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  • Chemistry  (47)
  • Surface physics, nanoscale physics, low-dimensional systems  (21)
  • SPACECRAFT PROPULSION AND POWER  (9)
  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of the fluorinated antimalarial drug fluoroquine [7-fluoro-4-(diethyl-amino-1-methylbutylamino)quinoline] with DNA, tRNA, and poly(A) has been investigated by optical absorption, fluorescence, and 19F-nmr chemical-shift and relaxation methods. Optical absorption and fluorescence experiments indicate that fluoroquine binds to nucleic acids in a similar manner to that of its well-known analog chloroquine. At low drug-to-base pair ratios, binding of both drugs appears to be random. Fluoroquine and chloroquine also elevate the melting temperature (Tm) of DNA to a comparable extent. Binding of fluoroquine to DNA, tRNA, or poly(A) results in a downfield shift of about 1.5 ppm for the 19F-nmr resonance. The chemical shift of free fluoroquine depends on the isotopic composition of the solvent (D2O vs H2O). The solvent isotope shift is virtually eliminated by fluoroquine binding to any one of the nucleic acids. 19F-nmr relaxation experiments were carried out to measure the spin-lattice relaxation time (T1), 19F{1H} nuclear Overhauser effect (NOE), off-resonance intensity ratio (R), off-resonance rotating-frame spin-lattice relaxation time (T1ρoff), and linewidth for fluoroquine in the nucleic acid complexes. By accounting for intramolecular proton-fluorine dipolar and chemical-shift anisotropy contributions to the fluorine relaxation, all of the relaxation parameters for the fluoroquine-DNA complex can be well described by a motional model incorporating long-range DNA bending on the order of a microsecond and an internal motion of the drug on the order of a nanosecond. Selective NOE experiments indicate that the fluorine in the drug is near the ribose protons in the RNA complexes, but not in the DNA complex. Details of the binding evidently differ for the two types of nucleic acids. This study provides the foundation for an investigation of fluoroquine in intact cells.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1195-1222 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A build-up technique has been devised that permits prediction of DNA structure form sequence. No experimental information is employed other than the force field parameters. This strategy for dealing with the multiple minimum problem requires a supercomputer to make the necessary global searches. The number of energy minimization trials that were made for each of the 16 deoxydinucleoside monophosphate conformational building blocks of DNA was 1944. As a test case, the minimum energy conformations of d(GpC) and d(CpG) to 5.5 kcal/mole were then combined to generate energy-minimized structures for d(CpGpC). The number of trials that were made for d(CpGpC) was 3752. Minima for this single-stranded trimer to 15 kcal/mole were then employed to search for minimum energy conformations of the duplex d(CpGpC) · d(GpCpG). The number of starting conformations that were utilized at this stage was 1514. The lowest energy duplex had a Z-II-DNA conformation, followed by a B-DNA form at 1.2 kcal/mole. The A- and Z-I-forms as well as many novel Watson-Crick base-paired structures were found at higher energy. Finally, energy-minimized structures of d(CG)6 in Z-II and B-DNA conformations were computed using torsion angles from the analogous duplex trimer minima.
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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: Evidence is presented which shows that hemoglobin S in sickle cells has a tendency to aggregate even in the oxygenated state. The basis for that conclusion is derived from 13C-nmr rotating-frame spin-lattice relaxation studies in the presence of an off-resonance radiofrequency field in which the carbonyl resonances of hemoglobins in erythrocytes are examined. The experiments indicate that the rotational correlation time of hemoglobin S in oxygenated sickle cells at 38°C is 130 nsec compared to a value of 95 nsec for hemoglobin A in normal erythrocytes at the same temperature and the same mean cell hemoglobin content.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 2497-2500 
    ISSN: 0006-3525
    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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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 2747-2750 
    ISSN: 0887-624X
    Keywords: SBR rubber ; crosslinking ; 1,2-bis(benzocyclobutenyl)ethane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Bis(benzocyclobutenyl)ethane (BBCB) was used as a thermally activated crosslinking agent in styrene-butadiene rubber (SBR), both in the raw and carbon black-filled materials. Diels-Alder crosslinking reactions occurred to a significant degree, despite the lack of substituents of opposing electronic effects. The reaction is free of toxic crosslinking promoters and evolved by-products. Various physical properties such as ultimate elongation, tensile strength, and modulus were measured and compared to those properties of a sulfur-cured sample of SBR. Linear relationships were found between the amount of BBCB present and the modulus of the materials, as well as the amount of BBCB and solvent uptake in swell tests. © 1993 John Wiley & Sons, Inc.
