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  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C-terminal analogues of neuropeptide Y (NPY) of small molecular size have been synthesized. The influence of chain length, single or multiple amino acid substitution, and segment substitutions on receptor binding, pre- and postsynaptic biological activity, and conformational properties have been investigated. Receptor binding and in vivo assays revealed biological activity for NPY Ac-25-36 that increased with increasing α-helicity. In attempts to stabilize the α-helical content, three independent types of modified NPY Ac-25-36 analogues were synthesized. Strong agonistic activities could be detected in a series of discontinuous analogues, which are constructs of N-terminal parts linked via different spacer molecules to C-terminal segments. One of the most active molecules was NPY 1-4-Aca-25-36 (Aca, ε-aminocaproic acid). For the first time conformational properties of a series of small NPY analogues have been investigated by CD, and correlated with biological activity and receptor binding. A C-terminal dodecapeptide segment of NPY with an amount of 50% substitution to the native C-terminal sequence of NPY was found to exhibit significant receptor binding.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 123-142 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Secondary structure investigations, affinities, and activities of neuropeptide Y analogues with respect to the Y1 and the Y2 receptor are reviewed. The results are discussed with respect to the different prerequisites for affinities to both receptor subtypes. The results from a systematic scanning of the hormone using L-alanine and from a large variety of discontinuous and cyclic analogs suggest that two different conformations of neuropeptide Y are adopted at the Y1 and Y2 receptors. Whereas a C-terminal turn structure is suggested for Y1 receptor affinity, an α-helical conformation of the C-terminus is afforded for good binding to the Y2 receptor. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new approach for evaluating the secondary structure of proteins by CD spectroscopy of overlapping peptide segments is applied to porcine adenylate kinase (AK1) and yeast guanylate kinase (GK3).One hundred seventy-six peptide segments of a length of 15 residues, overlapping by 13 residues and covering the complete sequences of AK1 and GK3, were synthesized in order to evaluate their secondary structure composition by CD spectroscopy.The peptides were prepared by solid phase multiple peptide synthesis method using the 9-fluorenylmethoxycarbonyl/tert-butyl strategy. The individual peptide secondary structures were studied with CD spectroscopy in a mixture of 30% trifluoroethanol in phosphate buffer (pH 7) and subsequently compared with x-ray data of AK1 and GK3.Peptide segments that cover α-helical regions of the AK1 or GK3 sequence mainly showed CD spectra with increasing and decreasing Cotton effects that were typical for appearing and disappearing α-helical structures. For segments with dominating β-sheet conformation, however, the application of this method is limited due to the stability and clustering of β-sheet segments in solution and due to the difficult interpretation of random-coiled superimposed β-sheet CD signals.Nevertheless, the results of this method especially for α-helical segments are very impressive. All α-helical and 71% of the β-sheet containing regions of the AK1 and GK3 could be identified. Moreover, it was shown that CD spectra of consecutive peptide content reveal the appearance and disappearance of α-helical secondary structure elements and help localizing them on the sequence string. © 1997 John Wiley & Sons, Inc. Biopoly 41: 213-231, 1997
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 54 (1982), S. 530-531 
    ISSN: 0009-286X
    Keywords: Elektrochemie ; Festbett-Elektroden ; Graphit ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 54 (1982), S. 809-817 
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: New battery systems. The reversible storage of electrical energy plays a central role in the development of electric vehicles, load levelling in power stations, and technical utilization of solar energy. Electrochemistry offers interesting solutions with optimal energy density; however, these have reached technical maturity in only a few cases. The conventional lead/acid accumulator is being further improved among aqueous systems. Moreover, various other lines of development have been initiated in recent years, such as nickel/zinc and chlorine/zinc accumulators, which offer totally fresh perspectives from an electrochemical and engineering point of view. In the case of zinc/air and aluminium/air batteries, external redeposition of the metal is envisaged. From a practical point of view, aqueous systems are unsurpassable. Metals with an extremely high negative potential like sodium or lithium can only be cycled in the absence of water. Systems with molten salts or solid electrolytes do not suffer from this drawback. The sodium/sulfur battery, which is characterized by readily available cell components of low environmental impact, is presently undergoing intensive development. However, thermal discharge represents a technical problem. The future of these new developments will be governed by their economics, energy density, energy efficiency, power density, and last but not least by their cyclability. These properties have not yet been optimized in a single system.
