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  • 1
    Electronic Resource
    Electronic Resource
    Electrostatic and Electrokinetic Interactions during Protein Transport through Narrow Pore Membranes (1994)
    s.l. : American Chemical Society
    Industrial & engineering chemistry research 33 (1994), S. 2473-2482 
    Details
    ISSN: 1520-5045
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ie00034a032
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  • 2
    Electronic Resource
    Electronic Resource
    Membrane handbook edited by W. S. Winston Ho, and Kamalesh K. Sirkar, Van Nostrand Reinhold, New York, 1992, 954 pp. $131.95 (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2343-2344 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411024
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusive and convective protein transport through asymmetric membranes (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1497-1510 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data are obtained for bovine serum albumin transport through asymmetric polyethersulfone ultrafiltration membranes of differing molecular weight cutoff in a stirred ultrafiltration device. The actual membrane sieving coefficient is determined from filtrate concentration measurements using a stagnant film model to account for bulk mass transport effects. These sieving coefficients are then used to evaluate the relative contributions of diffusive and convective transport to the overall protein flux. The results are in good agreement with available hydrodynamic models for the hindrance factors for convective and diffusive transport of spherical solutes through well-defined pores, with the effective solute to pore size ratio evaluated from a partitioning model that explicitly accounts for the ellipsoidal shape of the protein and the membrane pore size distribution. The implications of these results to the analysis of experimental data for membrane sieving and to the design of effective protein fractionation devices are also discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690371007
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of intermolecular thiol-disulfide interchange reactions on bsa fouling during microfiltration (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 972-982 
    Details
    ISSN: 0006-3592
    Keywords: membrane fouling ; microfiltration ; protein aggregation ; sulfhydryl reactions ; protein separation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several studies have shown that one of the critical factors governing protein fouling of microfiltration membranes is the presence of denaturedand/or aggregated protein in the bulk solutions. Experiments were performed to evaluate the role of intermolecular disulfide interchange reactionson protein aggregation and membrane fouling during stirred cell microfiltration of bovine serum albumin (BSA). The flux decline during BSA filtration was quite dramatic due to the formation of a protein deposit thatfully covered the membrane pores. This flux decline could be completely eliminated by capping the free sulfhydryl group present on the BSA with eithera carboxymethyl or cysteinyl group, demonstrating the critical importance of this free thiol in the intermolecular aggregation reactions and, in turn, protein fouling. BSA aggregation during storage could be reduced by the addition of metal chelators (EDTA and citrate) or dithiothreitol, orby storage at lower pH (7.0) these solutions all had a significantly lower rate of fouling upon subsequent filtration. This behavior is completely consistent with the known chemistry of the thiol-disulfide interchange reaction, demonstrating that an understanding of these intermolecular (aggregation) reactions can provide a rational framework for the analysis and control of protein fouling in these membrane systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440814
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  • 5
    Electronic Resource
    Electronic Resource
    Protein fouling during microfiltration: Comparative behavior of different model proteins (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 91-100 
    Details
    ISSN: 0006-3592
    Keywords: microfiltration ; membrane ; protein ; fouling ; filtration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent studies of protein fouling have provided considerable insight into both the underlying fouling mechanisms and the mathematical description of the flux decline. However, most of the data have been obtained with a single model protein, making it difficult to generalize the results to commercially relevant process streams. Experiments were thus performed using a range of proteins with different physicochemical characteristics to determine the relationship between the protein structure and fouling behavior. Fouling in these systems occurred by two distinct mechanisms: deposition of large protein aggregates and chemical attachment of native proteins to the growing deposit. The chemical attachment generally occurred via the formation of intermolecular disulfide linkages involving a free sulfhydryl group in the native protein. Proteins without a free sulfhydryl group were typically unable to form these intermolecular linkages. The quasi-steady flux for the different proteins was proportional to the square of the protein surface charge density, consistent with a model in which protein deposition occurs when the drag force on the proteins associated with the convective filtrate flow is sufficient to overcome electrostatic repulsive interactions. These results clearly demonstrate the importance of the protein structure, charge, and reactivity in determining the rate and extent of protein fouling during microfiltration. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 91-100, 1997.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Protein fractionation using electrostatic interactions in membranel filtration (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 406-414 
    Details
    ISSN: 0006-3592
    Keywords: membrane filtration ; protein separations ; albumin ; hemoglobin ; electrostatic interactions ; diafiltration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the critical factors limiting the development of membrane systems for protein fractionation has been the poor selectivity that has generally been obtained with these membrane devices. We have demonstrated that it is possible to dramatically improve the selectivity of available membrane systems by exploiting the different electrostatic interactions between the two proteins and the membrane. The separation factor for the albumin-hemoglobin system could be increased to more than 70 simply by reducing the salt concentration and adjusting the pH to around 7 (near the isoelectric point of hemoglobin). This very high selectivity was a direct result of the strong electrostatic exclusion of the charged albumin from the membrane pores under these conditions. This high selectivity makes it possible to very effectively separate these albumin-hemoglobin mixtures using membrane filtration, and this was demonstrated experimentally using both a simple batch filtration process and a continuous diafiltration system. The hemoglobin recovery in the diafiltration experiment was greater than 70% after a 3-diavolume filtration, with the Hb purification factor being around 100 under these conditions. These results clearly demonstrate the potential of membrane systems for the fractionation of proteins even with very similar molecular weights. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480413
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of protein fouling during ultrafiltration using a two-layer membrane model (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 451-460 
    Details
    ISSN: 0006-3592
