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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 51 (1979), S. 96-100 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 56 (1984), S. 591-593 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 326 (1979), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1436-5073
    Keywords: photopolymerisation ; poly(vinyl alcohol) ; coating ; amperometric ; biosensor ; choline oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biosensors are based on the intimate association of a transducer and of a sensing layer. The latter can be a preformed membrane further connected to the transducer, or a thin film directly deposited on its surface. As the stability is a key parameter to be considered, a polymer with high potentialities for this purpose was chosen to form a direct surface coating: a poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ). Choline oxidase was entrapped in this photo-cross-linkable gel for making an enzyme electrode through controllable steps. The influence of the ratio PVA-SbQ/enzyme was studied and the stability of the resulting modified electrodes was determined. After deposition of minute volumes (10–45 μl) including no more than one unit of choline oxidase and 0.3 mg of polymer, an efficient choline sensor was obtained. It exhibited a fast response time lower than 30 s, a low detection limit of 2.5 nM choline, a wide linear range extending up toca. 10–4 M and good stability, both operational and on storage. This method appears promising for making miniaturized biosensors.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sorbitol dehydrogenase was bound to the surface of acyl-azide-activated collagen membranes and its kinetics was investigated as a model of two-substrate or cofactor-requiring enzyme reactions. The study was performed with the “rotating membrane reactor” especially designed to obtain a precise variation of the external mass-transfer coefficient, and thus the direct visualization of diffusional effects on the bound enzyme behavior. Diffusional limitations for NADH were found to decrease the apparent affinity for NADH, but to increase the apparent affinity for fructose. Such opposite effects of diffusional limitations on apparent affinities are generally applicable to reactions involving two substrates or a substrate and a cofactor of widely different affinities.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 1055-1068 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Films of highly polymerized collagen, prepared in industrial conditions, were chosen for surface covalent binding of enzymes because of their insolubility, mechanical resistance, proteic nature, hydrophilic properties and for their abundance in chemically activable —COOH. Untanned films, previously acid- methylated, were activated by acyl azide formation. After removal of reagents by repeated washing, the coupling of enzyme was performed by immersion of the activated film in the enzyme solutions (2 to 3 hr, 0°C). The procedure is particularly mild since the enzymes never come into contact with chemical reagents, and thus avoid all denaturing processes. All the enzymes tested were successfully bound: glutamate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, aspartate aminotransferase, glutamate pyruvate transaminase, creatine kinase, hexokinase, trypsin, and urease. As tested with aspartate amino transferase, enzymatic activity remained constant for months (100% after 5 months) in spite of repeated use of the film at 30°C, washing and storage in buffer at 4°C between assays.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 125-142 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Amyloglucosidase was covalently bound to collagen sheets by a previously described method. The time of acidic methylation (first step of the collagen activation process) was important to obtain a good enzymatic surfacic activity. Homogeneity of the coupling procedure on the surface of collagen films was shown. Some properties of free enzyme were not affected after grafting: optimum pH and temperature, activation energy, and Km for maltose. Heat stability of the bound enzyme was slightly better; Km for soluble starch increased fivefold. In contrast, the maximal velocity in the presence of soluble starch remained four times that of maltose hydrolysis.Amyloglucosidase collagen membranes were used in a helicoidal reactor to produce glucose from maltose or soluble starch solutions. Tracer studies have shown that the helicoidal reactor behaved as a CSTR. The influence of maltose concentration and flow rate on conversion was studied and confirmed the absence of diffusional limitations for maltose. Recycling of concentrated solutions of maltose and soluble starch indicated strong diffusional restrictions for soluble starch. The catalytic support kept all its activity for 18 days continuous operation at 40°C and 80% after 17 months storage at 4°C.
    Additional Material: 16 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 665-669 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Single- and double-stranded DNA were immobilized on films of highly polymerized collagen by a covalent process. The coupling was efficient at an acidic pH with an optimum at pH 5, while preventing the collagen film from any damage. In addition, no leakage occurred, so it was possible to use this DNA-coated collagen film as an immunoadsorbent. Therefore the findings reported here suggest that the acyl-azide procedure is also suitable for DNA binding on a proteinic support. Promising results in specific clearance of DNA antibodies were obtained in vitro.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 232-237 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Firefly luciferase from Photinus pyralis has been covalently bound to a collagen strip via an acylazide activation process. Immobilization performed in the presence of both substrates ATP and luciferin allows to increase the activity retained on the strip. The best activity exhibited by immobilized luciferase was obtained in a 0.05M Tris-acetate buffer, pH 7.75. The pH optimum and the activation energy of luciferase have been found unchanged after immobilization. In the chosen stirring conditions, no diffusional limitations of substrates appear. ATP measurements can be performed with collagen-bound luciferase in the range 1.10-11 M-3.10-6 M. It was possible to store the strips at 4°C in a dehydrated form; then, the bound enzyme retains 20% of its initial activity after eight months. Human blood ATP was measured with this collagen-bound luciferase and the results were found in good agreement with those obtained by soluble luciferase.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 1154-1158 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetic properties of collagen-bound firefly luciferase have been investigated. Under definite hydrodynamic conditions with low agitation in the reaction medium, the observed behavior is modified compared to the enzyme free in solution: reducing the stirring rate decreases the observed enzymatic activity. But diffusional resistances alone cannot account for these atypical kinetics though mass transfer may certainly play an important role during the transient state of the bioluminescent reaction. After immobilization, the time necessary to reach the steady state increased from 300 ms to 3 min and the two substrates, luciferin and ATP, behave differently with respect to the enzyme: The nature of the saturating substrate first in contact with the bound enzyme is not indifferent suggesting that immobilization can reveal behaviors or mechanisms which are not visualized with the free enzyme.
    Additional Material: 4 Ill.
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