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  • 1
    Electronic Resource
    Electronic Resource
    Protein—Protein Interactions in Aqueous Ammonium Sulfate Solutions. Lysozyme and Bovine Serum Albumin (BSA) (2000)
    Springer
    Journal of solution chemistry 29 (2000), S. 699-718 
    Details
    ISSN: 1572-8927
    Keywords: Potential of mean force ; proteins ; salts ; intermolecular interactions ; precipitation ; crystallization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Osmotic pressures have been measured to determine lysozyme—lysozyme,BSA—BSA, and lysosyme—BSA interactions for protein concentrations to 100 g-L−1in an aqueous solution of ammonium sulfate at ambient temperature, as a functionof ionic strength and pH. Osmotic second virial coefficients for lysozyme, forBSA, and for a mixture of BSA and lysozyme were calculated from theosmotic-pressure data for protein concentrations to 40 g-L−1. The osmotic second virialcoefficient of lysozyme is slightly negative and becomes more negative withrising ionic strength and pH. The osmotic second virial coefficient for BSA isslightly positive, increasing with ionic strength and pH. The osmotic second virialcross coefficient of the mixture lies between the coefficients for lysozyme andBSA, indicating that the attractive forces for a lysozyme—BSA pair areintermediate between those for the lysozyme—lysozyme and BSA—BSA pairs. For proteinconcentrations less than 100 g-L−1, experimental osmotic-pressure data comparefavorably with results from an adhesive hard-sphere model, which has previouslybeen shown to fit osmotic compressibilities of lysozyme solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005112927213
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Protein-protein and protein-salt interactions in aqueous protein solutions containing concentrated electrolytes (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 11-21 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; salts ; intermolecular interactions ; potentials of mean force ; precipitation ; crystallization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Protein-protein and protein-salt interactions have been obtained for ovalbumin in solutions of ammonium sulfate and for lysozyme in solutions of ammonium sulfate, sodium chloride, potassium isothiocyanate, and potassium chloride. The two-body interactions between ovalbumin molecules in concentrated ammonium-sulfate solutions can be described by the DLVO potentials plus a potential that accounts for the decrease in free volume available to the protein due to the presence of the salt ions. The interaction between ovalbumin and ammonium sulfate is unfavorable, reflecting the kosmotropic nature of sulfate anions. Lysozyme-lysozyme interactions cannot be described by the above potentials because anion binding to lysozyme alters these interactions. Lysozyme-isothiocyanate complexes are strongly attractive due to electrostatic interactions resulting from bridging by the isothiocyanate ion. Lysozyme-lysozyme interactions in sulfate solutions are more repulsive than expected, possibly resulting from a larger excluded volume of a lysozyme-sulfate bound complex or perhaps, hydration forces between the lysozyme-sulfate complexes. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 11-21, 1998.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
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    Unknown
    Combined Contamination and Space Environmental Effects on Solar Cells and Thermal Control Surfaces (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: For spacecraft in low Earth orbit (LEO), contamination can occur from thruster fuel, sputter contamination products and from products of silicone degradation. This paper describes laboratory testing in which solar cell materials and thermal control surfaces were exposed to simulated spacecraft environmental effects including contamination, atomic oxygen, ultraviolet radiation and thermal cycling. The objective of these experiments was to determine how the interaction of the natural LEO environmental effects with contaminated spacecraft surfaces impacts the performance of these materials. Optical properties of samples were measured and solar cell performance data was obtained. In general, exposure to contamination by thruster fuel resulted in degradation of solar absorptance for fused silica and various thermal control surfaces and degradation of solar cell performance. Fused silica samples which were subsequently exposed to an atomic oxygen/vacuum ultraviolet radiation environment showed reversal of this degradation. These results imply that solar cells and thermal control surfaces which are susceptible to thruster fuel contamination and which also receive atomic oxygen exposure may not undergo significant performance degradation. Materials which were exposed to only vacuum ultraviolet radiation subsequent to contamination showed slight additional degradation in solar absorptance.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106592 , E-8859 , NAS 1.15:106592 , AIAA PAPER 94-2627 , AIAA Aerospace Ground Testing Conference; Jun 20, 1994 - Jun 23, 1994; Colorado Springs, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Atomic Oxygen Durability Evaluation of Protected Polymers Using Thermal Energy Plasma Systems (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The durability evaluation of protected polymers intended for use in low Earth orbit (LEO) has necessitated the use of large-area, high-fluence, atomic oxygen exposure systems. Two thermal energy atomic oxygen exposure systems which are frequently used for such evaluations are radio frequency (RF) plasma ashers and electron cyclotron resonance plasma sources. Plasma source testing practices such as ample preparation, effective fluence prediction, atomic oxygen flux determination, erosion measurement, operational considerations, and erosion yield measurements are presented. Issues which influence the prediction of in-space durability based on ground laboratory thermal energy plasma system testing are also addressed.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106855 , L-9452 , NAS 1.15:106855 , International Conference on Plasma Synthesis and Processing of Materials; Feb 21, 1993 - Feb 25, 1993; Denver, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Low Earth orbital atomic oxygen environmental simulation facility for space materials evaluation (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Simulation of low Earth orbit atomic oxygen for accelerated exposure in ground-based facilities is necessary for the durability evaluation of space power system component materials for Space Station Freedom (SSF) and future missions. A facility developed at the National Aeronautics and Space Administrations's (NASA) Lewis Research Center provides accelerated rates of exposure to a directed or scattered oxygen beam, vacuum ultraviolet (VUV) radiation, and offers in-situ optical characterization. The facility utilizes an electron-cyclotron resonance (ECR) plasma source to generate a low energy oxygen beam. Total hemispherical spectral reflectance of samples can be measured in situ over the wavelength range of 250 to 2500 nm. Deuterium lamps provide VUV radiation intensity levels in the 115 to 200 nm range of three to five equivalent suns. Retarding potential analyses show distributed ion energies below 30 electron volts (eV) for the operating conditions most suited for high flux, low energy testing. Peak ion energies are below the sputter threshold energy (approximately 30 eV) of the protective coatings on polymers that are evaluated in the facility, thus allowing long duration exposure without sputter erosion. Neutral species are expected to be at thermal energies of approximately .04 eV to .1 eV. The maximum effective flux level based on polyimide Kapton mass loss is 4.4 x 10 exp 6 atoms/((sq. cm)*s), thus providing a highly accelerated testing capability.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA-TM-106128 , E-7797 , NAS 1.15:106128 , International SAMPE Symposium and Exhibition; May 10, 1993 - May 13, 1993; Anaheim, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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