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  • Biochemistry and Biotechnology  (69)
  • Analytical Chemistry and Spectroscopy
  • EARTH RESOURCES AND REMOTE SENSING
  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1995-1999  (78)
  • 1980-1984
  • 1997  (78)
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  • 1995-1999  (78)
  • 1980-1984
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  • 1
    ISSN: 1075-4261
    Schlagwort(e): cholelithiasis ; gallstone ; bile salts ; periodic precipitation ; fractal precipitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: This is the first observation that both chaotic and periodic patterns are formed in metal ions-deoxycholate-gel systems. It is an in vitro model for approximating the conditions present during gallstone formation. The experimental results suggest that a nonlinear scientific concept such as the “butterfly effect” should be considered in understanding gallstone formation. This effect suggests that a butterfly flapping its wings in Beijing today may lead to a thunderstorm in New York months later. Applying this concept to biology, minor changes in the local chemical environment within biological systems may lead to large variations in the structure and morphology of gallstone through changes in the behavior of biological mineralization process. © 1997 John Wiley & Sons, Inc. Biospect 3: 195-205, 1997
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 372-378 
    ISSN: 0006-3592
    Schlagwort(e): glucose ; lactate ; on-line monitoring ; mammalian cell culture ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: On-line monitoring and control of cell culture fermentation is important for optimal and consistent production of biologicals. In this work, glucose and lactate concentrations are monitored on-line using a commercially available analyzer (Model 2700, Yellow Springs Instruments, Yellow Springs, OH) during batch and perfusion hybridoma cell fermentation. Cell free samples from the reactor are obtained using a 0.45 μm hollow fiber filtering system placed in a circulation loop. The samples were analyzed at specified times and the data are collected on a computer. A process control strategy was developed to control the concentrations of glucose and lactate in a perfusion reactor where the feed rate is adjusted to maintain their concentrations at desired set points. Hybridoma cells (A10G10) were cultivated in a high density perfusion culture where cell density increased from 2 to 14 million cells/mL. During this period the control algorithm successfully adjusted the perfusion rate while maintaining constant glucose and lactate concentrations. Glucose consumption and lactate accumulation rates as well as net lactate yield on glucose were monitored continuously during perfusion culture. These metabolic rates were observed to be independent of cell concentration and were used for the estimation of viable cell density in the reactor. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 372-378, 1997.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0006-3592
    Schlagwort(e): methanol sensor ; methanol monitoring and control ; methylotrophic yeast fermentation ; Pichia pastoris ; transferrin ; shake-flask cultures ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The methylotrophic yeast Pichia pastoris can be used to express recombinant genes at high levels under the control of the methanol-inducible alcohol oxidase 1 (AOX1) promoter. Accurate regulation of the methanol concentration in P. pastoris cultures is necessary to maintain induction, while preventing accumulation of methanol to cytotoxic levels. We developed an inexpensive methanol sensor that uses a gas-permeable silicone rubber tube immersed in the culture medium and an organic solvent vapor detector. The sensor was used to monitor methanol concentration continuously throughout a fed-batch shake-flask culture of a P. pastoris clone producing the N-lobe of human transferrin. The sensor calibration was stable for the duration of the culture and the output signal accurately reflected the methanol concentration determined off-line by HPLC. A closed-loop control system utilizing this sensor was developed and used to maintain a 0.3% (v/v) methanol concentration in the culture. Use of this system resulted in a fivefold increase in volumetric protein productivity over levels obtained using the conventional fed-batch protocol. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 279-286, 1997.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 153-164 
    ISSN: 0006-3592
    Schlagwort(e): hybridoma ; oxygen ; serum-free medium ; continuous culture ; antioxidant ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The murine B-lymphocyte hybridoma, CC9C10 was grown at steady state under serum-free conditions in continuous culture at dissolved oxygen (DO) concentrations in the range of 10% to 150% of air saturation. Cells could be maintained with this range at high viability in a steady state at a dilution rate of 1 d-1, although with lower cell concentrations at higher DO. A higher specific antibody production measured at higher DO was matched by a decrease in the viable cell concentration at steady state, so that the volumetric antibody titre was not changed significantly. An attempt to grow cells at 250% of air saturation was unsuccessful but the cells recovered to normal growth once the DO was decreased.There was a requirement for cellular adaptation at each step-wise increase in dissolved oxygen. Adaptation to a DO of 100% was associated with an increase in the specific activities of glutathione peroxidase (×18), glutathione S-transferase (×11) and superoxide dismutase (×6) which are all known antioxidant enzymes. At DO above 100%, the