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  • Polymer and Materials Science  (152)
  • Biochemistry and Biotechnology  (16)
  • Avena  (5)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 9 (1965), S. 2811-2817 
    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: When hexaphenylcyclotrisilazane was heated above 450°C. at atmospheric pressure, it formed an infusible polymer of exceptional thermal and chemical stability. The polymerization, which was accompanied by elimination of benzene, is represented approximately by the equation: \documentclass{article}\pagestyle{empty}\begin{document}$\eta [({\rm C}_6 {\rm H}_5)_2 {\rm SiNH}]_3\,\, \to \,\,({\rm C}_6 {\rm H}_5 {\rm SiN})_{3n} + 3n{\rm C}_6 {\rm H}_6$\end{document} The infusible polymer was a foamed, vitreous, pale yellow solid with a high degree of stability to heat, acids, alkali, and organic solvents. A similar reaction occured with a resein that was obtained as a by-product in the preparation of hexaphenylcyclotrisilazane and with a mixture of silylamines that was obtained from the reaction of methylphenyldichlorosilane with ammonia. Coatings on aluminum and steel prepared by heating the silylamine polymers had good thermal stability and adhesion. Inclusion of a polymeric dimethylsilyl derivative of ethylenediamine improved the flexibility of the coatings.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Avena ; Cells (electric propeties) ; Electrical parameters ; Fusicoccin ; Plasmalemma ; Tonoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cytoplasm of subepidermal parenchyma cells of Avena sativa L. coleoptiles was collected at one end of the cell by centrifugation. The electrical properties of both plasmalemma and tonoplast were then examined with microelectrodes inserted into both cytoplasm and vacuole of the same cell. The input resistance of the cytoplasm measured with either electrode was 7.5±0.8 MΩ while that of the vacuole measured with the single vacuolar electrode and a bridge circuit was 29.2±3.1 MΩ. The latter value was not significantly different from that of control, uncentrifuged cells. The resistance of the tonoplast is therefore several times larger than the input resistance of the cytoplasm, but the specific resistance of the plasma membrane cannot be calculated without knowledge of the extent and pattern of intercellular coupling. Electrical coupling of the cytoplasms of adjacent cells was observed in only two out of eight experiments. The mean potential of the vacuoles,-77.8±6.4 mV, was not significantly different from that of the cytoplasm; however, all the available evidence indicates that variable tip potentials in impaled cells made absolute determination of the membrane potential uncertain. In fusicoccin, the cells hyperpolarized by 20 mV within 10 min. This reponse occurred entirely at the plasmalemma.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Planta 145 (1979), S. 437-442 
    ISSN: 1432-2048
    Keywords: Auxin ; Avena ; Cell elongation ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have compared the effects of cycloheximide (CHI) and two other rapid and effective inhibitors of protein synthesis, pactamycin and 2-(4-methyl-2,6-dinitroanilino)-N-methyl proprionamide (MDMP), on protein synthesis, respiration, auxin-induced growth and H+-excreation of Avena sativa L. coleoptiles. All three compounds inhibit protein synthesis without affecting respiration. The effectiveness of the inhibitors against H+-excretion and growth correlates with their ability to inhibit protein synthesis. Both CHI and MDMP inhibit auxin-induced H+-excretion after a latent period of 5–8 min, and inhibit growth after a 8–10-min lag. These results support the idea that continued protein synthesis is required in the initial stages of the growth-promoting action of auxin.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Planta 139 (1978), S. 43-45 
    ISSN: 1432-2048
    Keywords: Avena ; Cell elongation ; Fusicoccin ; Malate synthesis ; PEP carboxylase ; pH stat ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phytotoxin fusicoccin (FC) causes rapid synthesis of malate in coleoptile tissues, presumably via phosphoenolpyruvate (PEP) carboxylase coupled with malate dehydrogenase. The possibility that FC directly affects PEP carboxylase in Avena sativa L. and Zea mays L. coleoptiles was studied and rejected. The activity of this enzyme is unaffected by FC whether FC is added in vitro or a pretreatment to the live material. FC does not change the sensitivity of the enzyme to bicarbonate or malate. The activity of FC, instead, appears to be indirect. The pH sensitivity of PEP carboxylase is such that its activity, and thus the rate of malate synthesis, may be enhanced by an increase in cytoplasmic pH accompanying FC-induced H+ excretion. Since the enzyme is also particularily sensitive to bicarbonate levels, malate synthesis may also be enhanced by FC-induced uptake or generation of CO2.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Planta 148 (1980), S. 429-436 
    ISSN: 1432-2048
    Keywords: Auxin action ; Avena ; Coleoptile ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Synthesis of growth-limiting proteins (GLP) is required for continued auxin-induced elongation of oat (Avena sativa L.) coleoptiles. In order to determine whether GLP synthesis is dependent or independent of auxin, a double-labeling ratio technique, coupled with disc-gel electrophoresis, has been used to assess the effect of auxin on the pattern of protein synthesis. Sections were peeled to enhance amino-acid uptake; proteins were labeled with [14C]- or [3H] leucine in the presence or absence of indole-3-acetic acid for 40 min to 6 h, and were separated into soluble, membrane-associated, and wall-associated fractions. Regardless of the conditions used, or the protein fraction examined, no changes in response to auxin were detected in the pattern of protein synthesis. In order to escape detection by this technique an auxin-induced protein would have to comprise less than 0.75% of the total newly synthesized protein. Thus the synthesis of GLP appears to be independent of auxin. The same technique has been used to follow protein turnover. During the chase, proteins are initially degraded at an average rate of 8% h−1, and some protein bands showed as much as 14% h−1 degradation. No protein was detected which had a turnover rate as rapid as the GLP.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Planta 148 (1980), S. 429-436 
    ISSN: 1432-2048
    Keywords: Auxin action ; Avena ; Coleoptile ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Synthesis of growth-limiting proteins (GLP) is required for continued auxin-induced elongation of oat (Avena sativa L.) coleoptiles. In order to determine whether GLP synthesis is dependent or independent of auxin, a double-labeling ratio technique, coupled with disc-gel electrophoresis, has been used to assess the effect of auxin on the pattern of protein synthesis. Sections were peeled to enhance amino-acid uptake; proteins were labeled with [14C]- or [3H] leucine in the presence or absence of indole-3-acetic acid for 40 min to 6 h, and were separated into soluble, membrane-associated, and wall-associated fractions. Regardless of the conditions used, or the protein fraction examined, no changes in response to auxin were detected in the pattern of protein synthesis. In order to escape detection by this technique an auxin-induced protein would have to comprise less than 0.75% of the total newly synthesized protein. Thus the synthesis of GLP appears to be independent of auxin. The same technique has been used to follow protein turnover. During the chase, proteins are initially degraded at an average rate of 8% h−1, and some protein bands showed as much as 14% h−1 degradation. No protein was detected which had a turnover rate as rapid as the GLP.
