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  • 1
    Electronic Resource
    Electronic Resource
    SYNTHETIC CELLS-SELF-ASSEMBLING POLYMER MEMBRANES AND BIOADHESIVE COLLOIDS (2001)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 31 (2001), S. 387-404 
    Details
    ISSN: 1531-7331
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We summarize developments in the construction of synthetic cells made from polymers, with a particular focus on mimicking the structure and behavior of blood cells. Two basic themes emerge-the use of block copolymers to make polmer vesicles and the functionalization of colloidal or polymeric microspheres with cell-like adhesive properties. Both platforms provide a means for building the complex hierarchy that is characteristic of biological cells, while also incorporating novel and perhaps superior properties of material strength, specific targeting, and controlled release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.matsci.31.1.387
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  • 2
    Electronic Resource
    Electronic Resource
    Lifetime of the P-selectin-carbohydrate bond and its response to tensile force in hydrodynamic flow (1995)
    [s.l.] : Nature Publishing Group
    Nature 374 (1995), S. 539-542 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SELECTINS tether to the blood vessel wall leukocytes that are flowing in the bloodstream and support subsequent labile rolling interactions as the leukocytes are subjected to hydrodynamic drag forces1,2. To support this rolling, selectins have been proposed to ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/374539a0
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  • 3
    Electronic Resource
    Electronic Resource
    Focal contact assembly through cytoskeletal polymerization: steady state analysis (1994)
    Springer
    Journal of mathematical biology 32 (1994), S. 677-704 
    Details
    ISSN: 1432-1416
    Keywords: Cell adhesion ; Focal contact ; Fibronectin ; Talin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract For many cell types, initial receptor-mediated attachment to a ligand-coated surface is followed by the formation of focal contacts - strong, specialized, discrete adhesive connections between cell and substrate in which receptors are clustered and simultaneously linked to extracellular ligand and cytoskeletal proteins. Since adhesion affects many aspects of cellular physiology including growth, differentiation, and motility, understanding the biochemical factors which regulate focal contact assembly should enhance our understanding of these phenomena. In this paper, we present a mathematical model to examine how receptor-ligand, receptor-cytoskeleton, and cytoskeleton-cytoskeleton interactions affect the formation of receptor clusters which serve as precursors to mature focal contacts. Receptor clustering is presumed to occur through self-recognition of cytoskeletal elements which induce the polymerization of ligand-receptor-cytoskeleton complexes. Polymerization only occurs when the ligand density is above a critical value and a decrease in the receptor-ligand affinity shifts the critical ligand density to higher values. While cytoskeletal protein expression and receptor-cytoskeleton affinity influence the concentration of monomeric complexes, the formation of polymeric ligand-receptor-cytoskeleton aggregates is most sensitive to changes in the self-association affinity between cytoskeletal proteins. We find that a 100-fold enhancement in the affinity between cytoskeletal elements can produce a substantial increase in the total fraction of adhesion receptors associated with focal contact precursors (from 5% to over 90%). Our results suggest that under physiological conditions, cellular control of focal contact assembly most likely occurs through modulation of specific cytoskeletal proteins to solidify cytoskeleton-cytoskeleton connections within precursor focal contact structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163022
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  • 4
    Electronic Resource
    Electronic Resource
    Centrifugation assay of IgE-mediated cell adhesion to antigen-coated gels (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 692-703 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adhesion of biological cells to substrates is often mediated by binding between cellular receptors and substrate-bound ligand. In this work, we used a centrifugation assay to measure the adhesion of rat basophilic leukemia (RBL) cells coated with immunoglobulin E (IgE) to substrates coated with the ligand dinitrophenol (DNP). Increasing force, decreasing DNP substrate density, and decreasing cell surface IgE density all led to decreasing adhesion. Experiments performed at low IgE cell surface densities, in which few tethers from between cell and substrate suggest individual tethers have a binding strength of 2 to 4 microdyne, in agreement with previous measurements of the force to uproot receptors from the plasma membrane. We use this system to show how subpopulations expressing different numbers of cell surface receptors may be separated by exploiting their differential adhesiveness to substrates.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400412
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  • 5
    Electronic Resource
    Electronic Resource
    A model of the binding, entry, uncoating, and RNA synthesis of Semliki Forest virus in baby hamster kidney (BHK-21) cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 485-496 
    Details
    ISSN: 0006-3592
    Keywords: Semliki Forest virus ; receptor ; trafficking ; attachment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A quantitative understanding of viral trafficking would be useful in treating viral-mediated diseases, designing protocols for viral gene therapy, and optimizing heterologous protein production. In this article, a model for the trafficking of Semliki Forest virus and its RNA synthesis in baby hamster kidney (BHK-21) cells is presented. This model includes the various steps leading to infection such as attachment, endocytosis, and viral fusion in the endosome. The model estimates a mean fusion time of 4 to 6 min for the wild-type virus, and 38 min for Fus-1, an SFV mutant which requires a lower pH for fusion. These mean fusion times are consistent with the time-scale of endosomal acidification, suggesting viruses fuse almost instantaneously with the endosomal membrane as soon as the pH of the endosome drops below the pH threshold of the virus. Infection is most likely controlled at the level of viral uncoating, as shown by the close agreement between the efficiency of uncoating and the experimentally determined fraction of viruses that is infectious. The viral RNA synthesized per cell is best described by assuming that it depends on the number of uncoated viruses prior to the onset of replication according to a saturation-type expression. A Poisson distribution is used to determine the distribution of uncoated viruses among the cells. Because attachment is the rate-limiting step in the uncoating of the virus, increasing the attachment rate can lead to enhanced RNA synthesis and, hence, new virion production. Such an increase in the attachment rate may be obtained by lowering the medium pH or the addition of a polycation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460513
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  • 6
    Electronic Resource
