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1

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Immobilization of glucose oxidase in thin polypyrrole films: Influence of polymerization conditions and film thickness on the activity and stability of the immobilized enzyme (1993)

Almeida, Nicholas F. ; Beckman, Eric J. ; Ataai, Mohammad M.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 42 (1993), S. 1037-1045

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ISSN: 0006-3592

Keywords: enzyme immobilization ; glucose oxidase ; polypyrrole films ; electrodeposition ; biosensors ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Using monomers that polymerize to form electrically conducting polymers, one can control the thickness of the polymer film and the amount of enzyme that can be immobilized in the films. First, an investigation of the major variables that influence the immobilization of glucose oxidase by entrapment in polypyrrole films, prepared by electropolymerization from aqueous solutions containing the enzyme and monomer, was carried out. Then the optimized conditions were used to assess the effects of film thickness on the activity and stability of immobilized enzyme. For the films ranged in thickness from 0.1 μm to 1.6 μm, the resulting apparent activity and stability of the immobilized enzyme were found to be a strong function of the polymer film thickness. Above a thickness of 1.0 μm, the apparent activity of the immobilized enzyme increases linearly with increasing film thickness. The nonlinearity observed for films of thickness less than 1.0 μm can be attributed to the changes observed in the morphology of the resulting polypyrrole films. Furthermore, it was noted that when the glucose oxidase/polypyrrole films are stored in phosphate buffer, at 4°C, the observed rate of loss in apparent activity of the immobilized enzyme is highest for the first few days, also being higher for the thinner films. However, after the loosely entrapped enzyme is leached from the polymer film, the rate of loss in activity is very low indicating that the well-entrapped enzyme, as well as the polypyrrole films, exhibit good stability. Finally, the reproducibility of the immobilization technique is excellent. © 1993 John Wiley & Sons, Inc.

Additional Material: 13 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260420904

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2

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Sustained and constitutive high levels of protein production in continuous cultures of bacillus subtilis (1995)

Vierheller, Chenzhao ; Goel, Akshay ; Peterson, Michael ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 47 (1995), S. 520-524

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ISSN: 0006-3592

Keywords: bacillus subtilis ; plasmid ; continuous culture ; CAT ; recombinant cultures ; acid formation ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: The feasibility of continuous production of proteins in chemostat cultures of Bacillus subtilis was investigated. An expression system consisting of the bacterium B. subtilis BR151 carrying plasmid p602/19 was used. The plasmid contains the cat (chioramphenicol acetyltrans-ferase) gene downstream of a strong vegetative T5 promoter. It was found that, at a dilution rate of 0.2 h-1 production of relatively high levels of CAT protein (about 4% ofcellular protein) can be sustained. But, experiments at a higher dilution rate of 0.4 h-1 were unproductive because of high acidformation and washout. Combination of low cell yield, which results from excessive acid formation, and low dilution rate led to a low volumetric CAT productivity. Our recent work with the nonrecombinant cells, has demonstrated that uptake of small amounts of citrate significantly reduces or entirelyeliminates the acid formation. This superior performance in the presence ofcitrate was hypothesized, based on strong experimental evidence, to be the result of a reduction in glycolysis flux through a sequence of events leading to a reduction in pyruvate kinase and phosphof- ructokinase activities, the regulatory enzymes of glycol-ysis. In this study, it is demonstrated that cofeeding of glucose and citrate substantially reduces theorganic acid formation and significantly increases the recombinant culture productivity. The combination of high specific CAT activity and cell density resulted in a total of six- to tenfold higher culture productivitywhen citrate and glucose were cometabolized than when glucose was the only carbon source. © 1995 John Wiley & Sons Inc.

Additional Material: 4 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260470503

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3

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IMA chromatography of a cell extract: Effect of loading pH on protein purification (1997)

Patwardhan, Anshuman V. ; Ataai, Mohammad M.

Hoboken, NJ : Wiley-Blackwell

AIChE Journal 43 (1997), S. 3232-3240

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ISSN: 0001-1541

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Immobilized metal ion affinity chromatography has shown promise for isolating desired proteins from host cell extracts, based on differential affinities for chelated metal ions. This article focuses on modeling the effect of loading pH on the purity and binding capacity of target proteins, during their separation from the cell extract of Escherichia coli, using immobilized copper affinity chromatography. Early chromatography experiments revealed that cellular proteins of E. coli elute in two separate peaks from an immobilized copper column under a decreasing pH step gradient. Thus, the cell extract is modeled by a mixture of two proteins, tuna heart cytochrome c and chicken egg white lysozyme. Transport and binding parameters of these proteins are evaluated over a wide pH range and used in a mathematical model of multicomponent chromatography. Target proteins are chosen such that they elute at a pH between the elution pH of cytochrome and lysozyme. Simulation results showed that decreasing the loading pH to a value between the elution pH of the weaker copper binding proteins of E. coli and that of the target protein may not only decrease the amount of E. coli proteins bound in the column but lead to a substantially higher binding capacity for the target protein.