    Keywords: protein fouling ; membrane transport ; ultrafiltration ; adsorption ; filtration ; composite membrane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Protein fouling can significantly alter both the flux and retention characteristics of ultrafiltration membranes. There has, however, been considerable controversy over the nature of this fouling layer. In this study, hydraulic permeability and dextran sieving data were obtained both before and after albumin adsorption and/or filtration using polyethersulfone ultrafiltration membranes. The dextran molecular weight distributions were analyzed by gel permeation chromatography to evaluate the sieving characteristics over a broad range of solute size. Protein fouling caused a significant reduction in the dextran sieving coefficients, with very different effects seen for the diffusive and convective contributions to dextran transport. The changes in dextran sieving coefficients and diffusive permeabilities were analyzed using a two-layer membrane model in which a distinct protein layer is assumed to form on the upstream surface of the membrane. The data suggest that the protein layer formed during filtration was more tightly packed than that formed by simple static adsorption. Hydrodynamic calculations indicated that the pore size of the protein layer remained relatively constant throughout the adsorption or filtration, but the thickness of this layer increased with increasing exposure time. These results provide important insights into the nature of protein fouling during ultrafiltration and its effects on membrane transport. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:451-460, 1998.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of solution environment on the permeability of red blood cells (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 115-121 
    Details
    ISSN: 0006-3592
    Keywords: cell transport ; creatinine ; membrane transport ; permeability ; red blood cells ; uric acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cell membrane permeability governs the rate of solute transport into and out of the cell, significantly affecting the cell's metabolic processes, viability, and potential usefulness in both biotechnological applications and physiological systems. Most previous studies of the cell membrane permeability have neglected the possible effects of suspending medium on membrane transport, even though there is extensive experimental evidence that suspending phase composition can significantly affect other properties related to the cell membrane (e.g., cell deformability, fragility, and aggregation rate). This study examined the effects of suspending phase composition (both proteins and electrolytes) on the permeability of human red blood cells to the metabolites creatinine and uric acid. Data were obtained using a stirred ultrafiltration device with direct cell- and proteinfree sampling through a semipermeable membrane. Both the uric acid and creatinine permeabilities were strongly affected by the suspending phase composition, with the permeabilities in different buffer solutions varying by as much as a factor of three. The predominant factors affecting the permeability were the presence (or absence) of chloride, phosphate/adenine, and proteins, although the magnitude and even the direction of these effects were significantly different for creatinine and uric acid transport. The dramatic differences in behavior for uric acid and creatinine reflect the different transport mechanisms for these solutes, with uric acid transported by a carrier-mediated mechanism and creatinine transported by passive diffusion through the lipid bilayer. These results provide important insights into the effects of solution environment on cell membrane transport and other cell membrane-mediated properties. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430203
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of solution pH and ionic strength on the separation of albumin from immunoglobulins (IgG) by selective filtration (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 960-968 
    Details
    ISSN: 0006-3592
    Keywords: membrane filtration ; protein separation ; albumin ; immunoglobulins ; electrostatic interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although protein fractionation by selective membrane filtration has numerous potential applications in both the downstream processing of fermentation broths and the purification of plasma proteins, the selectivity for proteins with only moderately different molecular weights has generally been quite poor. We have obtained experimental data for the transport of bovine serum albumin (BSA) and immunoglobulins (IgG) through 100,000 and 300,000 molecular weight cutoff polyethersulfone membranes in a stirred ultrafiltration device at different solution pH and ionic strength. The selectivity was a complex function of the flux due to the simultaneous convective and diffusive solute transport through the membrane and the bulk mass transfer limitations in the stirred cell. Under phsioligical conditions (pH 7.0 and 0.15 M NaCI) the maximum selectivity for the BSA-IgG separation was only about 2.0 due primarily to the effects of protein adsorption. In contrast, BSA-IgG selectivities as high as 50 were obtained with the same membranes when the protein solution was at pH 4.8 and 0.0015 M NaCl. This enhanced selectivity was a direct result of the electrosatatic contributions to both bulk and membrane transport. The membrane selectivity could actually be reversed, with higher passage of the larger IgG molecules, by using a 300,000 molecular weight cutoff membrane at pH 7.4 and an ionic strength of 0.0015 M NaCl. These results clearly demonstrate that the effectiveness of selective protein filtration can be dramatically altered by appropriately controlling electrostatic interactions through changes in pH and/or ionic strength. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431009
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  • 10
    Electronic Resource
    Electronic Resource
    High performance tangential flow filtration (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 71-82 
    Details
    ISSN: 0006-3592
    Keywords: tangential flow filtration ; ultrafiltration ; size exclusion chromatography ; protein purification ; fractionation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional tangential flow filtration (TFF) has traditionally been limited to separation of solutes that differ by about ten-fold in size. Wide pore-size distributions, membrane fouling, and concentration polarization phenomena have commonly been cited as reasons for this limitation. The use of TFF in the biotechnology industry has therefore been restricted to cell-protein, virus-protein, and protein-buffer separations. A multi-disciplinary team with industrial and academic members was formed to overcome these limitations and enable protein-protein separations using High Performance TFF (HPTFF) systems. Pore-size distributions have been improved with the development of new membrane formulation and casting techniques. Membrane fouling has been controlled by operating in the transmembrane pressure-dependent regime of the filtrate flux curve and by carefully controlling fluid dynamic start-up conditions. Concentration polarization was exploited to enhance, rather than limit, the resolution of solutes. Concentration polarization has also been controlled by operating a co-current filtrate stream that maintains transmembrane pressure constant along the length of the TFF module. High yields and purification factors were obtained even with small differences in protein sieving. IgG-BSA and BSA monomer-oligomer mixtures have successfully been separated with these systems. HPTFF technology provides a competitive purification tool to complement chromatographic processing of proteins. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 71-82, 1997.
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