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  • 1
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of isoleucinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-](C60H102N6O18) (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1517-1534 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analog of valinomycin, cyclo[-(D-Ile-Lac-Ile-D-Hyi)3-] (C60H102N6O18), has been determined by x-ray diffraction procedures. The crystals are orthorhombic, space group P212121, with cell parameters a = 11.516, b = 15.705, c = 39.310 Å, and Z = 4. The atomic coordinates for the C, N, O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation. Values of standard (R) and weighted (Rw) reliability factors after refinement are 0.073 and 0.056, respectively. The structure is completely asymmetric. The cyclic molecular backbone is stabilized by six intramolecular hydrogen bonds N—H…O=C, five bonds being of the 4→1 type and one being of the 5→1 type. The side chains are located on the molecular periphery. The conformational state of isoleucinomycin in the crystal is intermediate between the corresponding crystalline states of valinomycin and meso-valinomycin. The observed conformation suggests that complexation could proceed via entry of the ion at the face possessing the L-Lac residues, the less crowded face.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190808
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic and biochemical analysis of in vivo protein folding and subunit assembly (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 125-129 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The in vivo pathway of folding and subunit assembly of a trimeric bacteriophage protein has been studied by characterizing precursors to the native protein and by analyzing temperature-sensitive mutations that kinetically block the pathway. The native trimer is formed via an intermediate composed of three partially folded chains, the protrimer. At 39°C, temperature-sensitive mutations prevent the formation of both the native trimer and the protrimer, possibly by destabilizing earlier intermediates. However, the mutations do not affect the stability of the native protein, formed at 30°C. Thus, these mutations identify amino acid residues involved in interactions that determine the folding pathway.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220120
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  • 3
    Electronic Resource
    Electronic Resource
    Micellar Solubilization of Biopolymers in Hydrocarbon Solvents III. Empirical Definition of an Acidity Scale in Reverse Micelles (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2302-2311 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper deals with the problem of defining, and measuring, the pH inside the water pool (which we define as pHwp) of reverse micelles, i.e. micelles formed by surfactants dissolved in apolar solvents in the presence of minimal amounts of water. The conceptual and experimental difficulties are discussed, and it is argued that no absolute determination of pHwp is possible, mostly because water in the water pools of reverse micelles is a new solvent, for which no standardization of acidity is available. The problem can be approached only on the basis of an empirical acidity scale.An empirical acidity scale for water pools in reverse micelles of bis (2-ethyl-hexyl) sodium sulfosuccinate (AOT) in isooctane has been defined by measuring the 31P-chemical shifts of phosphate buffers. The chemical shifts in bulk water were compared to those found in reverse micelles under the assumption that the pK of phosphate ion is the same in the two systems. It was found that in most cases there was little difference (less than 0.4 pH units) between pHwp and the pH of the starting buffer in bulk water (which we define as pHst). However, this difference between pHwp and pHst may become much larger in certain cases.The difference (pHwp-pHst) is measured under a variety of conditions, and this permits the determination of an operational acidity in the micelle water pools as a function of the pHst with which the aqueous micelles are prepared. The significance of such data for interpreting the behaviour of enzymes confined in the micelles water pool is discussed. Based on the pHwp scale, the apparent pKa of phenol-red and 4-nitrophenol were determined in reverse micelles containing different buffers and different water content. The pKa values obtained were rather sensitive to changes of both these factors, which was taken to signify that organic dies have only a very limited applicability to measure the acidity of the water pools of reverse micelles.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630820
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  • 4
    Electronic Resource
    Electronic Resource
    Computer Assisted Structural Interpretation of Mass Spectral DataPart XXXVI of the series ‘Application of Artificial Intelligence for Chemical Inference’. For part XXXV see [1]. (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 458-470 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An interactive system of programs has been developed to assist in structure elucidation based on mass spectral data. The program relies on algorithms for generating all the structural isomers that constitute alternative explanations of the observed data and it associates relative plausibility values with the different isomers. The structure assembly part of the program allows for the use of overlapping substructural components, such as substructures inferred from the appearance of particular ion patterns in the spectrum of an unknown compound. Mass spectrum interpretation procedures used with this structure assembly process could exploit any form of spectrum-substructure correlation scheme. In this work, the emphasis has been on the use of detailed and class specific spectrum-substructure correlations. Applications of the program are illustrated by means of an example analysis of the mass spectra of a variety of marine sterols.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640210
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  • 5
    Electronic Resource
    Electronic Resource
    Computer-Assisted Structural Interpretation of 1H-NMR. Spectral DataPart XLI. Of the series ‘Application of Artificial Intelligence for Chemical Inference’. For Part XL. See [1] (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1898-1920 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interactive computer programs for the establishment and maintenance of a 1H-NMR. data base, the prediction of 1H-NMR. shifts and the rank-ordering of structural candidates based on comparison between observed and predicted spectra are presented. The programs take into account configuration, at stereocenters and double bonds, as well as diastereotopy. We demonstrate how, for purposes of structure elucidation, these new programs can be linked to the GENOA and STEREO programs.