Additional Material: 11 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/aic.690431211

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4

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Utilization of glucose and amino acids in insect cell cultures: Quantifying the metabolic flows within the primary pathways and medium development (1993)

Ferrance, Jerome P. ; Goel, Akshay ; Ataai, Mohammad M.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 42 (1993), S. 697-707

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ISSN: 0006-3592

Keywords: Spodoptera frugiperda ; glycolysis ; TCA cycle ; amino acids ; efficient growth medium ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: The current understanding of insect cell metabolism is very limited. In order to gain some insight into the growth and metabolism of insect cells Spodoptera frugiperda (Sf9), a comprehensive characterization of culture conditions for cells grown in the IPL-41 medium was made by measuring the amino acid composition of the growth medium and the cell extract, the macromolecular composition of the cells (DNA, RNA, and protein), medium concentrations of various metabolites and sugars, and the evolved CO2. Since in the IPL-41-based serum-free medium all of the amino acids except cysteine are in great excess of what is needed by the cells for energy and protein production, a medium formulation with an osmolarity similar to the IPL-41 but with a lower amino acid content than IPL-41 was also developed. The new medium also lacks maltose and sucrose (contains only glucose), supported cell growth to a high cell density of 8 × 106 cells/mL. The cellular and energetic yields indicated that a tight coupling between the biosynthetic and energetic reactions was attained for cells grown in the new medium. Moreover, it was found that the intermittent feeding of glucose may not be required as the cell yield and growth rate were comparable whether the same total amount of glucose was provided intermittently or was included initially in the medium. The eventual cessation of growth in the new medium is believed to be due to the amino acid limitation because concentrations of both glutamine and glutamate were very low at the end of the growth phase. Thus, further optimization, which may include higher initial glutamine in the medium or its intermittent feeding, could lead to a further increase in the cell density. Finally, a stoichiometrically based analysis of metabolic reactions confirmed the operation of the key pathways and was used to quantify the distribution of metabolites among primary metabolic reactions. The quantitative flow values were used to highlight some key aspects of insect cell metabolism. © 1993 John Wiley & Sons, Inc.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bit.260420604

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5

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β-relaxation of drawn isotactic polypropylene in terms of a simplified two phase model (1994)

Jawad, S. A. ; Alhaj-Mohammad, M. H.

New York, NY [u.a.] : Wiley-Blackwell

Polymer International 35 (1994), S. 395-398

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ISSN: 0959-8103

Keywords: Isotactic polypropylene ; drawing ; β-relaxation ; compliance ; loss factor ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: β-Relaxation in die-drawn isotactic polypropylene (i-pp) is associated with a glass transition temperature and depends on the mobility of the molecules in the amorphous regions. A simplified two phase model was employed to explain the decrease in the intensity of the β-process peak upon drawing. The model predicts that the decrease in the loss factor (tan δ) upon drawing is associated with a change in continuity from a series to a parallel situation.

Additional Material: 6 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pi.1994.210350413

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6

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Reactions of Acetylenic Esters with Cyclic Ketones and Substituted Acetophenones (1979)

Shandala, Mowafak Y. ; Al-Khashab, Abdel-Elah Y. ; Al-Jobour, Nazar H. ; [et al.]

New York, NY : Wiley-Blackwell

Journal für Praktische Chemie/Chemiker-Zeitung 321 (1979), S. 899-904

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ISSN: 0021-8383

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Reaktionen von Acetylenestern mit cyclischen Ketonen und substituierten AcetophenonenDie Kondensation von substituierten Phenylpropiolsäureestern mit cyclischen Ketonen führt zu polycyclischen Pyronen. Die Kombination spektroskopischer Methoden zeigt, daß Cyclopentanon zu 4-Pyronen (I), Cyclohexanon, Cycloheptanon, Cyclooctanon dagegen zu 2-Pyronen (IIa-f) reagiert.Die Kondensation von Ethylarylpropiolaten mit p-Piperazino, p-Piperidino, p(4-Methylpiperazino) und p-Morpholinoacetophenonen ergibt die p-(4-Arylpropiolylpiperazino) acetophenone (IIIa-d), 2-(p-Piperidinophenyl)-6-aryl-4-pyrone (IVa-c), 2-(p-4-Methylpiperazino-phenyl)-6-aryl-4-pyrone (Va-c) und 2-(p-Morpholinophenyl)-6-aryl-4-pyrone (VIa - d). Die Acetylen-β-diketone (VII) erhält man aus Ethyl-p-tolylpropiolat mit p-Piperidinoacetophenon.

Additional Material: 2 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/prac.19793210603

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7

Electronic Resource

Raman spectra of alkali halide/NCO- systems (1983)

Mohammad, M. R. ; Sherman, W. F.

Chichester [u.a.] : Wiley-Blackwell

Journal of Raman Spectroscopy 14 (1983), S. 215-218

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ISSN: 0377-0486

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The Raman spectra of twelve different alkali halide/NCO- systems have been investigated, and these spectra have been compared with the previously-studied infrared spectra. In the external mode region there are significant differences in the infrared and Raman spectra associated with the in-band features.

Additional Material: 4 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jrs.1250140317

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