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  • AERODYNAMICS  (37)
  • Polymer and Materials Science  (27)
  • EARTH RESOURCES AND REMOTE SENSING  (11)
  • 1985-1989  (75)
  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An intercalation model of a complex between DNA and a bleomycin fragment (BLMF), consisting of the bithiazole core and an amide and a protonated amino substituent, is presented. The model, which shows a preference for BLMF with the protonated amine in the minor groove and the acetyl terminal inserted into either the minor and major grooves, respectively, agrees with recently obtained nmr data. The selection of sites I and II, which have the smallest unwinding of the three theoretical intercalation sites, is consistent with the experimental unwinding angle of 12°. The bithiazole moiety stacks between two base pairs of the double helix, while the protonated substituent interacts ionically with the negatively charged regions of the backbone in the minor groove of the DNA. The protonated amine also forms an intramolecular hydrogen bond with the carbonyl oxygen of the amide group on the same substituent. Analysis of drug complexes with different base-pair sequences reveal four energetically defined groups. The relative energy of the dimer duplex complexes of BLMF correlates with bleomycin's observed base-sequence specificity upon cleavage. The most stable intercalation complexes form adjacent to the bases cleaved most readily. This correlation suggests a primary connection between intercalation and cleavage. A model cleavage site based on these preliminary theoretical calculations and the experimental observations is proposed. It consists of an intercalation site in a trimer duplex. Pyrimidine(p)purine sequences are the predominant sites for intercalation, and the base adjacent to the site at the (3′) end is cleaved.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 463-480 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Secondary-structure prediction has been used to investigate the conformation of the N- and C-terminal telopeptides for type I and type III collagen. The three predictive methods (Chou and Fasman, Robson and co-workers, Lim) indicate mainly aperiodic conformations. A common structural motif is provided by the positioning of β-turns, particularly in the vicinity of the residue sites involved in intermolecular cross-links. An alternative model to that of Helseth et al [(1979) Biopolymers 18, 3005-3014] for the secondary structure of the N-terminal telopeptide of type I collagen is proposed. The general features of these two contrasting structures have been surveyed by model-building techniques employing molecular graphics and energy minimization. The role of the telopeptide component in the structural design of the biomaterial collagen is assessed. Notably, the alternative model clearly serves to demonstrate the compatibility of current cross-linking evidence with the quasi-hexagonal model for the packing of molecules within a collagen fibril.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 3113-3149 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spontaneous polymer formed from 3-hydroxyoxetane (HO), as first reported by Wojtowicz and Polak, is linear, low molecular weight, water-soluble, atactic, poly(3-hydroxyoxetane) (PHO) of high crystallinity with —OCH2CH(OH)CH2OH end units. The highly crystalline nature of this atactic polymer may be related to the crystalline nature of atactic poly(vinyl alcohol) since PHO can be considered a copolymer of vinyl alcohol and formaldehyde. Spontaneous PHO apparently is formed in a cationic polymerization by the carboxylic acids produced by the air oxidation of HO on standing at room temperature for several months. The polymerization can be duplicated by the addition of 2% hydroxyacetic acid to HO. The rate of this unusual cationic polymerization increases greatly with acid strength, e.g., trifluoromethanesulfonic acid reacts explosively with pure HO. A mechanism is proposed for this cationic polymerization. High molecular weight, water-soluble, linear atactic, and highly crystalline PHO (mp = 155°C) was made by polymerizing the trimethylsilyl ether of HO with the i-Bu3Al-0.7 H2O cationic catalyst followed by hydrolysis. Two 1H-NMR methods for measuring the tacticity of PHO were developed based on finding two different types of methylene units at 400 MHz with the methine protons decoupled. Also, an 1H-NMR method was developed for measuring branching in HO polymers. High molecular weight, linear PHO with enhanced isotacticity (80%) has been obtained in low yield as a water-insoluble fraction with Tm = 223°C. The low molecular weight PHO prepared previously by the base-catalyzed, rearrangement polymerization of glycidol is highly branched.
    Additional Material: 16 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 111-125 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have prepared a number of high molecular weight, soluble, symmetrical dialkyl substituted germanium homopolymers and germanium-silicon copolymers. In solution, the absorption of the homopolymers was ∼ 20 nm red shifted from the crossponding silicon derivatives. This was somewhat unexpected based on theoretical predictions and has been rationalized on the basis of conformational arguments. In the solid state, samples of poly(di-n-hexylgermane) and poly(di-n-octylgermane) are strongly thermochromic. The effect is attributed to the conformational locking of the backbone which is caused by the crystallization of the side groups. In this regard, the germanium derivatives behave similarly to the corresponding silicon polymers, and the convergence of the long wavelength absorptions for both types of polymers is consistent with theoretical predictions. The germanium-silicon copolymers are also strongly thermochromic, but the long wavelength absorption is somewhat blue shifted (8 nm) from the respective homopolymers. As expected, the new germanium homo and copolymers are quite sensitive to light and readily undergo chain scission to produce lower molecular weight materials.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 321-326 
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 219-221 
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 1 (1989), S. 140-141 
    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
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 1 (1989), S. 239-240 
    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
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Structure efficiency relationships of corrosion inhibitors for oil and gas productionStructure efficiency relationships for quarternary ammonium compounds as corrosion inhibitors for oil and gas production were investigated in the system mild steel/aqueous NaCl solution (5 weight%, CO2 saturated) at T = 298 K and T = 343 K by Electrochemical Impedance Spectroscopy (EIS) and weight loss measurements. In-situ EIS measurements rapidly gave relatively accurate results on differential inhibitor efficiencies. Composition, thickness and inhibitor content of the inhomogeneous 3-D protecting layers formed on highly pure iron surfaces were determined by XPS measurements. The inhibition mechanism of the inhibitor used could be determined by its distribution within the 3-D protecting surface layer and is interpreted in terms of the interphase inhibition concept.
    Notes: Struktur-Wirkungs-Prinzipien von quartären Ammoniumverbindungen als Korrosionsinhibitoren für die Rohöl- und Erdgasförderung wurden anhand von Elektrochemischer Impedanz Spektroskopie (EIS) und Gewichtsverlustmessungen in Systemen C-Stahl/wäßrige NaCl-Lösung (5 Gew.%, CO2-gesättigt) bei T = 298 K und T = 343 K untersucht. Es konnte gezeigt werden, daß in-situ EIS Messungen rasch relativ genaue Resultate über differentielle Inhibitorwirksamkeiten liefern. Aus XPS Untersuchungen an Oberflächen aus Reinsteisen ließen sich Zusammensetzung, Dicke und Inhibitorgehalt der sich auf dem Substrat bildenden inhomogenen 3-D Deckschichten bestimmen. Der Wirkungsmechanismus des verwendeten Inhibitors konnte aus seiner Verteilung innerhalb der 3-D Deckschicht mit dem Konzept der Interphaseninhibition gedeutet werden.
    Additional Material: 6 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
    Additional Material: 4 Ill.
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