    Additional Material: 13 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650624
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  • 6
    Electronic Resource
    Electronic Resource
    Studies in ring opening polymerisation, 6Part 5: cf.1.. Tertiary base initiated polymerisation of 5-phenyl-1,3-dioxolan-2,4-dione (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 313-324 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 5-Phenyl-1,3-dioxolan-2,4-dione (the anhydrocarboxylate derivative of mandelic acid) has been shown to undergo polymerisation in the presence of tertiary organic bases such as pyridine in a reaction that has somewhat unusual characteristics. Thus, although the reaction in nitrobenzene shows first-order kinetic dependence on both monomer and pyridine over a reasonable concentration range, the pyridine is not consumed and does not appear to control the molecular weight of the resultant polymer. The most important factor in controlling molecular weight is the presence of adventitious moisture which enters into the polymerisation process producing poly-α-esters that are hydroxyl/carboxyl terminated. The rate of polymerisation increases progressively as pyridine is replaced by 2-methylpyridine and 2,6-dimethylpyridine but decreases dramatically when 2-methoxypyridine is used, indicating the importance of the basicity of the attacking species. The results are interpreted in terms of the interaction of the basic nitrogen and the C-4 ring carbonyl leading to the formation of a transient charge transfer complex which subsequently decomposes to form pyridine, carbon dioxide and the α-lactone. The chain growth process involves the interaction of the α-lactone with any nucleophiles present which control the molecular weight and nature of the end groups.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820204
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  • 7
    Electronic Resource
    Electronic Resource
    Chemistry of naked persulfate, 3Part 2: cf.2.. Phase transfer free radical reactions: polymerization of acrylic monomers in organic solution using potassium peroxydisulfate in the presence of quaternary ammonium salts (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 701-703 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820243
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  • 8
    Electronic Resource
    Electronic Resource
    Metal acetylacetonates as latent accelerators for anhydridehyphen;cured epoxy resins (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 979-986 
    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: Twenty-two metal acetylacetonate compounds have been evaluated as possible latent accelerators for epoxy-anhydride solventless resins. Experimental data have revealed that titanium (IV) oxyacetylacetonate, chromium (III), zirconium (IV), cobalt (III), and cobalt (II) acetylacetonates are particularly effective with anhydride cured epoxy resins. When added to the resin at a level of 0.05-0.10% (w/w), they provide very fast gel times at 150-175°C combined with very good storage stabilities (〉 six months) at room temperature. The power factor values of cured resin samples, containing these preferred metal acetylacetonates, have been found to be between 2.0 and 2.5% at 150°C and 60 Hz. Correlation between the catalytic effectiveness of these metal acetylacetonates, as latent accelerators for epoxy-anhydride resins, and their thermal stabilities suggest that decomposition products may be the active species responsible for initiating polymerization in epoxyanhydride resin systems.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260320
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  • 9
    Electronic Resource
    Electronic Resource
    Equilibrium acid concentrations in hydrolyzed polyesters and polyester-polyurethane elastomersPresented in part at the 184th meeting of the American Chemical Society, Kansas City, MO, September 12-17, 1982, Ref. 1. (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 3779-3792 
    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: Equilibrium acid concentrations, [Ae], were determined in butylene adipate and caprolactone polyesters, of low molecular weight, and in thermoplastic polyurethane elastomers based on these polyesters. Values of [Ae] of the polyesters at 85°C were 0.7, 1.3, and 3-4 × 10-3 mol/g at relative humidities (RH) of 25%, 50%, and 93%, respectively. [Ae] of the thermoplastic elastomers at 85°C were about 3 and 7 × 10-4 mol/g at 10% and 25% RH, respectively. Values of [Ae] were not very dependent on temperature at constant RH. Equilibrated thermoplastic elastomers had low molecular weights and poor physical properties. Consequently, equilibration does not set a practical limit on hydrolytic degradation, even at low RH. Equations were developed that described the variation in acid content with time. Rate constants for hydrolysis and esterification increased as RH decreased. Reesterification in the elastomers in the absence of water is too slow to be a useful method of decreasing hydrolytic damage.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070281218
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  • 10
    Electronic Resource
    Electronic Resource
    Compatibility of poly(∊-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) blends. I. Blends containing SAN with 24 wt% acrylonitrile (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 1781-1795 
    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: Polymer blends of poly(∊-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN), containing 24 wt % acrylonitrile (AN), were prepared, and their transition behavior was examined by thermal analysis and dynamic mechanical testing. The blends were judged to be compatible on the basis of the presence of a single, compositionally dependent glass transition. The results of thermal treatment upon blends glass transition behavior and the dependence of thermal history upon the crystallization of semicrystalline PCL were also studied. The crystallization of PCL from SAN/PCL blends was found to be retarded by the presence of SAN, and crystalline PCL was found to exist only in blends containing a high PCL concentration. Blends which do not contain crystalline PCL were transparent, and their glass transition behavior can be correlated by the Gordon-Taylor equation. Phase separation, which was characterized by lower critical solution temperature (LCST) behavior, was found to occur when blends were heated to elevated temperatures.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290531
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