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  • 1
    Electronic Resource
    Electronic Resource
    Bright field image of banded texture in lyotropic liquid crystals of a polydiacetylene (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1289-1297 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Formation of a banded texture was observed in thin films of a polydiacetylene prepared from the lyotropic nematic phase subject to flow. The banded texture was experimentally investigated by polarizing light microscopy and transmission electron microscopy. The banded structure is initially formed in a nematic phase of the polymer and could be imaged by TEM after its transformation to a lamellar phase which is the polymer analogon to a smectic phase in low-molecular-weight compounds. A mathematical description of the texture is given. During further relaxation of the system in the lyotropic state the initial orientation is lost by the formation of disclinations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940503
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  • 2
    Electronic Resource
    Electronic Resource
    A kinetic model for steric hindrance effects on quaternization of poly(vinylpyridines) (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 3453-3464 
    Details
    ISSN: 0887-624X
    Keywords: quaternization ; poly(vinylpyridines) ; alkyl halide ; kinetics ; steric hindrance ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quaternization reactions of poly(vinylpyridines) with alkyl halides show retardation in excess of that predicted by the classical second-order kinetics. Based on the classical collision and transition state theories, a kinetic model has been developed to quantify such retardation, in which the overall reaction rate is characterized by a rate constant k0 of the intrinsic reactivity between a pyridyl group and an alkyl halide group, and by a steric hindrance effect parameter α. The latter accounts for the degree to which the rate of collisions of reactants is reduced, or to which the freedom of movement of the reactants in the transition state is restricted as the reaction proceeds. The resulting kinetic expression has been validated using experimental results reported in the literature and those of our own. The functional dependence of k0 and α values on the nature of poly(vinylpyridines) and that of alkyl halides is explained. Other factors affecting k0 and α, including changes in macromolecular dimensions and/or in the distribution of residue environment, quality of solvent, and reaction temperature, are discussed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1993.080311335
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  • 3
    Electronic Resource
    Electronic Resource
    Fluorophore-labeled carbohydrate analysis of immunoglobulin fusion proteins: Correlation of oligosaccharide content with in vivo clearance profile (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 405-405 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260470314
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic interaction in an amide containing two separate nitroxyl radicalsThe authors are grateful to Dr. J. Lin of the Max-Planck-Institut für Festkörperforschung and H. Theuss of the Max-Planck-Institut für Metallforschung in Stuttgart for the susceptibility measurements and to Dipl. Chem. A. Gittinger for his help in preparing the manuscript. [AMC 117] (1992)
    Weinheim : Wiley-Blackwell
    Advanced Materials 4 (1992), S. 349-351 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19920040506
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  • 5
    Electronic Resource
    Electronic Resource
    Photochemical synthesis of polyacrylate-silica hybrid sol-gel materials catalyzed by photoacidsThis work was supported by the National Institutes of Health (Grant No. RO1-DE09848). YW is grateful to E. I. Du Pont de Nemours & Company, Inc. for a Young Faculty Award. We thank Professor a. W. Addison of Drexel University for many valuable discussions. (1994)
    Weinheim : Wiley-Blackwell
    Advanced Materials 6 (1994), S. 372-374 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19940060505
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  • 6
    Electronic Resource
    Electronic Resource
    A dynamic laser light-scattering study of chitosan in aqueous solution (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 385-392 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution behavior of four chitosans (91% deacetylated chitin) with different molecular weights in 0.2M CH3COOH/0.1M CH3COONa aqueous solution was investigated at 25°C by dynamic laser light scattering (LLS). The Laplace inversion of the precisely measured intensity-intensity lime correlation function leads us to an estimate of the line-width distribution G(Γ), which could be further reduced too translational diffusion coefficient distributions G(D). By using a combination of static and dynamic LLS results, i.e., Mw and G (D), we were able to establish a calibration of D = kDM-αD with kD = (3.14 ± 0.20) × 10-4 and αD = 0.655 ± 0.015. By using this calibration, we successfully converted G(D) into a molecular weight distribution fw(M). The larger αD value confirms that the chitosan chain is slightly extended in aqueous solution even in the presence of salts. This is mainly due to its backbone and polyelectrolytes nature. As a very sensitive technique, our dynamic LLS results also revealed that even in dilute solution chitosan still forms a small amount of larger sized aggregates that have been overlooked in previous studies. The calibration obtained in this study will provide another way to characterize the molecular weight distribution of chitosan in aqueous solution at room temperature. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350406
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  • 7
    Electronic Resource
    Electronic Resource
    Elastic constant anisotropy, core structure of wedge disclinations and optical texture of main-chain P-4-BCMU liquid crystals (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2171-2186 
    Details
    ISSN: 0887-6266
    Keywords: P-4-BCMU ; lyotropic liquid crystalline polymer ; elastic constant anisotropy ; core structure ; wedge disclinations ; optical texture ; TEM ; polarizing light microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The elastic constant anisotropy and the core structure of wedge disclinations with strengths s = ±½ of lyotropic liquid crystals of a soluble polydiacetylene, P-4-BCMU (Mw = 5.15 × 105, Mn = 2.16 × 105, and Mw/Mn = 2.4), in chloroform was studied. The Frank elastic constant anisotropy defined by ε = (k11 - k33)/(k11 + k33) for this polymer was determined by three different methods. The results show that the value of ε for this polymer is 0.5 (±0.05) in solid state and/or in liquid crystal state, indicating that the splay constant k11 is three time higher than the bend constant k33. This result further implies that splay is unfavorable in the liquid as it requires greater energy than bend. In the area adjacent to the core of a singularity the value of ε increases with decreasing distance to the core, indicating increasing anisotropy of the elastic constants toward the core. The influence of the elastic constant anisotropy on the optical texture of the LC polymer when viewed by polarizing light microscope is studied. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321305
