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  • 11
    Electronic Resource
    Electronic Resource
    Two-Step biocatalytic conversion of an ester to an aldehyde in reverse micelles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 232-241 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; alcohol dehydrogenase ; reverse micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipases from Candida cyclindracea (L-1754) and wheat germ (L-3001) have been used to hydrolyze esters to their corresponding alcohols and acids in reverse micelles. Alcohol dehydrogenase from baker's yeast (YADH) was subsequently used to reduce the alcohol products to aldehydes. Cofactor recycling in the redox reaction was achieved using a sacrificial cosubstrate, as described previously. Four surfactants (sodium dioctylsulfosuccinate, Nonidet P-40 with Triton X-35, polyoxyethylene, 10-cetyl-ether, polyoxyethylene sorbitan trioleate) were employed to determine the effect of amphiphile on ester hydrolysis and redox reaction rates separately. The effect of type of organic solvent, W0 [(water]/[surfactant)], and substrate concentration on separte enzyme activity were also investigated. A brief investigation of a single phase, two-step reaction catalyzed by the combination of lipase and YADH in reverse micelles is also reported. The activities of the enzymes are significantly different when used together instead of independently. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430307
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  • 12
    Electronic Resource
    Electronic Resource
    High pressure EPR studies of protein mobility in reversed micelles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 342-348 
    Details
    ISSN: 0006-3592
    Keywords: organic solvents ; reversed micelles ; protein mobility ; EPR spectra of enzymes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have investigated the effect of pressure on structural properties of subtilisin solubilized in reversed micelles of Tween-85/isopropanol in hexane. Electron paramagnetic resonance (EPR) spectra of spin-labeled enzyme indicate a reduction in spin-label mobility when the enzyme is transferred from aqueous solution to the microemulsion. One explanation for the spectral broadening is a change in the protein's active-site conformation and/or dynamics. However, over a W0 range of 80 to 180, EPR spectroscopy could detect no change in the enzyme's environment, conformation, or molecular dynamics. The EPR spectra also contained a contribution from free spin label located in an environment with a polarity roughly between that of propanol and bulk water. No changes in the polarity surrounding the free spin label nor in the enzyme's structural properties were evident at pressures up to 10,000 psi. Previous work has demonstrated that pressure can be used to manipulate the size of some reversed micelles, and the EPR data indicated that for this system such pressure tuning of micellar properties will not adversely affect the structure of solubilized enzyme. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430412
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  • 13
    Electronic Resource
    Electronic Resource
    Synthesis of protein-containing polymers in organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 10-17 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; enzymes ; immobilization ; biopolymers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Subtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free-radical initiated polymerization. The activity and stability of the PEG-modified enzymes have been determined in aqueous buffer and organic solvents. The Km and Vmax values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half-lives of both modified enzymes were remarkably high (up to 2 months). The protein-containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450103
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  • 14
    Electronic Resource
    Electronic Resource
    A comparison of lipase-catalyzed ester hydrolysis in reverse micelles, organic solvents, and biphasic systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 60-70 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; lipase ; reverse micelles ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of lipases from Candida rugosa and wheat germ have been investigated in three reaction media using three acetate hydrolyses as model reactions (ethyl acetate, allyl acetate, and prenyl acetate). The effect of substrate properties and water content were studied for each system (organic solvent, biphasic system, and reverse micelles). Not unexpectedly, the effect of water content is distinct for each system, and the optimal water content for enzyme activity is not always the same as that for productivity. A theoretical model has been used to simulate and predict enzyme performance in reverse micelles, and a proposed partitioning model for biphasic systems agrees well with experimental results. While the highest activities observed were in the micellar system, productivity in microemulsions is limited by low enzyme concentrations. Biphasic systems, however, support relatively good activity and productivity. The addition of water to dry organic solvents, combined with the dispersion of lyophilized enzyme powders in the solvent, resulted in significant enzyme aggregation, which not surprisingly limits the applicability of the “anhydrous” enzyme suspension approach. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470108
