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  • Chemistry  (81)
  • Polymer and Materials Science  (32)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Enantioselective GC ; Permethyl-β-cyclodextrin ; Cyclopropyl amino acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0935-6304
    Keywords: Fluvalinate residues ; Honey ; Gas chromatography-atomic emission detection (GC-AED) ; Gas chromatography-mass spectrometry (GC-MS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two hyphenated techniques, gas chromatography-mass spectrometry and gas chromatography-atomic emission detection, have been used to identify the degradation products of the acaricide fluvalinate in a methanol solution of the commercially available formulation Mavrick, as well as in honey from beehives treated with this product. The major degradation products were 2-chloro-4-trifluoromethylaniline (I), methyl 2-[2-chloro-4-trifluoromethylaniline]-3-methylbutanoate (II), N-(2-chloro-4-trifluoromethyl-phenyl)valine (III), and 3-phenoxybenzaldehyde (IV). Fluvalinate in honey is gradually degraded, 3-phenoxybenzaldehyde being the most abundant residue.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 5 (1993), S. 738-741 
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 130-136 
    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
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 238-243 
    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
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1071-1076 
    ISSN: 0947-6539
    Keywords: fullerenes ; endohedral helium complexes ; NMR spectroscopy ; ring currents ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis- to hexakisadducts of C60 (1-6) and mono- to tetrakisadducts of C70 (7-13) containing 3He atoms (endo-hedral helium complexes) were prepared and studied by 3He NMR spectroscopy to determine the influence of degree of functionalization and addition pattern on the chemical shift of the 3He atom. In the series of C60 derivatives, which included the previously measured 6-6 monoadduct 3He@C61H2, the 3He resonance was shifted considerably upfield relative to that of 3He@C60 (δ = -6.36) up to the bisadduct 1 (δ = -11.45). The resonances of the higher adducts 3-6, however, were shifted only slightly further up-field and all appeared in a rather narrow spectral range between δ = -11.84 and -12.26. The absence of further substantial upfield shifts was rationalized in terms of the compensation of deshielding due to the functionalization-induced decrease in the diamagnetic π-electron ring currents that extend around the fullerene sphere by the shielding that results from the weaker pentagonal-ring paramagnetic currents and the increased number of localized benzenoid substructures in 3-6. In contrast, all 3He resonances of the C70 adducts are shifted downfield relative to the signal of 3He@C70 (δ = -28.81). A monotonic relationship exists between the chemical shift and the degree of functionalization, whereby the 3He chemical shifts steadily decrease from monoadduct 7 (δ = -27.53) to the isomeric tetrakisadducts 12 (δ = -21.09) and 13 (δ = -20.68). This deshielding was explained by the reduction of the strong diamagnetic ring currents extending along the polar corannulene perimeters as a result of the functionalization at α- and β-type polar bonds in 7-13. In both series, the addition pattern was also found to have a distinct influence on the 3He chemical shift.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0887-3585
    Keywords: peptide folding ; NMR ; CD ; 310-helix ; gp120 ; CD4 binding domain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A close association between the HIV surface protein gp120 and the CD4 T cell receptor initiates the viral multiplication cycle. A 15 amino acid peptide (LAV) within the CD4 binding domain of gp 120 has been shown to retain receptor binding ability. The structural behavior of the LAV peptide has been studied by CD and NMR methods in aqueous solution and upon addition of trifluoroethanol (TFE) to emulate the relatively apolar conditions at the membrane bound receptor. Previous work has shown that the LAV peptide folds into a β-pleated structure in more polar buffer/TFE mixtures, while a concerted structural change can be observed at a concentration of 60% TFE (v/v). This abrupt, cooperative refolding from a regular β-sheet to a helical secondary structure is known as “switch” behavior. Former CD experiments with LAV sequence variants have supported the assumption that four amino acids at the N-terminus (LPCR) are indispensable for the “switch.” The tetrad has a strong β-turn forming potential. The suggestion has been formulated that the tetrad can act as a nucleation site governing the refolding. The present NMR study of the LAV peptide in TFE gives evidence for a 310-helix suggesting that the tetrad adopts a type III β-turn and promotes the formation of a similar bend in the next overlapping tetrad until the sequence is restructured into a 310-helix at a critical polarity favoring intrachain hydrogen bonds. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 1012-1018 
    ISSN: 0749-1581
    Keywords: Peptide group proton shift effects ; Proton chemical shift computation ; Protein backbone conformation ; Solution peptide and protein structures ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been found that protein NH protons on top of a peptide group plane experience large upfield conformation shifts. The joint analysis of this effect and other known effects of the peptide group on proton chemical shifts has led to a two-term empirical expression for peptide group proton chemical shift computation as a function of protein backbone conformation. Both terms are expressed by McConnell's point-dipole shielding expressions, one referred to an axis perpendicular to the peptide plane and origin in the coordinate centre of the OCN atoms and the other referred to an axis along the carbonyl bond and origin close to the oxygen atom. Values for the two constants have been determined by least-squares fitting of the C-α, H and amide NH chemical shifts of the protein ubiquitin. As a cross-check on the validity of the expression, the C-α, H and NH shifts of ribonuclease and BPTI (basic pancreatic trypsin inhibitor) have been computed. The general agreement between the observed and computed shifts and the correlation coefficients found (0.72 on average) indicate that the expression accounts for the main physical effects of the protein peptide group on the proton chemical shifts. It is shown that, together with ring current shifts, the expression explains the main characteristics of the C-α, H and amide NH chemical shifts in proteins.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. S41 
    ISSN: 0749-1581
    Keywords: 1H NMR ; Two-dimensional NMR ; Azurin ; Nickel(II)-azurin ; Paramagnetic metalloproteins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H two-dimensional NMR experiments on nickel(II)-substituted azurin have been successfully applied. Despite the short relaxation times of the hyperfine-shifted resonances, the combined use of NOESY and COSY spectra allowed the assignment of 15 resonances belonging to the metal-coordinated residues Gly-45, His-46, His-117 and Met-121. Even in the case of the two broad and furthest downfield resonances, the NOESY spectra were successful in assigning these signals to the β-CH2 protons of Cys-112. The protons of the non-coordinated residues Met-13, Phe-15 and Trp-48 were also assigned via NOESY, COSY and TOCSY experiments.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 290-298 
    ISSN: 0749-1581
    Keywords: 2D NMR ; Mortonins A, C and D ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-field 2D NMR studies of mortonins were performed at 500 MHz (1H) and 125 MHz (13C). Unambiguous assignment both of the 13C data to the carbon skeleton and that of the proton chemical shifts in these molecules was achieved, together with the establishment of the configuration of the asymmetric centres. Some previously reported signals have been reassigned.
    Additional Material: 1 Ill.
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