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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 50 (1990), S. 319-322 
    ISSN: 1432-0649
    Keywords: 42.65 ; 42.40 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new type of anisotropic scattering with ring-and-line structure is observed for the first time from a BaTiO3 crystal illuminated by a linearly polarized laser beam. The analysis presented herein is based on the photorefractive four-wave interaction of the incident, reflected, and scattered beams. The experimental results agree well with the theoretical analysis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1424
    Keywords: Protein kinase A ; Na+/HCO 3 − cotransporter ; Trypsin digestion ; Regulatory protein ; Protein phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The activity of the Na-H antiporter is inhibited by cyclic AMP-dependent protein kinase A (cAMP.PKA). The inhibitory effect of PKA on the Na-H antiporter is mediated through a regulatory protein that can be dissociated from the antiporter by limited protein digestion. PKA also inhibits the activity of the Na+/ HCO 3 − cotransporter. We investigated whether the activity of Na+/HCO 3 − cotransporter and the effect of PKA on this transporter may also be regulated by limited protein digestion. In rabbit renal cortical basolateral membranes (BLM) and in solubilized BLM reconstituted in liposomes (proteoliposomes), trypsin (100 μg) increased 22Na uptake in the presence of HCO3 but not in the presence of gluconate, indicating that trypsin does not alter diffusive 22Na uptake but directly stimulates the Na+/HCO 3 − cotransporter activity. In proteoliposomes phosphorylated with ATP, the catalytic subunit (CSU) of cAMP-PKA decreased the activity of the Na+/HCO 3 − cotransporter (expressed as nanomoles/mg protein/3s) from 23 ± 10 to 14 ± 6 (P 〈 0.01). In the presence of trypsin, the inhibitory effect of CSU of cAMP-PKA on the activity of Na+/HCO 3 − cotransporter was blunted. To identify a fraction that was responsible for the inhibitory effect of the CSU on the Na+/HCO 3 − cotransporter activity, solubilized proteins were separated by size exclusion chromatography. The effect of CSU of cAMP-PKA on the Na+/HCO 3 − cotransporter activity was assayed in proteoliposomes digested with trypsin with the addition of a fraction containing the 42 kDa protein (fraction S+) or without the 42 kDa protein (fraction S−). With the addition of fraction S−, the CSU of cAMP-PKA failed to inhibit the Na+/HCO 3 − cotransporter activity (control 27 ± 6, CSU 27 ± 3) while the addition of fraction S+ restored the inhibitory effect of CSU (27 ± 6 to 3 ± 0.3 P 〈 0.01). The CSU of cAMP-PKA phosphorylated several proteins in solubilized protein including a 42 kDa protein. Fluorescein isothiocyanate (FITC) labels components of the Na+/HCO 3 − cotransporter including the 56 kDa and 42 kDa proteins. In trypsin-treated solubilized protein the 42 kDa protein was not identified with FITC labeling. The results demonstrate that the activity of the Na+/HCO 3 − cotransporter is regulated by protein(s) which mediates the inhibitory effect of PKA. Limited protein digestion can dissociate this protein from the cotransporter.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1485-1492 
    ISSN: 0887-6266
    Keywords: polymer blend ; phase separation ; transesterification ; interfacial structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Competition between phase separation and transesterification in immiscible polymer blends of polycarbonate (PC) and a copolyester (PET) is studied as a function of time and temperature by differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS). We found that (1) Global structure coarsens at T ≤ 200°C due to the dominance of phase separation over transesterification and melts at T ≤ 220°C due to the dominance of transesterification at the domain interface. However, transesterification is slow but still significant even at T ≤ 200°C. (2) An intricate balance of transesterification and phase separation rates controls global and interfacial structures. (3) Interfacial structures become measurable under certain conditions, and the interfacial thickness between PC or PET and the copolymers generated by transesterification increases with time. (4) DSC results are consistent with results obtained by SANS, but the latter is more sensitive than the former and differentiates the structural change at different length scales caused by phase separation and transesterification. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0021-8995
    Keywords: 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: A new approach, plasma-induced graft polymerization of poly(ethylene glycol) methacrylate (PEGMA), was used to introduce PEG graft chains with hydroxyl end groups onto a polyurethane (Tecoflex) surface. After argon plasma treatment and subsequent exposure to air, graft polymerization onto Tecoflex films was allowed to proceed in deaerated aqueous solutions of PEGMA at 60°C. The virgin, plasma-treated, and grafted films were characterized comparatively by means of attenuated total reflection infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, measurement of contact angle, and protein adsorption. The Tecoflex film undergoes etching during argon plasma treatment, surface oxidation when exposed to air after plasma treatment, and surface restructuring in response to environment upon storage in air. The plasma-induced graft polymerization of PEGMA proved to be successful in introducing PEG graft chains with reactive hydroxyl end groups onto the surface. Grafted films with different surface grafting density of PEG were prepared. Grafted films with higher PEG content exhibit higher hydrophilicity, smoother topography, and lower fibrinogen adsorption. The hydroxyl end groups built onto the surface offer further possibilities of improving its biocompatibility by immobilizing bioactive molecules. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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