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  • 15
    Electronic Resource
    Electronic Resource
    Protein purification by bulk crystallization: The recovery of ovalbumin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 316-323 
    Details
    ISSN: 0006-3592
    Keywords: ovalbumin ; bulk crystallization ; crystalgrowth rate ; nucleation ; purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Crystallization is used industrially for the recovery and purification of many inorganic and organic materials. However, very little is reported on the application of bulk crystallization for proteins. In this work, ovalbumin was selected as a model protein to investigate the feasibility of using bulk crystallization for the recovery and purification of proteins. A stirred 1-L seeded batch crystallizer was used to obtain the crystal growth kinetics of ovalbumin in ammonium sulfate solutions at 30°C. The width of the metastable region, in which crystal growth can occur without any nucleation, is equivalent to a relative supersaturation of about 20. The bulk crystallizations were undertaken within this range (using initial relative supersaturations less than 10) and nucleation was not observed. The ovalbumin concentration in solution was measured by UV absorbance and checked by crystal content measurement. Crystal size distributions were measured both by using a Malvern Mastersizer and by counting crystals through a microscope. The crystal growth rate was found to have a second-order dependence upon the ovalbumin supersaturation. While there is no discernible effect of ammonium sulfate concentration at pH 4.90, there is a slight effect at higher pH values. Overall the effect of ammonium sulfate concentration is small compared to the effect of pH, for which there is a 10-fold increase in the growth rate constant, kGσ over the range pH 4.6-5.4. To demonstrate the degree of purification which can be achieved by bulk crystallization, ovalbumin was crystallized from a solution containing conalbumin (80,000 Da) and lysozyme (14, 600 Da). After one crystallization and a crystal wash, ovalbumin crystals were produced with a protein purity greater than 99%. No contamination by the other proteins was observed when using overloaded sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) stained with Coomassie blue stain and only trace amounts of lysozyme were observed using a silver stain. The presence of these other proteins in solution did not effect the crystal growth rate constant, kGσ. The study demonstrates the feasibility of using bulk crystallization for the recovery and purification of ovalbumin. It should be readily applicable to other protein systems. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480404
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  • 16
    Electronic Resource
    Electronic Resource
    The role of hydration in enzyme activity and stability: 1. Water adsorption by alcohol dehydrogenase in a continuous gas phase reactor (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 700-708 
    Details
    ISSN: 0006-3592
    Keywords: alcohol dehydrogenase ; enzyme ; water sorption isoterm ; gas phase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The adsorption of water by alcohol dehydrogenase from baker's yeast (YADH) has been measured in a continuous-flow gas reactor at varying temperatures. Adsorption isotherms in the presence of gaseous organic substrates are compared to those from organic-free gas mixtures. Almost no effect of the hydrophobic molecule on total water adsorption was observed. A rarely mentioned multilayer isotherm model from the 1930s, the Huttig's isotherm, has been found to fit the experimental data with extremely good accuracy. The model enables the calculation of both the heat of adsorption of water to the enzyme and the total amount of water necessary for monolayer coverage. The heat of adsorption of water in the first layer is approximately -16 kcal/mol. This tight binding of water, which is much higher than the heat of condensation of pure water, helps to explain the kinetic properties of YADH-catalyzed reactions on vapor phase substrates. While the monolayer coverage is temperature independent, the enzyme demonstrates hysteresis when transitioning between adsorption and desorption. The hysteresis observed in water sorption studies may also explain previously reported properties of the enzyme. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    The role of hydration in enzyme activity and stability: 2. Alcohol dehydrogenase activity and stability in a continuous gas phase reactor (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 709-716 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; gas phase ; alcohol dehydrogenase ; hydration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The degree of enzyme hydration is the one of the most important factors which can affect enzyme activity and stability in water-limited environments. Alcohol dehydrogenase from baker's yeast (YADH) has been used as a model enzyme to study the effects of hydration on activity, stability, and cofactor stability with gas phase substrates. In all cases, the enzyme is essentially inactive until a temperature-independent degree of surface coverage by water molecules has been reached. The critical water content corresponds to 40-50% of a single monolayer. Careful control of the degree of hydration, by adjustments to gas humidity and temperature, enables the enzyme to be stabilized for periods exceeding 1 month, whereas in water the half-life of the enzyme is 30 min. The reaction with gas phase substrates follows a pseudo-first-order mechanism with an activation energy of 7.5 ± kcal/mol, which is almost half of that in aqueous solution. