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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 2127-2137 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new method of polymerization of the N-carboxy anhydride (NCA) of glutamic acid is presented by which poly(glutamic acid) is obtained directly from the NCA without protecting its carboxyl group. The principle underlying is that by adjusting the mole ratio of the initiator butylamine, [I], to the monomer, [A], butylamine can be used as protecting agent for the carboxyl group of the NCA so that the rest of butylamine acts as initiator in the heterogeneous polymerization in acetonitrile. Quantitative conversion was obtained for an [A]/[I] ratio of 1. In analogy to other heterogeneous polymerizations of NCAs in acetonitrile, this is due to the formation of the helix during polymerization, which was confirmed by IR absorption and X-ray diffraction measurements. As the [A]/[I] ratio increases, the conversion, the helix content of the resultant polymer, and the amount of butylamine combined with it decrease drastically. It is suggested that “copolymerization” of the amine-protected and unprotected NCAs occurs, giving rise to a partially helical chain, whose contents of the amine-protected side chains and accordingly of the helix are the higher the smaller the [A]/[I] ratio.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 174 (1982), S. 25-39 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although the cells in tissues are known to be motile under special conditions (e.g., during tissue turnover or wound healing), there are not many reports that polygonal cells covering an area without leaving any gaps are also capable of movement. In the present study, cell movements (cell shifting and rearrangement) in a living mammalian eye tissue were documented by identifying and locating individual cells over intervals as long as 100 days. Cat corneal endothelium, a monolayered cell sheet, was wounded by removing a small number (about 180) of endothelial cells from the internal lining of the cornea. Healing of the wounded tissue was observed with a wide-view specular microscope applied to the outer surface of the cornea, enabling us to identify individual cells for as long as two to three months.Cells surrounding the wound underwent areal enlargement, elongated toward the wound, and shifted to cover the wound surface. During days 4-7, cells became rearranged by changing neighbors in such a way that they retained their enlarged size but recovered their non-elongated, original shape. This pattern of cell rearrangement was interpreted by a computer simulation which assumed that cells shorten their boundary length while maintaining contacts with contiguous cells. After day 7, the enlarged cells adjacent to the wounded area gradually contracted and pulled surrounding cells toward the wounded area. These movements were followed by a temporary halt in cell shifting, then by a recovery of shifting and cell elongation. These movements are interpreted as a result of the contractility of endothelial cell microfilaments.
    Additional Material: 14 Ill.
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and conformational analysis of (3′R)-3-hydroxyleurosidine (5), (3′S)-3-hydroxyleurosidine (10), (3′S)-3-acetoxy-4′-deoxyleurosidine (15), (3′R)-3-acetoxy-4′-deoxyleurosidine (23), (3′R)-3-acetoxy-4′-deoxyvinblastine (16), (3′S)-3-acetoxy-4′-deoxyleurosidine (28) is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cell-free systems from Catharanthus roseus plants are utilized for various studies relating to the biosynthesis of indole alkaloids. Tryptamine (5) and secologanin (6), two fundamental building units, are shown to be incorporated into the alkaloid vindoline (7). In another study, catharanthine (18) and vindoline (7) are utilized by this enzyme system and coupled to the important bisindole biointermediate 3′,4′-anhydrovinblastineThe previously [20] used name for 17, 3′, 4′-dehydrovinblastine, is incorrect. (17). The latter substance is, in turn, incorporated and converted to the natural alkaloids leurosine (8), Catharine (9) and vinblastine (10), thereby providing information about the biosynthesis of these complex molecules. High pressure liquid chromatography assay of the enzymic mixture sheds light on the enzymes involved in the coupling of 18 and 7.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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