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  • 7
    ISSN: 0887-3585
    Keywords: proteolytic cleavage ; immunological cross-reaction ; amber fragment ; temperature-sensitive mutant ; stationary growth-phase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Immunological cross-reaction was employed for identification of proteolytic fragments of E. coli RNA polymerase genered both in vitro and in vivo. Several species of partially denatured but assembled RNA polymerase were isolated, which were composed of fragments of the two large subunits, β and β′, and the two small and intact subunits, α and σ. Comparison of the rate and pathway of proteolytic cleavage in vitro of unassembled subunits, subassemblies, and intact enzymes indicated that the susceptibility of RNA polymerase subunits to proteolytic degradation was dependent on the assembly state.Using this method, degradation in vivo was found for some, but not all, of the amber fragments of β subunit in merodiploid cells carrying both wild-type and mutant rpoB genes. Although the RNA polymerase is a metabolically stable component in exponentially growing cells of E. coli, degradation of the full-sized subunits was found in two cases, i.e., several temperature-sensitive E. coli mutants with a defect in the assembly of RNA polymerase and the stationary-phase cells of a wild-type E. coli. The in vivo degradation of RNA polymerase was indicated to be initiated by alteration of the enzyme structure.
    Additional Material: 9 Ill.
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  • 8
    ISSN: 0887-3585
    Keywords: crystallization ; folate ; multifunctional ; twinning ; dehydrogenase ; cyclohydrolase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Methylenetetrahydrofolate([H4] folate) dehydrogenase (D) and methenyl[H4] folate cyclohydrolase (C) coexist as a bifunctional enzyme (DC) or as the amino-terminal domain of a trifunctional enzyme (DCS) where the third activity is 10-formyl[H4]lfolate synthetase (S). Two crystal forms of the DC domain of the human cytosolic DCS enzyme have been grown from polyethyleneglycol solution. The monoclinic P21 crystals diffract to 2.8 Å with a = 72.5 Å, b = 68.5 Å, c = 125.2 Å, and β = 91.8° but were found to be twinned. The orthorhombic P212121 crystals diffract to 2.5 Å with a = 67.7 Å, b = 135.9 Å, c = 61.6 Å, and contain two molecules per asymmetric unit. Proteins 26:479-480 © 1996 Wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 465-474 
    ISSN: 0887-3585
    Keywords: conformational search ; directed searches ; α-carbon coordinates ; modeling ; structure prediction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A directed conformational search algorithm using the program CONGEN (ref. 3), which samples backbone conformers, is described. The search technique uses information from the partially built structures to direct the search process and is tested on the problem of generating a full set of backbone Cartesian coordinates given only α-carbon coordinates. The method has been tested on six proteins of known structure, varying in size and classification, and was able to generate the original backbone coordinates with RMSs ranging from 0.30-0.87Å for the α-carbons and 0.5-0.99Å RMSs for the backbone atoms. Cis peptide linkages were also correctly identified. The procedure was also applied to two proteins available with only α-carbon coordinates in the Brookhaven Protein Data Bank; thioredoxin (SRX) and triacyiglycerol acylhydrolase (TGL). All-atom models are proposed for the backbone of both these proteins. In addition, the technique was applied to randomized coordinates of flavodoxin to assess the effects of irregularities in the data on the final RMS. This study represents the first time a deterministic conformational search was used on such a large scale. © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 2773-2787 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically active β-(1,1-dichloroethyl)-β-propiolactone (CH3CCl2-PL), β-(1,1-dichloropropyl)-β-propiolactone (C2H5CCl2-PL), and β-(1,1-dichlorobutyl)-β-propiolactone (C3H7CCl2-PL) were synthesized with enantiomeric excesses of 100, 100, and 84%, respectively. Polymerization was conducted in bulk and toluene solution, under vacuum, using mainly ZnEt2/H2O as initiator. Osmometry analyses indicate molecular weights in the range 10,000-25,000. The polymers thus prepared are semi-crystalline and show large optical rotation values.13 C-NMR was used to show that they have a high degree of isotacticity, indicating that little or no racemization occurs in the course of polymerization. Glass transition, melting and decomposition temperatures are given as a function of the size of the substituent, and their variations are discussed.
    Additional Material: 4 Ill.
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