    Electronic Resource
    Kinetics of cell detachment: Effect of ligand density (1995)
    Springer
    Annals of biomedical engineering 23 (1995), S. 322-331 
    Details
    ISSN: 1573-9686
    Keywords: Cell Adhesion ; Ligand-Coated Substrate ; Peel Test ; Membrane Mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Cell adhesion to substratum is often mediated by binding between cell surface receptors and substrate ligands. Substrates can be derivatized with different types and densities of ligands, but how substrate chemistry determines cellular function, such as adhesion strength, has not been demonstrated quantitatively. We employ a numerical methodology developed by Dembo and colleagues (9), who investigated membrane peeling under conditions of excess ligand density, to investigate the kinetics and strength of cell peeling from ligand coated surfaces for arbitrary ligand density. We show there are two asymptotic limits to peeling strength, as quantified by the critical tension: a high ligand density limit, where the critical tension is independent of ligand density and depends logarithmically on the receptor density; and a low ligand density limit, in which the critical tension depends logarithmically on the ligand density but is independent of receptor density. In between these limits, we numerically determine the critical tension. The critical tension is always a weak function of the dissociation constant between ligand and receptor. Furthermore, we show how the rate of peeling, for tensions above the critical tension, depends on ligand density and the mechanical properties of the receptor-ligand bonds. Interestingly, we illustrate when small increases in ligand density should alter cellular behavior, inducing a change to spreading onto a substrate from peeling up from a substrate. In total the predictions of this paper provide criteria for the design of ligand-coated substrate that provide for the proper adhesion strength and dynamics of detachment of cells from surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000011
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  • 7
    Electronic Resource
    Electronic Resource
    Introduction: Cellular and tissue engineering (1995)
    Springer
    Annals of biomedical engineering 23 (1995), S. 207-207 
    Details
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000001
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  • 8
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    Onion-like glycodendrimersomes from sequence-defined Janus glycodendrimers and influence of architecture on reactivity to a lectin (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-01-19
    Description: A library of eight amphiphilic Janus glycodendrimers (GDs) with d-mannose (Man) headgroups, a known routing signal for lectin-mediated transport processes, was constructed via an iterative modular methodology. Sequence-defined variations of the Janus GD modulate the surface density and sequence of Man after self-assembly into multilamellar glycodendrimersomes (GDSs). The spatial mode of Man presentation is decisive for formation of either unilamellar or onion-like GDS vesicles. Man presentation and Janus GD concentration determine GDS size and number of bilayers. Beyond vesicle architecture, Man topological display affects kinetics and plateau level of GDS aggregation by a tetravalent model lectin: the leguminous agglutinin Con A, which is structurally related to endogenous cargo transporters. The agglutination process was rapid, efficient, and readily reversible for onion-like GDSs, demonstrating their value as versatile tools to explore the nature of physiologically relevant glycan/lectin pairing.
    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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    Exploring functional pairing between surface glycoconjugates and human galectins using programmable glycodendrimersomes (2018)
    National Academy of Sciences
    Details
    Publication Date: 2018-01-30
    Description: Precise translation of glycan-encoded information into cellular activity depends critically on highly specific functional pairing between glycans and their human lectin counter receptors. Sulfoglycolipids, such as sulfatides, are important glycolipid components of the biological membranes found in the nervous and immune systems. The optimal molecular and spatial design aspects of sulfated and nonsulfated glycans with high specificity for lectin-mediated bridging are unknown. To elucidate how different molecular and spatial aspects combine to ensure the high specificity of lectin-mediated bridging, a bottom-up toolbox is devised. To this end, negatively surface-charged glycodendrimersomes (GDSs), of different nanoscale dimensions, containing sulfo-lactose groups are self-assembled in buffer from a synthetic sulfatide mimic: Janus glycodendrimer (JGD) containing a 3′-O-sulfo-lactose headgroup. Also prepared for comparative analysis are GDSs with nonsulfated lactose, a common epitope of human membranes. These self-assembled GDSs are employed in aggregation assays with 15 galectins, comprising disease-related human galectins, and other natural and engineered variants from four families, having homodimeric, heterodimeric, and chimera architectures. There are pronounced differences in aggregation capacity between human homodimeric and heterodimeric galectins, and also with respect to their responsiveness to the charge of carbohydrate-derived ligand. Assays reveal strong differential impact of ligand surface charge and density, as well as lectin concentration and structure, on the extent of surface cross-linking. These findings demonstrate how synthetic JGD-headgroup tailoring teamed with protein engineering and network assays can help explain how molecular matchmaking operates in the cellular context of glycan and lectin complexity.
    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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  • 10
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    Bioactive cell-like hybrids coassembled from (glyco)dendrimersomes with bacterial membranes (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-02-16
    Description: A library of amphiphilic Janus dendrimers including two that are fluorescent and one glycodendrimer presenting lactose were used to construct giant dendrimersomes and glycodendrimersomes. Coassembly with the components of bacterial membrane vesicles by a dehydration–rehydration process generated giant cell-like hybrid vesicles, whereas the injection of their ethanol solution into PBS produced monodisperse nanometer size assemblies. These hybrid vesicles contain transmembrane proteins including a small membrane protein, MgrB, tagged with a red fluorescent protein, lipopolysaccharides, and glycoproteins from the bacteriumEscherichia coli. Incorporation of two colored fluorescent probes in each of the components allowed fluorescence microscopy to visualize and demonstrate coassembly and the incorporation of functional membrane channels. Importantly, the hybrid vesicles bind a human galectin, consistent with the display of sugar moieties from lipopolysaccharides or possibly glycosylated membrane proteins. The present coassembly method is likely to create cell-like hybrids from any biological membrane including human cells and thus may enable practical application in nanomedicine.
    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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