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  • 1
    Electronic Resource
    Electronic Resource
    The hypo-osmolarity-sensitive phenotype of the Saccharomyces cerevisiae hpo2 mutant is due to a mutation in PKC1, which regulates expression of β-glucanase (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 641-648 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell wall ; Protein kinase C ; β-Glucanase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To obtain more information about the cell wall organization of Saccharomyces cerevisiae, we have developed a novel screening system to obtain cell wall-defective mutants, using a density gradient centrifugation method. Nine hypo-osmolarity-sensitive mutants were classified into two complementation groups, hpo1 and hpo2. Phase contrast microscopic observation showed that mutant cells bearing lesions at either locus became abnormally large. A gene that complemented the mutant phenotype of hpo2 was cloned and sequenced. This gene turned out to be identical to PKC1, which encodes the yeast homologue of mammalian protein kinase C. Complementation tests with pkc1Δ showed that hpo2 is allelic to pkc1. To study the reason for the fragility of hpo2 cells, cell wall was isolated and the glucan was analyzed. The amount of alkali, acid-insoluble glucan, which is responsible for the rigidity of the cell wall, was reduced to about 30% that of the wild-type cell and this may be the major cause of the fragility of the hpo2 mutant cell. Analysis of total wall proteins in hpo2 mutant cells on SDS-polyacrylamide gels revealed that a 33 kDa protein was overproduced two- to threefold relative to the wild-type level. This 33 kDa protein was identified as a β-glucanase, encoded by BGL2. Disruption of BGL2 in the hpo2 mutant partially rescued the growth rate defect. This suggests that the PKC1 kinase cascade regulates BGL2 expression negatively and overproduction of the β-glucanase is partially responsible for the growth defect. Since the bgl2 disruption did not rescue the hypo-osmolarty-sensitive phenotype of the hpo2 mutant, PKC1 must negatively regulate other enzymes involved in the biosynthesis and metabolism of the cell wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283417
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  • 2
    Electronic Resource
    Electronic Resource
    Nonisothermal orientation-induced crystallization in melt spinning of polypropylene (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 2683-2697 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two kinds of polypropylene with different molecular weight (MI = 15 and 30) were melt-spun at the spinning temperatures of 210-290°C and take-up velocities of 0.15-3 km/min. In the cases of the spinning temperatures of 270 and 290°C for MI15 and 250 and 290°C for MI30, the density showed a minimum with increasing take-up velocity at around 0.5-1 km/min. This result suggests that crystallization behavior is influenced by two competitive effects, i.e., cooling rate and crystallization rate both of which are enhanced by the increase in take-up velocity. Crystal structures of slightly oriented monoclinic, slightly oriented pseudohexagonal, highly oriented pseudohexagonal, and highly oriented monoclinic were successively observed with increasing take-up velocity. The change of crystallization temperature may result in the different kinds of crystal modifications. Numerical calculations on nonisothermal orientation-induced crystallization in the melt spinning process and experimental results showed qualitative agreement in the change of crystallinity with take-up velocity, spinning temperature, and molecular weight.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370919
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  • 3
    Electronic Resource
    Electronic Resource
    Volume contraction and its significance in structural formation during the thermal stabilization of acrylic fibers (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1319-1326 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The length changes of acrylic fibers during isothermal treatment at temperatures from 208°C to 270°C were measured under constant tensile stresses. In order to elucidate the relation between the length and structural changes during heat treatment, the measurements of density, the elemental composition, and the aromatization index determined from X-ray diffraction were made for the fibers heat-treated at 252°C for various periods of time. It is shown that a contraction in length which accompanied a volume contraction occurred during extended heat treatment, even when the fibers were subjected to high tensile stresses. The volume contraction is attributed to the fact that planar cyclized polymer segments, formed by additional polymerization of the nitrile side groups, are built up and construct a stacking which is denser than the original fiber structure. The orientation of the stacking of the cyclized segments was measured for the fibers heat-treated in the fixed state giving a high orientation, which is comparable to that of the fibers heat-treated under a high tensile stress giving an extension to the fibers in the initial periods of heat treatment. These results were explained by considering the interaction of external constraint and volume contraction which occurs during heat treatment.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290425
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  • 4
    Electronic Resource
    Electronic Resource
    Polymorphic structure and physical properties of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate) (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 21 (1983), S. 275-284 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray diffraction studies of fibers of the polyester/ether poly(ethylene-1,2-diphenoxyethane-p,p′ -dicarboxylate) (PEET) produced by high-speed melt spinning show the existence of two polymorphic forms, designated α and β, in the solid state. The α form is obtained by annealing filaments melt spun at takeup speeds below 3000 m/min and is also found in samples crystallized from the melt and from dilute solutions. The α form has a monoclinic unit cell with dimensions a = 7.83, b = 10.33, c = 18.68 Å, and β = 83.1°. The equilibrium melting temperature and heat of fusion of the α form are 288.3°C and 19.1 cal/g, respectively. The β form predominates in highly oriented filaments obtained at takeup velocities above 6000 m/min. The unit cell is orthorhombic with dimensions a = 7.28, b = 5.65, and c = 18.64 Å. The β form does not transform to the α form on annealing.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.180210209
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