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  • 1
    Electronic Resource
    Electronic Resource
    Vibrational analysis of peptides, polypeptides, and proteins. XXXII. α-Poly(L-glutamic acid) (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1479-1491 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Raman and ir spectra of α-helical poly(L-glutamic acid) have been assigned on the basis of a normal mode calculation for this structure. The force field was based on our previously refined main-chain force constants for α-poly(L-alanine) and side-chain force constants for β-calcium-poly(L-glutamate). Despite the identical backbone α-helical structures, significantly different frequencies are calculated, and observed, in the amide III and backbone stretch regions of α-poly(L-glutamic acid), as compared with α-poly(L-alanine). This clearly demonstrates the influence of side-chain structure on mainchain vibrational modes.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240805
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  • 2
    Electronic Resource
    Electronic Resource
    Raman and normal-mode studies of the extended-helix conformation in polypeptide chainsThis is paper number 36 in a series on vibrational analysis of peptides, polypeptides, and proteins, of which Ref. 23 is paper number 35. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. S99 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nature of the local main-chain conformation of polypeptides with charged side chains has been the subject of considerable discussion since Tiffany and Krimm first proposed [(1968) Biopolymers 6, 1379-1381] that, rather than being random, the chain is locally relatively regular, with conformations similar to that of a left-handed threefold helix. Such structures, referred to as “extended-helix” (EH) conformations, have now been studied in a charged poly(L-glutamic acid) system by a combination of Raman spectroscopy and normal-mode analysis. Calculations were done for EH conformations with 3.0 and 2.4 residues/turn, using force fields refined for α-helix, 31-helix, and β-sheet structures. Together with previous results on the α-helix and β-sheet forms, an interesting new correlation emerged: the frequency of the CαC stretch skeletal mode, usually found in the 900-1000 cm-1 region of the Raman spectrum, is essentially linearly correlated with the value of the φ angle. Applying this relationship to the observed frequencies of the α-helix and β-sheet forms of poly(L-glutamic acid), we find that an observed sharp band in the spectrum of crystals of the calcium salt of poly(L-glutamic acid) (which is close to the frequency observed for the charged form in solution) corresponds to an EH conformation very close to that predicted from energy calculations. These studies thus provide very strong support for our proposal that charged polypeptide chains are not random but adopt local conformations of the EH type.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260011
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  • 3
    Electronic Resource
    Electronic Resource
    7-Amino-actinomycin D complexes with deoxynucleotides as models for the binding of the drug to DNA (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 1749-1762 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorescence, CD, absorption, and 1H-nmr studies are reported for complexes of 7-amino-actinomycin D with deoxydinucleotides, deoxytetranucleotides, and poly(dG-dC)· poly(dG-dC). The optical spectra for the 7-amino-actinomycin D complex with pdG-dC, pdG-dC-dG-dC and pdC-dG-dC-dG are similar in shape to the 7-amino-actinomycin D complex with either DNA or poly(dG-dC). The changes in the 1H chemical shifts of the 7-amino-actinomycin D and the pdG-dC resonances that accompany complex formation show that 7-amino-actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The magnitudes of the induced chemical shifts for the 7-amino-actinomycin D complex formation with pdG-dC are similar to, but slightly different from, the induced chemical shifts which are obtained when actinomycin D forms a minature intercalated complex with two pdG-dC molecules. The pdN-dG dinucleotides (N = C, A, or T) form stacked complexes with 7-amino-actinomycin D. The presence of the 7-amino-group results in a larger dimerization constant (in aqueous solution) for 7-amino-actinomycin D [KD(6°C) = 4.4 × 103M-1], as compared to actinomycin D [KD(6°C) = 1.7 × 103M-1]; the chemical shifts which accompany dimer formation indicate that the chromophores stack in an inverted manner. Intercalation of 7-amino-actinomycin D into minature double helices, as well as into calf thymus DNA, poly(dG-dC)·poly(dG-dC), and poly(dA-dC)·poly(dG-dT), results in an enhancement of the relative fluorescence intensity and a shift in both the absorbance and corrected emission spectra.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360180712
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  • 4
    Electronic Resource
    Electronic Resource