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Covalent binding of a nerve agent hydrolyzing enzyme within polyurethane foams (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 450-457 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; immobilization ; phosphotriesterase ; polyurethane foam ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A phosphotriesterase preparation, extracted from Escherichia coli DH5α cells, was immobilized within a polyurethane foam matrix during polymer synthesis. The enzyme-foam interaction was shown to be covalent and analysis of the hydrolysis of paraoxon in aqueous solution demonstrated that more than 50% of the initial enzyme specific activity was retained after immobilization in the foam. Factors affecting the rate of paraoxon degradation include foam hydrophobicity, the degree of mixing applied to initiate polymerization, and foam pretreatment prior to use in substrate hydrolysis. The storage stability of the foam is significant, with phosphotriesterase-foam activity profiles exhibiting a three month half-life. Foams are currently being developed for biocatalytic air filtering, in which gaseous substrates will be simultaneously adsorbed and degraded by the immobilized enzyme system. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Dramatically stabilized phosphotriesterase - polymers for nerve agent degradation (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 105-114 
    Details
    ISSN: 0006-3592
    Keywords: enzymes ; phosphotriesterase ; immobilization ; polyurethane foam ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phosphotriesterase (EC 3.1.8.1) was immobilized within a polyurethane foam matrix during polymer synthesis using a prepolymer synthesis strategy. In addition to retaining greater than 50% of the enzyme specific activity, numerous benefits were incurred upon immobilization. Orders of magnitude increases in storage and thermal stability (net stabilization energy = 12.5 kJ/mol) were observed without the need for enzyme premodification. The immobilized enzyme system was protease resistant and seemed to display no adverse effects from immobilization, such as an alteration of enzyme function. The organic solvent, dimethyl sulfoxide, also exhibited a stabilizing effect on phosphotriesterase enzyme systems over a range of intermediate concentrations. We attribute these effects in part to direct interaction between the aprotic solvent and metal containing residues present at the enzyme's active site. Our data demonstrate that just 2.5 kg of immobilized enzyme may be sufficient to degrade 30,000 tons of nerve agent in just 1 year. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 105-114, 1997.
    Additional Material: 11 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Transfer vectors for maximal expression of passenger genes in the Bombyx mori nuclear polyhedrosis virus expression system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1293-1300 
    Details
    ISSN: 0006-3592
    Keywords: baculoviruses ; transfer vectors ; expression vectors ; chloramphenicol acetyl transferase ; metallothionein ; deletion mutagenesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A series of Bombyx mori nuclear polyhedrosis virus (Bm-NPV) transfer vectors has been developed containing various lengths of the polyhedrin promoter, including sequences 3′ of the initiation codon. The ATG initiation codon was mutated in some of these vectors to allow for the production of authentic nonfusion proteins. The ability of the various polyhedrin promoter constructs to direct expression of foreign gene sequences was assessed using two test genes, chloramphenicol acetyl transferase (cat), and human metallothionein II. Accumulation of cat mRNA and nonfused protein was low when only polyhedrin promoter sequences to -8 (relative to the translational start site of polyhedrin mRNA) were included in the transfer vector, but cat expression was comparable with that of the wild-type polyhedrin gene when promoter sequences to +5 were present. Further addition of polyhedrin gene sequences to +26 or +94 resulted in no further increase in expression. Similar results were obtained for expression of human metallothionein II, where constructs encoding polyhedrin-metallothionein fusion proteins containing polyhedrin sequences to at least +5 resulted in high levels of mRNA and protein accumulation. The expression vectors containing the +5, +26, or +94 BmNPV polyhedrin promoter can thus be used to direct maximal levels of production of nonfused proteins (when the polyedrin ATG has been mutated) or of fusion proteins, depending on which is more suitable for a particular application. These new vectors are a useful addition to those presently available and should increase the utility of the BmNPV expression system for large-scale protein production. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260421106
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