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  • 1
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(L-milchsäure) ist ein biokompatibler, semikristalliner, thermoplastischer Polyester mit ungünstigen mechanischen Eigenschaften. Daher wurde in einem “reactive blending”-Prozeß ein Acrylkautschuk, n-Butylacrylat, mittels einer Suspensionspolymerisation in Wasser auf in einem organischen Lösungsmittel gelöste Poly(L-milchsäure) gepfropft. Die gebildeten Copolymeren konnten isoliert und durch NMR-Spektroskopie und DSC-Messungen charakterisiert werden. Die Untersuchung der mechanischen Eigenschaften ergab keine befriedigenden Ergebnisse, weil die Kautschukphase wahrscheinlich aus viskosen linearen Makromolekülen besteht und daher keine elastischen Eigenschaften besitzt. In weiteren Arbeiten soll der Syntheseweg so modifiziert werden, daß durch den Einbau von Diacrylaten eine zumindest partielle Vernetzung der Kautschukphase erreicht wird.
    Notes: Poly(L-lactic acid) is a biocompatible polyester, semicrystalline, thermoplastic, with low versatility in mechanical properties. To overcome this problem, a reactive blending procedure was performed by grafting an acrylic rubber, n-butyl acrylate, via water suspension polymerization onto poly(L-lactic acid) dissolved in an organic solvent. It was possible to isolate the copolymeric phase formed from the two polymers and characterize it by using NMR and DSC techniques. Mechanical tests on blends gave no satisfactory response, probably because the rubbery phase is composed essentially of viscous linear macromolecules, not able to perform elastic properties. Work is in progress to modify the synthetic pathway to incorporate diacrylates in order to realize a rubbery phase at least partially cross-linked.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 883-890 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of two phenylated bifunctional monomers, dimethyl 4-(4-(p-aminophenoxy)phenyl)-3,5,6-triphenylphthalate and dimethyl 4-(4-(4-(p-aminophenoxy)phenoxy)phenyl)-3,5,6-triphenylphthlate, was accomplished. Polymerization in solution or by a bulk polymerization procedure yielded a series of low molecular weight phenylated polyimides. The polymers were soluble in chlorinated hydrocarbons and exhibited thermal stabilities comparable to other polyimide systems.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 2579-2587 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By coupling the evolved gas detection method with various analysis methods, the thermal decomposition products of the statistical vinyl alcohol/vinyl acetate copolymers were analysed.The data are presented comparatively with those obtained for the corresponding block copolymers of the same composition.The differences in the nature and amounts of the reaction products are explained by the structural characteristics of the copolymers.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 1639-1647 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermoxidative behavior of atactic and isotactic polypropylene under dynamical thermoxidative conditions has been studied. It has been established that, with the increase of the heating rate, the development of the oxidative processes are diminished and consequently a modification in the reaction mechanism takes place. One can notice at the same time that the oxidative processes are more intense in the case of the atactic polymer. The 5-15°C/min heating rates determine significant differences between the thermal behavior of the samples, permitting the elaboration of the standard curves useful in fast determination of the atactic content of the industrial products by routine analysis.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 509-516 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acid hydrolysis of a stereoblock poly(methyl methacrylate) sample leads to a mixture of isotactic and syndiotactic poly(methacrylic acid) which can be separated by electrophoresis. The experiment confirms the stereochemical identity between the so-called “stereoblock” poly(methyl methacrylate) and the stereocomplex which syndiotactic and isotactic poly(methyl methacrylate) form in the ratio 2:1. A possible mechanism of replica polymerization is suggested to account for this effect.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a combination of one- and two-dimensional methods, 1H- and 15N-nmr spectroscopy has been employed to perform the complete assignment and the structural determination of the immunogenic undecapeptide CTTTNSRGTTT in DMSO solution. Nuclear Over-hauser enhancement spectroscopy experiments indicated the presence of secondary structures, mainly turn-like structures, which only represent a family, albeit a dominant one, of an ensemble of conformations available to the peptide. Since reverse turns may play an important role as intermediates in protein folding, the experimental observations described here may link the immunological and theoretical approaches to protein folding.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibacterial properties of the secretion from the female reproductive accessory glands of medfly Ceratitis capitata are mostly ascribed to the presence of two peptides, ceratotoxin A and B, which exhibit a strong activity against gram-positive and gram-negative bacterial strains, and show sequence and function homology with cecropins, melittin, and magainins.CD experiments performed in different solvents indicate the presence of a significant content of helical structures in organic solvent.Two-dimensional nmr results for ceratotoxin A in methanol show a helical behavior for the 8-25 region of the peptide. A Ramachandran classification of each residue for the structures obtained from distance geometry calculations lead to the definition of four structural families in which the central segment 10-19 is always helical and differences refer to residues 8-9 and 19-23.A sequence analysis of the two ceratotoxins and a systematic search on the protein data bank revealed the occurrence of a KX-hydrophobic-hydrophobic-P motif that seems to be important for helix stabilization. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD and nmr characterizations are reported for the 23-mer peptide CMC3, corresponding to residues 577-599 of gp41, the transmembrane glycoprotein of the human immunodeficiency virus 1. Concentration, temperature, and pH dependencies of CD and nmr spectra are indicative of self-association with a consequent stabilization of secondary structural elements in water. The addition to the water solution of small amounts of trifluoroethanol induces a secondary structure, mostly due to the presence of helical elements. The amphipathic character of the helix and the presence of three hydrophobic 4/3 heptad repeats suggest that the peptide could be structured in a symmetric association of helices, such as in a coiled-coil structure. This behavior is discussed in terms of a possible role of this segment in the gp41 envelope oligomerization. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Endorphin has been studies iin SDS micelles by one- and two-dimensional nmr spectroscopy (1D and 2D nmr), and to explore the influence of peptide length and composition on the polypeptide structure, the investigation was extended to a number of fragments. The nmr results are compared with those obtained from CD experiments and discussed in terms of a secondary structure that involves the central region of β-endorphin.
    Additional Material: 11 Ill.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combined use of several nuclear magnetic resonance and restrained molecular dynamics techniques allowed the formulation of a molecular model for the preferred solution conformation of a synthetic peptide reproducing the [1-20] processing domain of the pro-ocytocin-neurophysin precursor. In the model, the conformation of the 20-membered tocin ring, with the two Cys1 and Cys6 residues bridged by a disulphide bond, is very close to that observed for isolated ocytocin in the solid state; in addition, a type II β-turn is postulated for the 7-10 segment of the acyclic tail containing the Lys11-Arg12 processing site, and connecting ocytocin to the neurophysin domain, while the C-terminal 13-20 segment of the molecule is believed to assume a helical structure. This particular structural organization could be important in participating as the favorable conformation for optimal substrate-enzyme active site recognition and processing by specific endoproteases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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