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  • 8
    Electronic Resource
    Electronic Resource
    Fluorophore-labeled carbohydrate analysis of immunoglobulin fusion proteins: Correlation of oligosaccharide content with in vivo clearance profile (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 399-407 
    Details
    ISSN: 0006-3592
    Keywords: sialic acid ; in vivo clearance ; electrophoresis of carbohydrates ; adhesion molecules ; CTLA4 ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: CTLA4 is a membrane receptor on cytotoxic T cells whose interaction with the B7 counterreceptor on B cells is important in alloantigen responses. Soluble recombinant human and murine CTLA4 were produced using either Chinese hamster ovary or NS-0 cell lines. Expression vectors were constructed containing the gene coding for the extracellular domain of CTLA4 fused to either human lgG1 hinge, CH2, and CH3 domains or murine lgG2a hinge, CH2, and CH3 domain genes. These glycoproteins were produced in hollow-fiber or packed-bed-type bioreactors and purified from conditioned media by protein A affinity chromatography. Batches of purified CTLA4lg were analyzed for size, composition, and isoelectric point (pl) patterns by standard protein methods; oligosaccharide and monosaccharide profiles using several carbohydrate specific techniques; and in vivo clearance profiles using a murine model. Significant differences were observed between lots in their pl, clearance, and crbohydrate profiles. Higher overall pl values correlated with accelerated α-phase clearance and changes in oligosaccharide composition as determined by lectin binding analysis and electrophoresis of fluorophore-conjugated carbohydrates. Preparations exhibiting slower clearance profiles had oligosaccharides with higher quantities of N-acetylneuraminic acid and were predominantly of an N-linked biantennary complex-type. Conversely, batches with accelerated clearance profiles had less detectable N-acetylneuraminic acid. Oligosaccharides from murine CTLA4lg produced in NS-0 cells had terminal N-glycolylneuraminic acid but no detectable N-acetylneuraminic acid and had concomitant accelerated clearance. These data suggest that the presence and quantity of N-acetylneuraminic acid is an important component in predicting CTLA4lg plasma clearance rates and that production lots can be analyzed for oligosaccharide heterogeneity and sialic acid content by electrophoresis of fluorophore-conjugated carbohydrates. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460502
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  • 9
    Electronic Resource
    Electronic Resource
    Microscopic observations of the different morphological changes caused by anti-bacterial peptides on Klebsiella pneumoniae and HL-60 leukemia cells (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 413-425 
    Details
    ISSN: 1075-2617
    Keywords: modes of action ; anti-bacterial ; cecropins ; morphology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural anti-bacterial peptides cecropin B (CB) and its analogs cecropin B-1 (CB-1), cecropin B-2 (CB-2) and cecropin B-3 (CB-3) were prepared. The different characteristics of these peptides, with amphipathic/hydrophobic α-helices for CB, amphipathic/amphipathic α-helices for CB-1/CB-2, and hydrophobic/hydrophobic α-helices for CB-3, were used to study the morphological changes in the bacterial cell, Klebsiella pneumoniae and the leukemia cancer cell, HL-60, by scanning and transmission electron microscopies. The natural and analog peptides have comparable secondary structures as shown by circular dichroism measurements. This indicates that the potency of the peptides on cell membranes is dependent of the helical characteristics rather than the helical strength. The microscopic results show that the morphological changes of the cells treated with CB are distinguishably different from those treated with CB-1/CB-2, which are designed to have enhanced anti-cancer properties by having an extra amphipathic α-helix. The morphological differences may be due to their different modes of action on the cell membranes resulting in the different potencies with lower lethal concentration and higher concentration of 50% inhibition (IC50) of CB on bacterium and cancer cell, respectively, as compared with CB-1/CB-2 (Chen et al. 1997. Biochim. Biophys. Acta 1336, 171-179). In contrast, CB-3 has little effect on either the bacterium or the cancer cell. These results provide microscopic evidence that different killing pathways are involved with the peptides. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Polyphosphazene membranes. I. Solid-state photocrosslinking of poly[(4-ethylphenoxy)-(phenoxy)phosphazene] (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1607-1617 
    Details
    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: Dense films of poly[(4-ethylphenoxy)(phenoxy)phosphazene] (PEPP), a potentially attractive ion-exchange membrane material, were crosslinked to varying degrees using UV light and a photoinitiator. This polymer contained two kinds of substituents: phenoxy groups to be used for possible functionalization (e.g., sulfonation) and ethylphenoxy side-chains for photocrosslinking, where hydrogens at the benzylic carbons could be abstracted by a photoinitiator-leaving macroradicals that after recombination formed covalent bonds. The polyphosphazene polymer was synthesized, mixed with a photoinitiator, shaped into a thin film by solvent casting, and irradiated with UV light for a specified period of time. Benzophenone (BP), was selected as the photoinitiator because it was miscible with poly-phosphazene, had the highest rate of hydrogen abstraction, and absorbed UV light of 365 nm wavelength. The half-life of benzophenone in 50 μm-thick irradiated films was determined to be 20 min. When the BP-PEPP molar ratio was increased from 0 to 0.5, the glass transition temperature increased after irradiation from -8.8 to 53.5°C. At the same time, the equilibrium swelling in dimethylacetamide, at 25°C, decreased from infinity to 0.31. Tensile strength tests of the crosslinked films revealed a nonlinear dependence on BP-PEPP molar ratio. © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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