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  • 1
    ISSN: 0006-3592
    Keywords: CHO cells ; serum-free medium ; adaptation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using an adaptive strategy, Chinese hamster ovary (CHO) cell lines were developed that are capable of robust growth in serum-free suspension culture. These preadapted derivatives of the commonly used strain of CHO cells (CHO DUKX), termed PA-DUKX, were used for the introduction and stable expression of several heterologous human genes. A significant advantage of recombinant PA-DUKX cells was their ability to readily resume growth in serum-free suspension culture after transfection and amplification of heterologous genes. Expression of recombinant human proteins in PA-DUKX cells was quantitatively similar to that of lineages generated using conventional CHO DUKX cells. In addition, recombinant human proteins expressed by transfected PA-DUKX lineages were shown to be biochemically and structurally similar to those expressed in CHO DUKX cells, PA-DUKX host cell technology provides an opportunity for reducing the time and resources required to develop large-scale, suspension culture-based manufacturing processes employing serum-free medium. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 11 (1993), S. 79-86 
    ISSN: 0263-6484
    Keywords: Aldehyde dehydrogenase ; alcohol dehydrogenase ; aldehyde reductase ; glutathione-S-transferase ; hepatoma ; 4-hydroxynonenal ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: 4-Hydroxynonenal (4-HNE), produced during the oxidative lipid breakdown of biological membranes, modulates various biochemical processes in normal liver and in hepatoma cells. It is very probable that the effects of 4-HNE are related to the quantity formed in the cells and the cells' ability to metabolize it. Aldehyde catabolism takes place within the cells through oxidative and reductive enzymes, and through conjugation with intracellular glutathione. In this paper, the various enzymatic pathways involved in the metabolism of 4-HNE were studied in normal hepatocytes and in hepatoma cells. The hepatocyte pathway undergoes a complex variety of change during neoplastic transformation.In hepatoma cells, generally, 4-HNE metabolism was due mainly to aldehyde dehydrogenases, whereas in normal hepatocytes 4-HNE metabolism was mainly due to alcohol dehydrogenase and glutathione-S-transferase. The increase in oxidative enzymes compared to normal tissue was not the same in all types of hepatoma: in HTC hepatoma cells, the enzyme levels were considerably higher; in AH-130 hepatoma cells of Yoshida, they were lower in subcellular particles and similar in the cytosol. Indeed, consumption of externally-added 4-HNE in hepatoma cells was proportional to their content of 4-HNE metabolizing enzymes.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 380-386 
    ISSN: 0006-3592
    Keywords: reverse micelles ; cutinase ; deactivation ; conformational changes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Deactivation data and fluorescence intensity changes were used to probe functional and structural stability of cutinase in reverse micelles. A fast deactivation of cutinase in anionic (AOT) reverse micelles occurs due to a reversible denaturation process. The deactivation and denaturation of cutinase is slower in small cationic (CTAB/1-hexanol) reverse micelles and does not occur when the size of the cationic reverse micellar water-pool is larger than cutinase. In both systems, activity loss and denaturation are coupled processes showing the same trend with time. Denaturation is probably caused by the interaction between the enzyme and the surfactant interface of the reversed micelle. When the size of the empty reversed micelle water-pool is smaller than cutinase (at W0 5, with W0 being the water:surfactant concentration ratio) a three-state model describes denaturation and deactivation with an intermediate conformational state existing on the path from native to denaturated cutinase. This intermediate was clearly detected by an increase in activity and shows only minor conformational changes relative to the native state. At W0 20, the size of the empty water-pool was larger than cutinase and the data was well described by a two-state model for both anionic and cationic reverse micelles. For AOT reverse micelles at W0 20, the intermediate state became a transient state and the deactivation and denaturation were described by a two-state model in which only native and denaturated cutinase were present. For CTAB/1-hexanol reverse micelles at W0 20, the native cutinase was in equilibrium with an intermediate state, which did not suffer denaturation. 1-Hexanol showed a stabilizing effect on cutinase in reverse micelles, contributing to the higher stabilities observed in the cationic CTAB/1-hexanol reverse micelles. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:380-386, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0006-3592
    Keywords: enzymatic peptide synthesis ; N-terminal protecting groups ; α-chymotrypsin ; experimental design ; partition constant ; reaction rate ; log P ; molecular refractivity ; response surfaces ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the α-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH2 was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-α protection choice. Boc and Z were the most reactive N-α groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 22-27 
    ISSN: 0006-3592
    Keywords: cDNA copy number ; gene dosage ; recombinant protein production ; posttranslational modification ; BHK ; secretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The secretion rate of activated protein C (APC) by BHK cells was increased 35-fold by increasing the cDNA copy number per cell from 50 to 240. In this range, the relation between APC secretion and cDNA copy number was not linear and the rate of APC secretion per cDNA copy increased sevenfold. This apparent cooperative effect of multiple cDNA copies could be related to their integration in tandem. For cDNA copy numbers higher than 240, the APC secreation rate per cDNA and per cell decreased dramatically. The γ-carboxylation of glutamic acid residues, a posttranslational modification required for APC biological activity, was also investigated. The proportion of APC that was fully γ-carboxylated decreased as the secretion rate of APC increased. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion is described of phenolsulphonephtalein (phenol red) to 3,3′,5,5′-tetrabromophenolsulphonephthalein (bromophenol blue) by bromoper-oxidase from the brown alga Ascophyllum nodosum. This reaction provides a convenient assay for the detection of bromoperoxidase activity in vitro. Bromoperoxidase was shown to be stable under turnover conditions for three weeks at room temperature, catalyzing the bromination of phenol red into bromophenol blue. When stored at room temperature in organic sol vents such as acetone, methanol, ethanol [present up to 60% (v/v)], and 1-propanol [40% (v/v)], bromoperoxidase was stable for more than one month. As far as we know this is the first example of an oxidoreductase which displays such great stability. This enhances the applicability of the enzyme in organic synthesis.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 727-732 
