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  • 11
    ISSN: 1573-5028
    Keywords: amylose-extender ; Ae ; genomic organization ; promoter analysis ; Zea mays L. ; starch-branching enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amylose-extender (Ae) gene encoding starch-branching enzyme IIb (SBEIIb) in maize is predominantly expressed in endosperm and embryos during kernel development. A maize genomic DNA fragment (−2964 to +20 485) containing the Ae gene was isolated and sequenced. The maize Ae mRNA is derived from 22 exons distributed over 16 914 bp. Twenty-one introns, differing in length from 76 bp to 4020 bp, all have conserved junction sequences (GT⋅⋅AG). Sequence analysis of the 5′- and 3′-flanking regions revealed a consensus TATA-box sequence located 28 bp upstream of the transcription initiation site as determined by primer extension analysis, and a putative polyadenylation signal observed 29 bp upstream of the polyadenylation site based on cDNA sequence. Genomic Southern blot analysis suggests that a single Ae gene is present in the maize genome. Promoter activity was confirmed by testing a transcriptional fusion of the Ae 5′-flanking region between −2964 and +100 to a luciferase reporter gene in a transient expression assay using maize endosperm suspension cultured cells. 5′ deletion analysis revealed that the 111 bp region from −160 to −50 is essential for high-level promoter activity.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In our continuing efforts to both (1) exploit the versatility of our unique emulsion based diimide hydrogenation technology and (2) expand the performance range of hydrogenated-SBR TPEs derived from this technology, we have investigated some of the physical and chemical effects of incorporating a polymer-bound antioxidant into HSBR. A polymerizable amine-type antioxidant was incorporated into the SBR structure using a conventional type “cold” emulsion polymerization recipe. For comparative purposes, unmodified and AO-modified SBRs were then “hydrogenated” in their latex forms by the diimide technique to approximately the same extent. Samples of the extracted, isolated polymers were evaluated by DSC techniques to ascertain any effects of the bound antioxidant. Additionally, latex cast films of the HSBRs were evaluated for their initial and aged physical properties. The results of these studies indicate that while hydrogenation of SBR into the 80-90% range does dramatically improve its resistance to oxidation compared with SBR (without antioxidant), a further substantial improvement in oxidation resistance can be obtained at the same hydrogenation level by the incorporation of a bound antioxidant. Furthermore, because the bound antioxidant molecule is too large to be incorporated into the polyethylene-like crystallites, it resides in the TPE's amorphous phase, where antioxidant protection is needed most, and does not appear to affect crystallite size, distribution, or overall initial TPE physical properties compared with the unmodified HSBRs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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