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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 700-708 
    ISSN: 0006-3592
    Keywords: α-chymotrypsin ; organic media ; tripeptide synthesis ; CCK-8 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic synthesis of the tripeptide derivative Z-Gly-Trp-Met-OEt is reported. This tripeptide is a fragment of the cholecystokinin C-terminal octapeptide CCK-8. Studies on the α-chymotrypsin catalyzed coupling reaction between Z-Gly-Trp-R1 and Met-R2 have focused on low water content media, using deposited enzyme on inert supports such as Celite and polyamide. The effect of additives (polar organic solvents), the acyl-donor ester structure, the C-α protecting group of the nucleophile, enzyme loading, and substrate concentration were tested. The best reaction medium found was acetonitrile containing buffer (0.5%, v/v) and triethylamine (0.5%, v/v) using the enzyme deposited on Celite as catalyst (8 mg of α-chymotrypsin/g of Celite). A reaction yield of 81% was obtained with Z-Gly-Trp-OCam as acyl donor, at an initial concentration of 80 mM. The tripeptide synthesis was scaled up to the production of 2 g of pure tripeptide with an overall yield of 71%, including reaction and purification steps. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 849-862 
    ISSN: 0887-624X
    Keywords: vinyl acetate ; emulsion polymerization of ; poly(vinyl alcohol) emulsifier ; poly(vinyl alcohol) ; grafting onto ; acetonitrile/water extraction ; water-soluble PVA ; water-insoluble PVA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the emulsion polymerization of vinyl acetate (VAc) using poly(vinyl alcohol) (PVA) as stabilizer and potassium persulfate as initiator, the VAc reacts with PVA forming PVA-graft-PVAc. When the grafted polymer reaches a critical size it becomes water-insoluble and precipitates from the aqueous phase contributing to the formation of polymer particles. Since particle formation and therefore the properties of the final latex will depend on the degree of grafting, it is important to quantify and to characterize the grafted PVA. In this work, the quantitative separation and characterization of the grafted water-insoluble PVA was carried out by a two-step selective solubilization of the PVAc latex, first with acetonitrile to separate PVAc homopolymer, followed by water to separate the water-soluble PVA from the remaining acetonitrile-insoluble material. After the separation, the water-soluble and water-insoluble PVA were characterized by Fourier Transform Infrared (FTIR) spectroscopy and 1H and 13C nuclear magnetic resonance (NMR) analyses, from which the details of the PVA-graft-PVAc structure were obtained. © 1996 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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