    ISSN: 0006-3592
    Keywords: lipase kinetics ; Candida cylindracea ; hydrolysis of triacetin ; hollow-fiber membrane reactor ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aptitude of a hollow-fiber membrane reactor to determine lipase kinetics was investigated using the hydrolysis of triacetin catalyzed by lipase from Canadida cylindracea as a model system. The binding of the lipase to the membrane appears not to be very specific (surface adsorption), and probably its conformation is hardly altered by immobilization, resulting in an activity comparable to that of the enzyme in its native form. The reaction kinetics defined on the membrane surface area were found to obey Michaelis-Menten kinetics. The specific activity of the lipase in the membrane reactor was found to be significantly higher than in an emulsion reactor. The activity and stability of the enzyme immobilized on a hydrophilic membrane surface seem not to be influenced significantly by the choice of the membrane material. The hollow-fiber membrane reactor is a suitable tool to assess lipase kinetics in a fast and convenient way.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 194-201 
    ISSN: 0006-3592
    Keywords: denitrification kinetics ; nitrite inhibition model ; Pseudomonas fluorescens ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using a pure culture of Pseudomonas fluorescens as a model system nitrite inhibition of denitrification was studies. A mineral media with acetate and nitrate as sole electron donor and acceptor, respectively, was used. Results obtained in continuous stirred-tank reactors (CSTR) operated at pH values between 6.6 and 7.8 showed that growth inhibition depended only on the nitrite undissociated fraction concentration (nitrous acid). A mathematical model to describe this dependence is put forward. The maximum nitrous acid concentration compatible with cell growth and denitrification activity was found to be 66 μg N/L. Denitrification activity was partially associated with growth, as described by the Luedeking-Piret equation. However, when the freshly inoculated reactor was operated discontinuosly, nitrite accumulation caused growth uncoupling from denitrification activity. The authors suggest that these results can be interpreted considering that (a) nitrous acid acts as a proton uncoupler; and (b) cultures continuoulsy exposed to nitrous acid prevent the uncoupling effect but not the growth inhibition. Examination of the growth dependence on nitrite concentration at pH 7.0 showed that adapted cultures (grown on CSTR) are less sensitive to nitrous acid inhibition than the ones cultivated in batch. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 552-556 
    ISSN: 0006-3592
    Keywords: stirring ; turbulence ; shear effects ; lysine fermentation ; Brevibacterium flavum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Excess turbulence caused by high-intensity stirring inhibited microbial growth and metabolism. In stirred tank bioreactors, the growth rate and lysine biosynthesis decreased in Brevibacterium flavum beyond 900 rpm, the growth rate of Trichoderma reesei on wheat straw beyond 150 rpm, and the growth rate of Saccharomyces cerevisae beyond 800 rpm. The term turbohypobiosis was introduced to describe this inhibition. Turbohypobiosis was characterized by a stress factor Fstr expressing the interaction of medium flow with microbial cells in local turbulent zones, dependent on the energy distribution of the stirring regime. Lysine synthesis was inhibited at significantly lower Fstr values than the growth of B. flavum. The main reason for the inhibition was shear effects causing decreased adenosine triphosphate (ATP) generation, lower O2 uptake, and lower specific growth rate of bacteria.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 16-24 
    ISSN: 0006-3592
    Keywords: Michaelis-Menten kinetics ; biocatalyst particles ; oxygen microsensor ; intrinsic kinetics ; modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the application of immobilized enzymes, the influence of immobilization on the activity of the enzyme should be Known. This influence can be obtained by determining the intrinsic kinetic parameters of the immobilized enzyme, and by comparing them with the kinetic parameters of the suspended enzyme. This article deals with the determination of the intrinsic kinetic parameters of an agarose-gel bead immobilized oxygen-consuming enzyme: L-lactate 2-monooxygenase. The reaction rate of the enzyme can be described by Michaelis-Menten kinetics. Batch conversion experiments using a biological oxygen monitor, as well as steady-state profile measurements within the biocatalyst particles using an oxygen microsensor, were performed. Two different mathematical methods were used for the batch conversion experiments, both assuming a pseudosteady-state situation with respect to the shape of the profile inside the bead. One of the methods used an approximate relation for the effectiveness factor for Michaelis-Menten kinetics which interpolates between the analytical solutions for zero- and first-order kinetics. The other mathematical method was based on a numerical solution and combined a mass balance over the reactor with a mass balance over the bead. The main difference in the application of the two methods is the computer calculation time; the completely numerical calculation procedure was about 20 times slower than the other calculation procedure.The intrinsic kinetic parameters resulting from both experimental methods were compared to check the reliability of the methods. There was no significant difference in the intrinsic kinetic parameters obtained from the two experimental methods. By comparison of the kinetic parameters for the suspended enzyme with the intrinsic kinetic parameters for the immobilized enzyme, it appeared that immobilization caused a decrease in the value of Vm by a factor of 2, but there was no significant difference in the values obtained for Km.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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