activities of GPX and GST decreased possibly as a result of inactivation by reactive oxygen radicals.The increase in dissolved oxygen concentration caused changes in energy metabolism. The specific rate of glucose uptake increased at higher dissolved oxygen concentrations with a higher proportion of glucose metabolized anaerobically. Short-term radioactive assays showed that the relative flux of glucose through glycolysis and the pentose phosphate pathway increased whereas the flux through the tricarboxylic acid cycle decreased at high DO. Although the specific glutamine utilization rate increased at higher DO, there was no evidence for a change in the pattern of metabolism. This indicates a possible blockage of glycolytic metabolites into the TCA cycle, and is compatible with a previous suggestion that pyruvate dehydrogenase is inhibited by high oxygen concentrations.Analysis of the oxygen uptake rate of cell suspensions at steady state under all conditions showed a pronounced Crabtree effect which was manifest by a decrease (up to 40%) in oxygen consumption on addition of glucose. This indicates that the degree of aerobic metabolism in these cultures is highly sensitive to the glucose concentration. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 153-164, 1997.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 1075-4261
    Schlagwort(e): black pigment gallstone ; FTIR ; EPR ; nonlinear phenomena ; vibrational mode ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Further spectroscopic studies of gallstones are reviewed with an emphasis on the formation of black pigment gallstones. This type of gallstone appears mainly in Western countries, with only 3% of the cholelithiasis patients in China having black gallstones. Fourier transform infrared absorption and electron paramagnetic resonance are used as spectroscopic probes of gallstones and their metal bilirubinate components. Nonlinear phenomena in gallstone formation were investigated through the appearance of ring structure in gallstones and fractal patterns in the formation in the precipitates of bile salt systems. Although a complete understanding of gallstone formation has not yet been achieved, interesting progress toward this goal has been made recently. © 1997 John Wiley & Sons, Inc. Biospectroscopy 3: 381-391, 1997
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 0173-0835
    Schlagwort(e): Nonaqueous capillary electrophoresis ; Dynamic complexation ; Porphyrin ; Additives ; Separation theory ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The effect of an additive (Brij 35) on the mobilities of a group of porphyrin acids is quantitatively characterized based on a 1:1 dynamic complexation model. Varying additive concentration shifts the equilibrium and changes the viscosity of the background electrolyte. The equilibrium constant, the electrophoretic mobility of the free analyte, and the electrophoretic mobility of the complex are identified as the parameters necessary to describe the analytes' migration behavior. Several statistical methods for obtaining these parameters are discussed. The equilibrium constants and complex mobilities are calculated using three different linear regression methods. The weighted y-reciprocal method was preferred because it gives smaller error, and the data points are evenly distributed along the concentration axis. These values are confirmed using a nonlinear regression to ensure that the proper weighting was used in the linear regression plots. The parameters are then used to predict the apparent mobilities of the analytes over the entire additive concentration range, allowing the optimum separation conditions to be identified. For disclike molecules, such as porphyrins, the mobility is determined by the orientation of the molecule in an electric field, in addition to their size and charge. The strength of binding between the porphyrins and Brij 35 depends on the number of binding sites and the solvation shell.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 0173-0835
    Schlagwort(e): Capillary electrophoresis ; Lipoproteins ; Apoproteins ; Ultracentrifuge ; Mass spectrometry ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: A new program for lipoprotein characterization is outlined where capillary electrophoresis (CE) plays a central role in the analysis of intact lipoprotein serum components and the apoprotein domains. The first characterization step involves separation and particle density analysis of very low-, low-, and high-density lipoprotein fractions (VLDL, LDL, HDL) by ultracentrifugation and image analysis. VLDL, HDL, and LDL fractions are analyzed by capillary electrophoresis. Sodium dodecyl sulfate (SDS) at low concentrations in the background electrolyte used in the CE analysis is incorporated into the lipoprotein particle without appreciable delipidation, as determined by ultracentrifuge particle density analysis. Increasing the concentration of SDS results in extensive delipidation, resulting in the release of apoproteins (apo) which are detected as components of the electropherogram. Apo B-100 is detected in the delipidated VLDL and LDL fractions along with micelles of the lipids. Micelles from LDL delipidation have uniform charge densities. Apo A-I and A-II are detected in the HDL fraction. A new method for lipoprotein delipidation is introduced where the lipoprotein fraction is adsorbed on a reversed-phase hydrophobic cartridge. Delipidation and recovery of the apoprotein fractions is made by serial clutions with acetonitrile. CE of the lipid-free apoprotein mixture shows the presence of apoC-I,II,III and apoE in the VLDL fraction, and apoA-I,II apoC-I and apoE in the HDL fraction. Electrospray ionization mass spectrometry analysis gives the isoform distribution for each apoprotein. The identification of the apoproteins in the electropherograms is the first step in developing a CE-based quantitation method for measuring serum levels of these apoproteins and their distribution between the lipoprotein fractions. The assay described in this paper is being used as a level 2 and 3 cardiac risk profile analysis for individuals with normal lipid profiles who have a documented or family history of cardiovascular disease.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 0173-0835
