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  • 1
    Electronic Resource
    Electronic Resource
    Protein denaturation by combined effect of shear and air-liquid interface (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 503-512 
    Details
    ISSN: 0006-3592
    Keywords: aggregation by air-liquid interface ; foaming ; rhDNase ; rhGH ; shear ; shear rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of shear alone on the aggregation of recombinant human growth hormone (rhGH) and recombinant human deoxyribonuclease (rhDNase) has been found to be insignificant. This study focused on the synergetic effect of shear and gas-liquid interface on these two model proteins. Two shearing systems, the concentric-cylinder shear device (CCSD) and the rotor/stator homogenizer, were used to generate high shear (〉 106) in aqueous solutions in the presence of air. High shear in the presence of an air-liquid interface had no major effect on rhDNase but caused rhGH to form noncovalent aggregates. rhGH aggregation was induced by the air-liquid interface and was found to increase with increasing protein concentration and the air-liquid interfacial area. The aggregation was irreversible and exhibited a first-order kinetics with respect to the protein concentration and air-liquid interfacial area. Shear and shear rate enhanced the interaction because of its continuous generation of new air-liquid interfaces. In the presence of a surfactant, aggregation could be delayed or prevented depending upon the type and the concentration of the surfactant. The effect of air-liquid interface on proteins at low shear was examined using a nitrogen bubbling method. We found that foaming is very detrimental to rhGH even though the shear involved is low. The use of anti-foaming materials could prevent rhGH aggregation during bubbling. The superior stability exhibited by rhDNase may be linked to the higher surface tension and lower foaming tendency of its aqueous solution. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 503-512, 1997.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Effect of high shear on proteins (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 458-465 
    Details
    ISSN: 0006-3592
    Keywords: concentric-cylinder shear device ; rotor/stator homogenization ; shear ; shear rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Shear is present in almost all bioprocesses and high shear is associated with processes involving agitation and emulsification. The purpose of this study is to investigate the effect of high shear and high shear rate on proteins. Two concentric cylinder-based shear systems were used. One was a closed concentric-cylinder shear device (CCSD) and the other was a homogenizer with a rotor/stator assembly. Mathematical modeling of these systems allowed calculation of the shear rate and shear. The CCSD generated low shear rates (a few hundred s-1), whereas the homogenizer could generate very high shear rates (〉 105 s-1). High shear could be achieved in both systems by increasing the processing time. Recombinant human growth hormone (rhGH) and recombinant human deoxyribonuclease (rhDNase) were used as the model proteins in this study. It was found that neither high shear nor high shear rate had a significant effect on protein aggregation. However, a lower melting temperature and enthalpy were detected for highly sheared rhGH by using scanning microcalorimetry, presumably due to some changes in protein's conformation. Also, SDS-PAGE indicated the presence of low molecular-weight fragments, suggesting that peptide bond breakage occurred due to high shear. rhDNase was relatively more stable than rhGH under high shear. No conformational changes and protein fragments were observed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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