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  • AERODYNAMICS
  • Cell & Developmental Biology
  • Organic Chemistry
  • 1990-1994
  • 1985-1989  (2)
  • 1987  (2)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 232-236 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Enantionselective Synthesis of L-ThreonineAn enantioselective synthesis of L-threonine (1) is described. Racemic ethyl 2-acetamido-3-oxobutyrate (6) was synthesized from ethyl acetoacetate (2) [4][5] and then transformed to the epimeric optically active alcohols 7a and 7b by microbiological reduction with Saccharomyces rouxii. The Mixture 7a/7b could be converted to 1 by slightly modified, known Methods in a yield of ca. 52% with respect to 7a/7b.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 18 (1987), S. 267-278 
    ISSN: 0148-7280
    Keywords: micro puncture ; fractionation ; viscosity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Rat cauda epididymidal spermatozoa are kept quiescent in the cauda lumen by a protein fraction termed “immobilin”, but it has not been shown whether or not this activity is unique to the immobilin fraction. Cauda fluid was subjected to gel filtration chromatography and the eluents contributing to three peaks of absorbance at A280 were pooled, lyophylized, and reconstituted at equivalent concentrations. Their relative viscoelasticity and their effects on sperm motility were determined. Peak 1 (P1), containing proteins 〉 400 kd, retained the greatest sperm-immobilizing activity, but P2 and P3 also had sperm-immobilizing activity related to their viscoelasticity. P1 and an immobilin fraction obtained by ultracentrifugation of rat cauda fluid were generally similar in their sperm-immobilizing activity, viscoelasticity index, electrophoretic patterns, and binding characteristics to Concanavalin A; thus, the sperm-immobilizing factor obtained by gel filtration chromatography and the immobilin fraction obtained by centrifugation are believed to be the same products. Further, it was shown that intraluminal testicular fluids did not inhibit cauda sperm motility even at epididymal-like protein concentrations; thus, it is believed that the sperm-immobilizing factor(s) is of epididymal, not testicular, origin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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