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  • 1
    Electronic Resource
    Electronic Resource
    Mathematical model for the luminol chemiluminescence reaction catalyzed by peroxidase (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1112-1120 
    Details
    ISSN: 0006-3592
    Keywords: luminol chemiluminescence ; peroxidase ; hydrogen peroxide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model that accurately describes intensity vs. time reaction profiles for the chemiluminescence reaction between luminol and hydrogen peroxide, as catalyzed by horseradish perioxdase, is derived and evaluated. A set of three differential equations is derived and solved to provide intensity time information for the first 200 seconds of the reaction. The model accurately predicts intensity-time profiles when literature values are used for all but one of the reaction rate constants. Furthermore, the model predicts a nonlinear curve for plots of light intensity versus the initial hydrogen peroxide concentration. Experimental data confirm that such plots are nonlinear. Finally, a linear double-reciprocal plot is predicted by the model and the experimental data verify this relationship. © 1993 Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260411115
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  • 2
    Electronic Resource
    Electronic Resource
    Organic solvents strip water off enzymes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 392-397 
    Details
    ISSN: 0006-3592
    Keywords: T2O desorption ; water stripping ; organic solvents ; enzymes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exchange of enzyme-bound H2O with T2O in aqueous solution followed by freeze drying provided tritiated water bound to chymotrypsin, subtilisin Carlsberg, and horseradish peroxidase. The desorption of T2O from these enzymes suspended in various organic solvents showed that all three enzymes lost enzyme-bound water with peroxidase losing the most T2O of the three in solvents of moderate to high polarity. Polar solvent resulted in the highest degree of T2O desorption (e.g., methanol desorbed from 56%-62% of the bound T2O), while nonpolar solvents resulted in the lowest degree of desorption (e.g., hexane desorbed from 0.4%-2% of the bound T2O). Desorption is nearly immediate with most of the desorbable T2O being released from the enzymes within the first 5 min. Both solvent dielectric and a measure of the saturated molar solubility of water in a given solvent provide accurate correlations between the properties of the organic solvents and the extent of T2O desorption. This investigation shows that water stripping from an enzyme into a nonaqueous medium does occur and can be significant in polar solvents.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390405
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  • 3
    Electronic Resource
    Electronic Resource
    Controlling enzyme-catalyzed regioselectivity in sugar ester synthesis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 426-434 
    Details
    ISSN: 0006-3592
    Keywords: regioselectivity of enyzmatic catalysis ; sucrose acylation in organic solvents ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rational control over enzyme-catalyzed regioselectivity has been studied using sucrose acylation by vinyl esters in organic media as a model. Subtilisins BPN' and Carlsberg preferentially acylate at the 1′-hydroxyl of sucrose with some acylation observed at the 6-hydroxyl. The preference for the 1′-hydroxyl is strongly affected by the hydrophobicity of the organic solvent and the chain length of the vinyl ester. Increasingly hydrophobic solvents and longer chain lengths lower the favorable formation of the 1′-acylation and improve 6-acylation. Molecular modeling of sucrose in the binding pocket of subtilisin BPN' shows that the 1′-acylation is favored in solvents that can solvate sugars (such as pyridine) as the glucose moiety is exposed to the medium, whereas 6-acylation leaves the entire sucrose molecule buried within the enzyme's binding pocket. Thus, 1′-acylation is sterically more favorable than 6-acylation. Increasingly hydrophobic solvents affect regioselectivity by changing the degree of solvation of the glucose moiety in the medium and forcing the sucrose 1′-ester completely into the binding pocket. In a related modeling, the vinyl ester chain length was shown to modulate regioselectivity by controlling the bond angles between the resulting acylenzymes and the sucrose thereby affecting the positioning of the sucrose in the binding pocket of subtilisin BPN'. This study shows that control over enzymic regioselectivity can be achieved by rational choices of substrate and solvent. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450507
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  • 4
    Electronic Resource
    Electronic Resource
    Enzymatic synthesis of a sucrose-containing linear polyester in nearly anhydrous organic media (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 639-646 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic synthesis ; anhydrous pyridine ; trifluoroethylbutyrate ; transesterification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A variety of enzymes have been found to acylate sucrose in anhydrous pyridine. The enzymic reaction is highly selective; with trifluoroethylbutyrate as ester donor, enzyme-catalyzed transesterification of sucrose yielded sucrose 1′-butyrate and sucrose 6, 1′-dibutyrate. No sucrose-tributyrates were formed. Using a similar technique, a long-chain linear sucrose polyester has been prepared using Proleather, an alkaline protease from a Bacillus sp. This protease catalyzes the esterification of sucrose with bis(2, 2, 2-trifluoroethyladipate) in a 1:1 ratio to yield a sucrose-containing polyester with Mw = 2100 and Mn = 1600 for a polydispersity of 1. 31. Polymers with molecular weights in excess of 13, 000 have been prepared by this enzymic approach, indicating that molecules containing over 30 sucrose units have been produced. The polyester is extremely water soluble and soluble in polar organic solvents. As with the sucrose dibutyrate, the polyester has ester linkages at the C6 and C1′ positions on the sucrose. The polyester can be depolymerized using Proleather in aqueous buffer, pH7. After 9 days in aqueous buffer, Proleather catalyzed the breakdown of the polyester to an Mw of ca. 900. This sucrose-containing polyester may have applications as a water-absorbent, biodegradable plastic for use as diapers and hygienic products, water-treatment chemicals, and components of drug delivery systems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370706
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  • 5
    Electronic Resource
    Electronic Resource
    Biocatalytic synthesis of disaccharide high-intensity sweeterner sucralose via a tetrachlororaffinose intermediate (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 211-217 
    Details
    ISSN: 0006-3592
