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  • 1
    Electronic Resource
    Electronic Resource
    Plant viral leaders influence expression of a reporter gene in tobacco (1993)
    Springer
    Plant molecular biology 23 (1993), S. 97-109 
    Details
    ISSN: 1573-5028
    Keywords: cauliflower mosaic virus ; β-glucuronidase ; 35S promoter ; tobacco mosaic virus ; translation efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to optimise expression of a foreign protein in transgenic plants we investigated the potential benefits of including a viral untranslated leader sequence within a plant transformation vector. A variety of 5 leaders, including the tobacco mosaic virus (TMV) leader sequence and 31 nucleotides of the cauliflower mosaic virus (CaMV) 35S RNA leader, were compared. Viral leader constructs employing the 35S promoter and the reporter β-glucuronidase (GUS) were tested by electroporation into tobacco mesophyll protoplasts and against a cointroduced chloramphenicol acetyl transferase (CAT) gene in transgenic tobacco leaves. In the transient assay system, GUS activities from the viral leaders were compared with those from either a short, random leader or a translational fusion of the CaMV 19S RNA ORF VI to GUS. A two-to-three-fold enhanced level of expression resulted when these leaders were substituted with either the 35S RNA or the TMV leader sequences. This enhancement was further increased, to four-to five-fold, by inclusion of four or seven of the bases from the 35S transcription initiation site adjacent to the TMV leader. In transgenic tobacco the improved GUS levels were maintained from constructs including either the TMV leader (eight-fold) or this sequence with the addition of the 35S transcription initiation site bases (ten-fold). A comparison of GUS enzyme amounts with GUS mRNA amounts, using the CAT gene as an internal standard, revealed that TMV leader-bearing mRNA was translated from four-to six-fold more efficiently than the random leader control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00021423
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  • 2
    Electronic Resource
    Electronic Resource
    Copolymers of ethylene with norbornene derivatives - dynamic mechanical properties (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 1607-1618 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic mechanical properties have been determined and the β relaxation temperatures Tβ have been located for a series of copolymers of ethylene with norbornene, methylnorbornene, dicyclopentadiene, and octahydrodimethanonaphthalene. The Tβ values show discontinuous changes with changing comonomer content. The several levels of Tβ observed apparently can be associated with the sequence of close multiplets of norbornane moieties ranging from isolated units through pairs to triads and higher. For isolated norbornane units Tβ is around 10°C, while for pairs of these units, probably separated by a C2H4 unit, it is 55°C. The size of the norbornene-type comonomer has a small but measurable effect on these values of Tβ. The bearing of these results on the problem of defining a value of Tg for polyethylene is discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120809
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  • 3
    Electronic Resource
    Electronic Resource
    Low-molecular-weight species from high-pressure polyethylene (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2511-2527 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A partial analysis is given of the low-molecular-weight “oil” fraction produced in the high-pressure free-radical-initiated polymerization of ethylene. These oils are shown to constitute a separate family of compounds whose molecular weight distribution can be clearly distinguished from that of the remainder of the polymer. The mechanisms of formation of oils as a class, and of individual compounds found in the oil fraction, are discussed in some detail. The structures of the oils are used to inter steps in the mechanism of polymerization that lead to the formation of short-chain branches and unsaturation. It is concluded that the data are consistent with the extended Roedel mechanism with the provisions that (1) secondary radicals are probable products of radical scission, (2) cyclic intermediates of other than six members lead to the formation of three, five, and possibly six carbon branches, and (3) clusters of ethyl groups separated by single methylene groups are unlikely side chains.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.170170824
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  • 4
    Electronic Resource
    Electronic Resource
    Modification of an epichlorohydrin polymerization (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 645-656 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The acid-catalyzed polymerization of epichlorohydrin was modified by the addition of 1,4-butanediol diglycidyl ether to the reaction. The amount of diepoxide added and the method of addition were varied to produce a series of polymers with increased molecular weight, broad molecular weight distributions, and variations in hydroxyl functionality. Polyurethane networks were prepared from these polyols for the evaluation of elastomeric properties. The most obvious result was the lack of elastomeric network formation in the unmodified material when modified polyols produced elastomeric properties under the same conditions. Differences in properties between samples with more diepoxide added in the original polymerization generally showed trends to lower elongation and higher modulus. Changes in the method of addition of the diepoxide produced great differences in the toughness of the elastomers formed in the cure process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.170220314
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