns.
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ABSTRACT: We establish two methods to deposit native biomembranes (human erythrocyte membranes and sarcoplasmic reticulum membranes) selectively onto biocompatible microtemplates. The first method utilizes UV photolithography to micropattern the regenerated cellulose, while the second uses the "stamping" of protein barriers onto homogeneous cellulose supports. The relatively simple methods established here allow for the position selective spreading of three-dimensional native cells into two-dimensional films, retaining the orientation and lateral density of transmembrane proteins in their native state.Journal of the American Chemical Society 04/2004; 126(10):3257-60. · 9.91 Impact Factor -
Article: Cell adhesion onto highly curved surfaces: one-step immobilization of human erythrocyte membranes on silica beads.
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ABSTRACT: This paper deals with single-step, orientation-selective immobilization of human erythrocyte membranes on bare silica beads with different topographies: 1) solid (nonporous) silica beads with a diameter of 3 microns and 2) porous silica beads with a diameter of 5 microns. Erythrocyte membranes were immobilized onto beads simply by incubation, without sonication or osmotic lysis. Membrane orientation before and after immobilization was identified with two immunofluorescence labels: 1) the extracellular part of glycophorin can be labeled with a first monoclonal antibody and a second polyclonal antibody with fluorescence dyes (outside label), while 2) the cytoplasmic domain of Band 3 can be recognized with a first monoclonal antibody and a second fluorescent polyclonal antibody (inside label). Adherent erythrocytes on the beads all ruptured, inverted the asymmetric orientation of the membrane, and selectively exposed their cytoplasmic domain. The surface topography did not influence the orientation or the amount of immobilized membrane. On the other hand, the fact that no adsorption or rupture of erythrocytes could be observed on planar quartz substrates suggests a significant influence of contact curvature on adhesion energy.ChemPhysChem 08/2003; 4(7):699-704. · 3.41 Impact Factor
Top co-authors
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Institutions
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2007–2012
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Universität Heidelberg
- Institute of Physical Chemistry
Heidelberg, Baden-Wuerttemberg, Germany
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2009
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INM – Leibniz-Institut für Neue Materialien gGmbH
Saarbrücken, Saarland, Germany
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2004
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Technische Universität München
- Lehrstuhl für Biophysik (E22)
München, Bavaria, Germany
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