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  • intercellular junctions  (3)
  • Chemical and chiroptical correlation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 122 (1991), S. 1097-1108 
    ISSN: 1434-4475
    Keywords: Circular dichroism ; Chemical and chiroptical correlation ; Enantioselective chromatography ; Torsional isomers and barriers ; X-ray crystal structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Titelverbindung2 wurde durch Hochdruckreaktion von 1,1′-Bianthryl mit Ethylen oder durch Kupplung von 1-Brom-9,10-dihydro-9,10-ethano-anthracen (4) als Mischung der Diastereomeren (Mesoform2a und Racemat2b) im Verhältnis von 1.5:1 bzw. 2.3:1 erhalten. Die konfigurative Zuordnung erfolgte sowohl aus den1H- und13C-NMR-Spektren als auch durch Kupplung von linksdrehendem4 zu (−)-2 b. Optisch aktives4 war durch enantioselektive Chromatographie an Triacetylcellulose in Ethanol optisch rein zugänglich. Seine Konfiguration wurde durch Umwandlung in die entsprechende Carbonsäure5 (bekannter Chiralität) als (+)(9R) [bzw. (−)(9S)] bestimmt. Damit war auch die Zentrochiralität im erwähnten Kupplungsprodukt (−)-(2b) als (9S)(9′S) festgelegt. Das Racemat2b ist eine Mischung von Rotameren im Verhältnis von 1.8:1. Die Rotationsbarriere wurde (in Abhängigkeit von der Temperatur) als ΔG#=92−95 kJ mol−1 sowohl durch1H-NMR-als auch CD-Kinetik (basierend auf der Äquilibrierung der getrennten optisch aktiven Rotameren vonracem.2) ermittelt. Für die letzteren können aufgrund der Annahme bevorzugter Konformationen auch die Symbole für die Axialchiralität vorgeschlagen werden. Für (−)-2b: (9S)(R)a(9′S) für das überpopulierte bzw. (−)-(9S)(S)a(9′S) für das unterpopulierte Rotamer. Diese Annahmen wurden durch Röntgenstrukturanalysen von2a und des Hauptrotamers von2b (mit Torsionswinkeln von −111.1 bzw. −121.2°) bestätigt.
    Notes: Summary The title compound2 was prepared either by highpressure reaction of 1,1′-bianthryl with ethylene or by coupling of 1-bromo-9,10-dihydro-9,10-ethanoanthracene (4). Both syntheses afforded a mixture of diastereoisomers (meso2a and racemate2b) in a ratio of 1.5:1 and 2.3:1, respectively. Configurational assignment was possible both from the1H- and13C-NMR spectra and by coupling of laevorotatory4 (accessibly by enantioselective chromatography on triacetyl cellulose in ethanol) to laevorotatory2b. (+)-4 was tranformed into the dextrorotatory carboxylic acid (+)-5 of known configuration (9R) thus establishing the configuration of (+)-4 as (9R) too and hence the centrochirality in (−)-2b as (9S)(9′S). The racemic form2b is a conformational (appr. 1.8:1) mixture of two rotamers. The rotational barrier was established as ΔG #=92−95 kJ mol−1 (depending on the temperature) both by1H-NMR and CD kinetics (based on equilibration of the separated optically active rotamers ofracem.2). For the latter preferred conformations were assumed allowing the assignment of the axial chirality: e.g. (−)-(9S)(R)a(9′S) for the main rotamer of (−)-2 b [and (−)(9S)(S)a(9′S) for the underpopulated one]. All assumptions were confirmed by X-ray crystal structure analyses of2 a and the main rotamer of2b with torsional angles around the 1,1′-bonds of −111.1 and −121.2°, respectively.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 23 (1992), S. 201-212 
    ISSN: 0886-1544
    Keywords: intercellular junctions ; desmosome ; assembly ; microtubules ; epithelia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Desmosomes, complex multisubunit structures that assemble at sites of cell-cell contact, are important components of the epithelial junctional complex. Desmosome assembly requires the coordinated interaction at the plasma membrane of at least 8 cytoplasmic and integral membrane proteins organized into two structurally and functionally distinct domains, the cytoplasmic plaque and membrane core. Previous studies (Pasdar et al., J. Cell Biol., 113:645-655) provided evidence that cytokeratin filaments and microtubules may regulate transfer and assembly of cytoplasmic plaque and membrane core proteins, respectively. To determine directly the role of microtubules in these processes, Madin-Darby canine kidney (MDCK) cells were treated with nocodazole or colchicine to disrupt the microtubular network. Biochemical analysis of the different components of the cytoplasmic plaque and membrane core domains revealed little or no effect of nocodazole or colchicine on the kinetics of synthesis, post-translational modifications, transfer of proteins to the plasma membrane or their metabolic stability in the presence or absence of cell-cell contact. Likewise, immunofluorescence analysis of desmosome formation demonstratedan apparently normal desmosome assembly in the presence of nocodazole or colchicine upon induction of cell-cell contact. These results indicate that an intact microtubular network is not necessary for the processing or transport of the desmosomal membrane core glycoproteins to the plasma membrane in the absence or presence of cell-cell contact. Furthermore, the integration of the cytoplasmic plaque and membrane core domains induced by cell-cell contact at the plasma membranes of adjacent cells does not require the presence of functional microtubules. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 163-180 