    Additional Material: 15 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyvinylpyridines activated by tris(π-allyl)chromium and by tetrakis (σ-allyl)molybdenum or tetrakis(σ-allyl)tungsten, complexed with tetrahydrofuran, were used for grafting with acrylonitrile. The products obtained, differing in the degree of branching, were characterized by various physical methods. Block copolymers of the types butadiene-acrylonitrile and styrene-oligobutadiene-acrylonitrile were synthesized by the use of tris(π-butadienyl)chromium as the initial active agent. Some molecular parameters of these block copolymers were established.
    Additional Material: 4 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 2725-2739 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The galvanostatic electropolymerization of thiophene (1), 3-methylthiophene (2) and 2,2′-bithiophene (3) in acetonitrile, containing 0,002 to 20 mol/L water, was studied in detail. The current efficiency γ for the polymer film formation decreased rapidly for 1, but much slower for 2 and 3 with increasing water concentration cH2O. For cH2O = 0,1 mol/L, γ was found to be 10, 82 and 95% for 1-3. It was possible to describe the experimental γ vs. cH2O plots quantitatively by a model where the electrogenerated radical cations (rc) of the thiophene (derivative) are consumed by two competing second-order follow up reactions, the nucleophilic attack of the rc by water (i) and the rate-determining dimerization of two rc's (ii). Their rates are given by: (i) v1 = k1 crc cH2O and (ii) v2 = k2 c2rc. The side reaction (i) leads to soluble products, while reaction (ii) contributes to the polymer film growth. The ratio k1/k2 was found to be 3 · 10-7, 2 · 10-8 and 4 · 10-9 for 1, 2 and 3, respectively, and this shows that the electropolymerization of 2,2′-bithiophene is by a factor of about 100 less sensitive toward the present water than thiophene. The steady state concentration crc is in the order of 10-9 mol/L in all three cases. The relative insensitivity of doping/undoping cycles with respect to the presence of water is discussed in terms of a lessened reactivity of the polarons and a low solubility of water in the heteroaromatic polymer.
    Additional Material: 10 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 631-638 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of basic aluminium dibenzoate upon the supercooling of polypropylene fractions of molecular weight 9.2 × 103-1.25 × 106 was determined by differential thermal analysis. The response to heterogeneous nucleation within the precision of the method used appears to be only slightly dependent, if at all, upon the molecular weight of the polymer.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 673-685 
    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 model nucleating agent for polypropylene crystallization is described. A series of compounds consisting mainly of organocarboxylic acid salts is evaluated as heterogeneous nucleating agent for polypropylene crystallization by measuring their effect upon the polymer supercooling. Sodium benzoate and basic aluminium dibenzoate were among the best nucleating agents found. The nucleating abilities of the various compounds are discussed in terms of their structural features.
    Additional Material: 7 Tab.
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  • 10
    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: The effect of cooling, nucleation, and spherulitic growth rates on the properties of polypropylene is discussed briefly. A differential thermal analysis technique is described for evaluating the relative extent of heterogeneous nucleation that occurs in a particular polypropylene composition. The method is based upon a nucleating agent's ability to reduce the relatively large amount of supercooling that occurs upon crystallization of polypropylene. Compounds are shown to vary widely in their effectiveness as heterogeneous nucleating agents in polypropylene. The relationships between the degree of supercooling of a particular polypropylene composition and its relative clarity, tensile properties, density, and morphology are shown.
    Additional Material: 12 Ill.
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