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  • Physics  (3)
  • Column liquid chromatography  (2)
  • 35S promoter  (1)
  • 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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A particle size distribution analysis of stressed HPLC column packing material (1991)
    Springer
    Chromatographia 31 (1991), S. 362-366 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Particle size distribution ; Stationary phase stress ; Silica gel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A particle size distribution analysis has been completed on three different HPLC column packing materials including silica gel (Si60) and two bonded phases (RP8 and RP18). The stationary phases were subjected to 18 hours stress with 1 N or 3 N KOH and found to have quantitatively different distribution patterns initially, at 13 hours and finally at 18 hours although the average particle diameters for the Si60 and RP8 were the same or higher at 18 hours as initially. Thirteen hoursstress with sodium octanesulfonate, tetrabutylammonium phosphate and ammonium acetate at exaggerated conditions also resulted in distributional changes with the Si60 and RP8 decreasing in average particle diameter when exposed to ammonium acetate and tetrabutylammonium stressing respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262193
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  • 3
    Electronic Resource
    Electronic Resource
    A particle size distribution analysis of used HPLC column packing material (1993)
    Springer
    Chromatographia 35 (1993), S. 295-301 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Used column packings ; Particle size distribution ; Scanning electron microscopy ; Column age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular progressions between the two extremes through the column. A new ODS-3 column showed log-normal size distributions from the inlet to the outlet ends. Spherical silica based column particle size distributions showed distinct shoulders on large central distribution peaks in most column sections with various degrees of shoulder erosion. The spherical resin based column showed a broader inlet particle size distribution progressing to a very narrow outlet distribution. SEMs of both irregular and spherical silica based columns revealed a larger number of undersized particles and debris at the outlet than inlet ends which could have resulted from stationary phase degradation, since this was not seen in the new ODS-3 column. While several SEMs of the spherical silica based columns revealed hollow spheres and twins, the spherical resin based column packing showed stress fractures or wrinkle lines resulting from use or dehydration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277513
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  • 4
    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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  • 5
    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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    Paper (German National Licenses)
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  • 6
    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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