    Keywords: chemical chlorination ; enzymic hydrolysis ; mycelial pellets ; raffinose ; sucralose tetrachlororaffinose ; M. vinacea ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A second high-yielding bioorganic synthesis of the highintensity sweetener sucralose (4,1′,6′-trichloro-4,1′,6′-trideoxygalactosucrose) is described. This procedure involves the chemical chlorination of raffinose to form a novel tetrachloroaffinose intermediate (6,4′,1″,6″-tetrachloro-6,4′,1″,6″-tetradeoxygalactoraffinose; TCR) followed by the enzymic hydrolysis of the α-1-6 glycosidic bond of TCR to give sucralose and 6-chlorogalactose. Commercial enzyme preparations and microorganisms were screened to select α-galactosidases which have high catalytic activity on this compound. The most active enzyme was produced by a strain of Mortierella vinacea and had a maximum rate of 118 μmol sucralose/g dry weight cells/h, which was approximately 5% of the activity toward raffinose, and a Km of 5.8 mM toward TCR. The enzyme could be used in the form of mycelial pellets in a continuous packed bed column reactor. The reaction was also studied in a water-immiscible hydrophilic organic solvent, such as methyl isobutyl ketone, to overcome the poor aqueous solubility of TCR and to increase volumetric productivity. Synthesis of raffinose was achieved from saturated aqueous solutions of galactose and sucrose using a selected α-galactosidase from Aspergillus niger. When raffinose is used as a starting material for sucralose synthesis, this route has fewer steps than either the preceeding method using glucose-6-acetate as an intermediate or the complete chemical synthesis from sucrose. The relative merits of the two bioorganic routes and the utility of such methods to synthesize new sugars are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390213
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure affects enzyme function in organic media (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 772-776 
    Details
    ISSN: 0006-3592
    Keywords: enzymes, pressure on ; catalysis ; enzyme hydration ; organic solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pressure affects enzyme function in nonaqueous media. Activation volumes have been determined and provide evidence that the primary effect of pressure is to enhance the stripping of water off an enzyme in polar organic solvents and leads to decreased enzymatic activity. Activation volumes of subtilisin Carlsberg in organic solvents, particularly with the enzyme hydrated, have a larger magnitude than activation volumes determined in aqueous solutions. This study provides further evidence that enzymatic activity in polar organic solvents is dominated by the interaction of enzyme-bound water with the solvent. From a practical standpoint, however, the results of this study suggest that enzymatic catalysis in organic solvents may be controlled by the combined effects of pressure and enzyme hydration. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420613
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical and Monte Carlo simulations of phenolic polymerizations catalyzed by peroxidase (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 807-814 
    Details
    ISSN: 0006-3592
    Keywords: peroxidase-catalyzed polymerizations ; numerical modeling ; Monte-Carlo simulations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Numerical and Monte Carlo simulations of horseradish peroxidase-catalyzed phenolic polymerizations have been performed. Kinetic constants for the simulations were fit to data from the oxidation and polymerization of bisphenol A. Simulations of peroxidase-catalyzed phenolic polymerization were run as a function of enzyme concentration and radical transfer and radical coupling rate constants. Predictions were performed with respect to conversion vs. time and number average molecular weight and polydispersity vs. conversion. It is shown that the enzymatic polymerization of phenols can be optimized with respect to high molecular weights by employing low enzyme concentrations and phenols with low radical coupling rate constants coupled with relatively high radical transfer rate constants. Such phenols may be identified by using linear free energy relationships that relate radical reactivity to electron donating/withdrawing potential of the phenolic substituent. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420704
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  • 8
    Electronic Resource
    Electronic Resource
    Transition state stabilization of subtilisins in organic media (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 515-520 
    Details
    ISSN: 0006-3592
    Keywords: subtilisin ; organic solvents ; transition state stabilization ; EPR spectroscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Electrostatic forces are among the stabilizing interactions that contribute to the high degree of enzyme-transition state complementarity. The active-site polarity, which can differ substaintially from that of water, is thus an important determinant of transition state stabilization. Here we pose the question of whether the rate of an enzymatic reaction proceeding through a charged transition state can be increased by increasing the active-site polarity in an organic solvent. The active-site polarity of subtilisin has been reduced by dehydration and suspension in a nonpolar solvent (tetrahydrofuran), and then increased by adding water to the solvent. Enhancing the local polarity substantially increasing the rate of catalysis, implicating polarity as an important factor in stabilizing the charged tetrahedral transition state. Studies with subtilisins whose active sites have been modified by site-directed mutagenesis support the role of polarity in transition state stabilization. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430612
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  • 9
    Electronic Resource
    Electronic Resource
    Enzymatic analyses in organic solvents (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 28 (1986), S. 417-421 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Horseradish peroxidase has been found to vigorously act as a catalyst in a number of water-immiscible organic solvents. The rates of peroxidase-catalyzed oxidation of p-anisidine with H2O2 in toluene, benzene, ethyl and butyl acetates, and ether are in the range of 10-25% of that in water (pH 7.0) at the same reactant concentrations. Per oxidase was coupled with cholesterol oxidase (which was also found to be catalytically active in organic media), and the bienzymic system was successfully used for accurate, reliable, and reproducible determination of cholesterol in toluene.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260280315
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  • 10
    Electronic Resource
    Electronic Resource
    Polymerization of phenols catalyzed by peroxidase in nonaqueous media (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 30 (1987), S. 31-36 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polymers produced by horseradish-peroxidase-catalyzed coupling of phenols have been explored as potential substitutes for phenol-formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous-organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water-miscible solvents such as dioxane, acetone, di-methylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 × 104 D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase-catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(p-phenylphenol) and poly(p-cresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p-phenylphenol) was found to have a much higher electrical conductivity than phenol-formaldehyde resins.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260300106
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