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  • 6
    ISSN: 0887-624X
    Keywords: unnatural amino acids ; 5,5,5-trifluoroleucine ; azetidine-2-carboxylic acid ; thiazolidine-4-carboxylic acid ; mono-fluorophenylalanine (o,m,p) ; thienylalanine ; cellfree protein synthesis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability to incorporate unnatural amino acids into biologically synthesized proteins will greatly extend the impact of protein engineering on polymer materials science. The present report describes the use of a rapid cell-free assay to assess the incorporation potential of unnatural amino acids in Escherichia coli. The assay features a coupled transcription-translation system (‘Zubay system’) to screen incorporation of amino acid analogs into plasmid-encoded proteins. Activity estimates are based on the ability of an analog to compete with a radiolabeled natural amino acid, and toxicity effects are screened by monitoring incorporation of a second, unrelated amino acid. The assay was established with analogs known to be active in vivo, using a common bacterial expression vector as template DNA. Positive results were obtained with the leucine analog 5,5,5-trifluoroleucine, the proline analogs azetidine-2-carboxylic acid and thiazolidine-4-carboxylic acid, and three isomers of mono-fluorophenylalanine (o,m,p). No activity was observed for the phenylalanine analogs 2-thienylalanine and 3-thienylalanine. The results suggest that the cell-free assay will be a useful predictor of in vivo incorporation and a useful tool in the design and synthesis of genetically engineered materials. © 1995 John Wiley & Sons, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2817-2824 
    ISSN: 0887-624X
    Keywords: visible light photopolymerization ; tetraorganylborates ; fluorone dyes ; acrylic monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new tetraorganylborate salts have been synthesized and tested as coinitiators with 2,4-diiodo-6-butoxy-3-fluorone (DIBF) for the photopolymerization of acrylic monomer mixtures. The rate of photopolymerization has been found to be a function of chemical structure of the borates. Stability, solubility, and reactivity of these borates as coinitiators for photopolymerization have been investigated. Diphenyldialkylborates have been found to be the best among the tested coinitiators. © 1996 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1667-1677 
    ISSN: 0887-624X
    Keywords: photoinitiator ; iodonium borate salts ; photoinduced radical polymerization ; fluorone dye ; visible polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Iodonium butyltriphenylborate salts (A—I+—Ar′Ph3B-—R), (=Bu) were found to be more efficient than iodonium tetraphenylborate salts (R=Ph) when used as photoinitiators for the polymerization of acrylates. Relative photodecomposition rates were also different. It was found from a study of the photoreaction of iodonium borate salts with a model monomer, methyl methacrylate, that iodonium butyltriphenylborate salts simultaneously produce a butyl radical from the borate anion and an aryl radical from the iodonium cation upon irradiation. Both radicals initiate polymerization. Iodonium tetraphenylborate salts were found to release an aryl radical, but only from the iodonium cation. Iodonium borate salts exhibit strong absorption below 300 nm with a tail absorption above 400 nm. Thus, iodonium butyltriphenyl borate salts are efficient photoinitiators even when used with visible light. When a photosensitizer such as 5,7-diiodo-3-butoxy-6-fluorone is employed, iodonium butyltriphenylborate salts are rendered much more efficient for visible light photopolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1667-1677, 1998
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1341-1348 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An automated distillation sequencing system (DSEQSYS) is presented, which consists of three components: a control program, a fuzzy heuristic synthesis program, and a process simulator. DSEQSYS, when applied to problems previously reported in the literature, overcomes some of the disadvantages of using heuristics or mathematical programming alone. DSEQSYS can address problems involving nonsharp separations, nonideal chemical behavior, and conflicting heuristics. A simple approach for converting the traditional separation heuristics into corresponding fuzzy heuristics is also demonstrated.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1098-1107 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fuel ethanol (95%) was produced from fodder beets in two farm-scale processes. In the first process, involving conventional submerged fermentation of the fodder beets in a mash, ethanol and a feed (PF) rich in protein, fat, and fiber were produced. Ethanol yields of 70 L/metric ton (7 gal/ton) were obtained; however, resulting beers had low ethanol concentrations [3-5% (v/v)]. The high viscosity of medium and low sugar, beet mashes caused mixing problems which prevented any further increase of beet sugar in the mash. The severely limited the maximum attainable ethanol concentration during fermentation, thereby making the beer costly to distill into fuel ethanol and the process energy inefficient. In order to achieve distillably worthwhile ethanol concentrations of 8-10% (v/v), we developed and tested a solid-phase fermentation process (continuous). In preliminary trials, this system produced fermented pulp with over 8% (v/v) ethanol corresponding to an ethanol yield of 87 L/metric ton (21 gal/ton). Production costs with this novel process are $0.47/L ($1.77/gal) and the energy balance is 2.11. These preliminary cost estimates indicate that fodder beets are potentially competitive with corn as an ethanol feedstock. Additional research, however, is warranted to more precisely refine individual costs, energy balances and the actual value of the PF.
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