    Schlagwort(e): Two-dimensional polyacrylamide gel electrophoresis ; Tears ; Proteome ; Cancer ; Tag Sequencing ; Amino acid analysis ; Lacryglobin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: To understand the changes in protein expression associated with various physiological states as well as the development of pathological eye disease, we have begun to map the protein components of normal human reflex tears. An analytical reference map of normal human reflex tears was created using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) with pH 3.5-10 immobilized pH gradients (IPGs). Micropreparatively loaded gels were transferred to polyvinylidene difluoride (PVDF) and analysed by a combination of N-terminal sequence tagging and amino acid compositional analysis. Thirty spots were sequence tagged, resulting in identification of six different proteins (lipocalin, lysozyme, lactotransferrin, zinc-α-2 glycoprotein, cystatin S, cystatin SN) that matched to entries in the SWISS-PROT database. A group of N-terminally blocked proteins was clearly identified from SWISS-PROT by amino acid analysis, isoelectric point (pI) and molecular weight (Mr). A number of highly expressed protein components remain unidentified despite being subjected to amino acid analysis and Edman sequencing. A majority of the abundant proteins showed varying degrees of charge heterogeneity attributed to post-translational processing such as glycosylation and N-terminal truncation. We have identified a previously undescribed protein that we have named lacryglobin. This protein displays strong homology with mammaglobin, a protein overexpressed in breast cancer. The discovery of this homologue in tears offers the potential for disease diagnosis by screening tear fluid proteins.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Electrophoresis 18 (1997), S. 1086-1091 
    ISSN: 0173-0835
    Schlagwort(e): Immobilized pH gradients ; Two-dimensional polyacrylamide gel electrophoresis ; Tumor necrosis factor α ; Glycosylated isoform ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: The mouse macrophage cell-line RAW264.7, stimulated with lipopolysaccharide, was used as a model for the study of the production of tumor necrosis factor (TNF) isoforms. TNF is synthesised initially as a 26 kDa transmembrane precursor, which is then processed enzymatically by a protease to release a mature molecule of 17 kDa. Dose-dependent production of transmembrane TNF was assessed by fractionation of cell membranes and Western blot analysis followed by autoradiography and densitometry. Isoforms of both the precursor and mature molecules were separated using two-dimensional (2-D) electrophoresis with immobilised pH gradient 3-10 linear gels as the first dimension. After radiolabelling of cells with 35S, both cell-associated and supernate-associated TNF isoforms were immunoprecipitated. A large number of protein spots were visualised on the 2-D gel map, for both the transmembrane and mature TNF species, more than have been detected previously using one-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The likelihood that these putative isoforms were the result of differential glycosylation was tested by preincubating the cells with tunicamycin. This had the effect of reducing the number of protein spots, notably the higher molecular weight species. There were a number of precursor TNF isoforms that were unchanged upon tunicamycin treatment and these presumably reflect protein modifications other than glycosylation.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 547-555 
    ISSN: 0006-3592
    Schlagwort(e): ethanol ; cellulose ; hemicellulose ; endoglucanase ; cellulase ; lignocellulose ; biomass ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This study demonstrates a new approach to reduce the amount of fungal cellulase required for the conversion of cellulose into ethanol. Escherichia coli KO11, a biocatalyst developed for the fermentation of hemicellulose syrups, was used to produce recombinant endoglucanase as a co-product with ethanol. Seven different bacterial genes were expressed from plasmids in KO11. All produced cell-associated endoglucanase activity. KO11(pLOI1620) containing Erwinia chrysanthemi celZ (EGZ) produced the highest activity, 3,200 IU endoglucanase/L fermentation broth (assayed at pH 5.2 and 35°C). Recombinant EGZ was solubilized from harvested cells by treatment with dilute sodium dodecyl sulfate (12.5 mg/ml, 10 min, 50°C) and tested in fermentation experiments with commercial fungal cellulase (5 filter paper units/g cellulose) and purified cellulose (100 g/L). Using Klebsiella oxytoca P2 as the biocatalyst, fermentations supplemented with EGZ as a detergent-lysate of KO11(pLOI1620) produced 14%-24% more ethanol than control fermentations supplemented with a detergent-lysate of KO11(pUC18). These results demonstrate that recombinant bacterial endoglucanase can function with fungal cellulase to increase ethanol yield during the simultaneous saccharification and fermentation of cellulose. © 1997 Wiley & Sons, Inc. Biotechnol Bioeng 55: 547-555, 1997.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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