    ISSN: 0886-1544
    Keywords: intercellular junctions ; desmosome ; assembly ; MDCK ; epithelia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To investigate the possible role(s) of cytoskeletal elements in desmosome assembly we have studied the effects of cytostatic drugs on the assembly of desmosomes in MDCK epithelial cells. We showed previously [Pasdar et al.: Cell Motil. Cytoskeleton 23:201-213, 1992] that selective disruption of microtubules has no effect on desmosome assembly. Here, we have treated MDCK cells with cytochalasin B and a combination of cytochalasin B and nocodazole and analysed the effects on desmosome assembly. Immunofluorescence analysis of MDCK cultures following drug treatment indicated complete disruption of actin microfilaments and disorganization of cytokeratin intermediate filaments. Biochemical analysis of newly synthesized desmosomal membrane core glycoproteins as well as the cell adhesion proteir. E-cadherin revealed no effect of these drugs on the kinetics of synthesis, intracellular processing, or transport to the plasma membrane either in the presence or absence of cell-cell contact. However, morphological analyses revealed a significant disruption in the spatial organization of desmosomal proteins and E-cadherin. Drug treatment in the absence of cell-cell contact resulted in the disruption of the normally observed homogenous punctate staining pattern and appearance of aggregate staining. Induction of cell-cell contact in these cultures resulted in redistribution of some of the aggregate staining to the plasma membrane. In contrast to control cultures, significant amount of intracellular staining was retained for all desmosomal proteins. Biochemical analyses of turnover rates of newly synthesized desmosomal proteins indicated a significant decrease in metabolic stability of these proteins while the turnover rate of E-cadherin was not significantly different among control and drug-treated cultures. Taken together, these results suggest that intact actin and cytokeratin filaments are necessary for the stability, efficient assembly, and spatial organization of the junctional components at the membrane. The regulatory role of cytokeratins and actin filaments in assembly and stability of desmosomes on the plasma membrane is discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 108-121 
    ISSN: 0886-1544
    Keywords: intercellular junctions ; desmosome ; assembly ; kinase ; phosphatase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Desmosomes are one component of the intercellular junctional complex in epithelia. In cultures of epithelial cells, desmosome assembly can be regulated by modulating the calcium concentrations of the growth media. At present, very little is known about the intracellular signal transduction mechanisms that regulate desmosome assembly and disassembly in response to changing extracellular calcium concentrations. We have used inhibitors of protein kinases and phosphatases in a combined biochemical and morphological approach to analyze the role of protein phosphorylation in the assembly and disassembly of desmosomes in Madin-Darby canine kidney epithelial cells. Our results suggest that desmosomal proteins (desmoplakins I/II and desmoglein 1) are primarily phosphorylared on serine residues. Electron microscopic analyses of desmosome assembly upon induction of cell-cell contact, in the presence of protein kinase inhibitor, H-7, revealed an apparently normal assembly of desmosomes. However, complete disassembly of desmosomes was inhibited by H-7 upon removal of extracellular calcium. Under these conditions, although desmosomes split, desmosomal plaques and their associated cytokeratin filaments can not be internalized. In contrast, treatment of the cultures with okadaic acid (OA), an inhibitor of protein phosphatases, inhibited desmosome assembly but had no effect on disassembly. In addition, the inhibitory effect of okadaic acid on desmosome assembly was specific to this junction since we observed apparently normal tight junction and adherens junction in okadaic acid-treated cultures. These results suggest that via reversible protein phosphorylation involving both protein kinase and protein phosphatases. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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