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  • Chemistry  (6)
  • 1990-1994  (6)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Quantitative time-of-flight secondary ion mass spectrometry of a perfluorinated polyether (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 17 (1991), S. 125-136 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Quantitative determination of the molecular weight and composition of submicrogram of a perfluorinated polyether (PFPE) supported on Ag and Si substrates was from empirical relationships derived from the intensities of specific high-mass (≥ 800 amu) fragmentation ions from time-of-flight secondary ion mass spectrometry (TOF-SIMS) measurements. These relationships are explained in terms of simple concepts regarding the process of volatilization, fragmentation and ionization in TOF-SIMS. The results for both negative and positive ions are nearly independent of the substrate materials used, demonstrating that the high-mass fragmentation ions in TOF-SIMS may be useful generally for in situ quantitative analysis of PEPEs on non-specific substrates. This is an important difference between the TOF-SIMS fragmentation spectrum and the complementary TOF-SIMS cationized molecular ion spectrum, which requires special sample preparation and/or substrates. In order to interpret the quantitative information available in the TOF-SIMS fragment spectrum, it was absolutely necessary to characterize extensively the PFPE samples using NMR and TOF-SIMS Ag+ -cationized molecular ion results. This characterization helped to demonstrate the power of TOF-SIMS to do quantitative analysis and led to additional insight concerning the SIMS ion-forming process for PFPE. This study represents one of the first attempts to make quantitative use of the high-mass fragment ion intensities in SIMS studies of polymers, and presents a method for confirming the origin of the mass peaks in the spectra.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740170303
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  • 2
    Electronic Resource
    Electronic Resource
    Altered protein synthesis in rat kidney cells exposed to semiconductor materials (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 8 (1994), S. 253-258 
    Details
    ISSN: 0268-2605
    Keywords: Arsenite ; arsenic ; gallium ; indium ; kidney tubule epithelial cells ; primary culture ; heat-shock protein ; stress protein ; semiconductor ; rat ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III-V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [35S]methionine. A protein with a molecular weight (Mr) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with Mr values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aoc.590080316
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  • 3
    Electronic Resource
    Electronic Resource
    Polymer concrete and polymer mortar using resins based on recycled poly(ethylene terephthalate) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1649-1655 
    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: Fundamental properties of polymer concrete (PC) and polymer mortar (PM) made from unsaturated polyester resins based on recycled poly(ethylene terephthalate), PET, are described. Mechanical properties investigated include strength, modulus of elasticity, ductility index, Poisson's ratio, coefficient of thermal expansion, shrinkage, and exotherm. Durability properties include chemical resistance, water absorption, sand-blast resistance, and thermal cycles of thin overlays on portland cement concrete slabs. Resins based on recycled PET offer the possibility of a lower source cost for forming useful PC and PM (PC/PM) based products. The recycling of PET in PC and PM would also help alleviate an environmental problem and save energy.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440919
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  • 4
    Electronic Resource
    Electronic Resource
    Depressant insect selective neurotoxins from scorpion venom: Chemistry, action, and gene cloning (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 22 (1993), S. 55-73 
    Details
    ISSN: 0739-4462
    Keywords: polypeptides ; insect selectivity ; neuromuscular effects ; sequence ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The present study examines the similarity in the symptoms and binding properties between the depressant and excitatory insect-selective neurotoxins, derived from scorpion venom. A comparison of their primary structures and neuromuscular effects is presented. A new depressant toxin (LqhlT2) was purified from the venom of the scorpion Leiurus quinquestriatus hebraeus. The effects of this toxin on a prepupal housefly neuromuscular preparation mimic its effects on the intact insect, i.e, a brief period of repetitive bursts of regular junction potentials (JPs) is followed by reduced amplitude JPs ending with a block of the neuromuscular transmission. “Loose” patch clamp recordings indicate that the repetitive activity has a presynaptic origin (the motor nerve) and resembles the effect of the excitatory toxin AalT. The final synaptic block is supposed to be the end result of neuronal membrane depolarization. Such an effect is not caused by an excitatory toxin, which induces long ‘trains’ of repetitive firing. The amino acid sequences of three depressant toxins were determined by automatic Edman degradation indicating a high degree of sequence homology. This conservation differs from those of other groups of scorpion toxins. The opposing pharmacological effects of depressant toxins are discussed in light of the above neuromuscular effects and sequence analysis. A genetic approach in the study of the structure-function relationships of the depressant toxins was initiated by isolating cDNA clones encoding the LqhiT2 and BjlT2 toxins. Their sequence analysis revealed the precursor form of these toxins: A 21 amino acid residue signal peptide followed by a 61 amino acid region of the mature toxin, and three additional amino acids at the carboxy terminus. © 1993 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940220107
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  • 5
    Electronic Resource
    Electronic Resource
    Development of recombinant viral insecticides by expression of an insect-specific toxin and insect-specific enzyme in nuclear polyhedrosis viruses (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 22 (1993), S. 315-344 
    Details
    ISSN: 0739-4462
    Keywords: Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: As supplements to classical chemical insecticides, two approaches to develop recombinant baculovirus insecticides are described. In one approach an insect-specific toxin is expressed leading to a dramatic reduction in time to death. In the second approach an insect juvenile hormone esterase is expressed which leads to a reduction in feeding. Modifications of the wildtype esterase led to viruses which reduced the time to death as efffectively as did the toxin-expressing virus. In both cases existing recombinant viruses are viewed as leads, and approaches to further improvement in the engineered viruses are suggested. Many of these approaches are based on analogy with the development of classical synthetic insecticides. Using these viruses as examples, the potential utility and limitations of recombinant viruses and other biological insecticides are discussed. © 1993 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940220303
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrogen-1 and aluminum-27 NMR study of Al(ClO4)3 in aqueous mixtures of dimethylformamide and urea (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 280-286 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 27Al NMR ; Al(ClO4)3 in aqueous dimethylformamide and urea ; Proton and ligand exchange ; Low-temperature studies ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A competitive solvation study of Al(III) in water-dimethylformamide (DMF) and water-urea mixtures was carried out by 1H and 27Al NMR spectroscopy. At temperatures low enough to slow proton and ligand exchange, separate 1H resonance signals were observed for bulk and coordinated ligand molecules, and for 27Al in different solvation complexes. The 1H NMR data confirmed hexacoordination of Al(III) at all concentrations, monodentate binding at the oxygen atom of both DMF and urea, preferential solvation by both organic ligands, the presence of steric hindrance to complexation, particularly by DMF, and the identification of the complexes responsible for the 27Al spectra. It also showed a non-equivalence of the amido groups in urea, in both the complex and free states, presumably owing to hindered rotation about the carbon - oxygen bond. In contrast to previous reports, the 27Al spectra for the water-DMF and water-urea solutions showed well resolved signals for the species [Al(H2O)n-6Ln]3+ (n = 0-6; L = DMF or urea), including two isomers for one of the water-urea complexes. The 27Al NMR data reflected the stronger preferential solvation by urea.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300403
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