    Über Pterinchemie. 62. Mitteilung. Protonenkatalysierte [1,2]-H-Verschiebung bei der Umlagerung von 6,7-Diphenyl-5,6-dihydropterin zu 6,7-Diphenyl-7,8-dihydropterin (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 922-924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton catalysed [1,2]-H-shift in the rearrangement of 6,7-diphenyl-5,6-dihydropterine (I) to 6,7-diphenyl-7,8-dihydropterine (III)The arrangement from I to the thermodynamically more stable III undergoes through a acid catalysed [1,2]-H-shift (intramolecular 6,7-hydride rearrangement) (see Scheme 1).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600322
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  • 5
    Electronic Resource
    Electronic Resource
    Über Pterinchemie. 73. Mitteilung [1]. Zum Verlauf der katalytischen Reduktion von 7-Methylpterin (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 395-401 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Pathway of the Catalytic Reduction of 7-MethylpterinThe catalytic hydrogenation of 7-methylpterin (VII) in a neutral solution occurs first by the reduction of the 7,8-double bond (thermodynamically-controlled reaction) followed by the reduction of the 5,6-double bond. On the contrary, in an acidic medium like CF3COOH, the 5,6-double bond is reduced first (kinetically-controlled reaction). The dihydro-intermediate then undergoes a [1,2]-H-rearrangement leading to the formation of the thermodynamically more stable 7-methyl-7,8-dihydropterin (XV) which on further reduction gives 7-methyl-5,6,7,8-tetrahydropterin (VIII). The catalytic reduction of 7-methyl-7,8-dihydropterin (XV) with deuterium gives stereoselectively a sole product with D at C(6) in the equatorial position.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630209
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  • 6
    Electronic Resource
    Electronic Resource
    Über Pterinchemie. 74. Mitteilung73. Mitt. s. [1].. Zum Verlauf der katalytischen Reduktion von 6-Methylpterin (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 1754-1758 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Pathway of the Catalytic Reduction of 6-MethylpterinThe catalytic hydrogenation of 6-methylpterin (I) in neutral or weekly acidic solution begins, as for the 7-methylpterin, by the thermodynamically controlled reduction of the 7,8-double bond. It is not possible to say, according to our experiments, which double bound, either the 5,6 or the 7,8, is first reduced in strongly acidic solution. However, a 5,8-reduction can be excluded.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630646
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  • 7
    Electronic Resource
    Electronic Resource
    Polymerisation of N-vinylcarbazole in pyridine using free radical initiators (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 1093-1099 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Vinylcarbazole (NVC) is polymerised in the presence of pyridine at 60°C by using azodiisobutyronitrile (AIBN) and benzoyl peroxide (Bz2O2) as initiators and the results are compared with those obtained when benzene is used as the solvent. In the AIBN-initiated system using pyridine as the solvent the rates of polymerisation follow an usual linear relationship with respect to monomer concentration and a square root dependence with respect to the initiator concentration. In the Bz2O2-initiated system, however, deviations from these ideal behaviours are observed when benzene and pyridine, respectively, are used as the solvent. Initiation occurs through the complexation of the monomer with Bz2O2 and degradative transfer is thought to be mainly responsible for this unusual kinetic behaviour.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830503
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  • 8
    Electronic Resource
    Electronic Resource
    Unified study of the mechanical and optical properties of polyoxymethylene applying the composite model for the temperature range from -60 to 120°C (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1017-1022 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A unified study of the optical and mechanical properties of polyoxymethylene (POM) is attempted in the framework of the composite model for a wide range of temperature (-60 to 120°C) which covers a region well below and above the γ-relaxation temperature. It was found that the existing two phase models for semicrystalline polymers are not adequate for interpreting the mechanical properties of POM over a wide temperature and drawing ratio range. The composite model takes into consideration the effects due to the change in crystallinity and orientation on drawing. The elastic moduli of the composite units are also calculated in terms of those of its constituents. The orientational changes on drawing were directly computed from the birefringence data. It was observed that the general agreement of the calculated and experimental values of the elastic moduli over the entire temperature and drawing ratio range is quite satisfactory.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870430
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  • 9
    Electronic Resource
    Electronic Resource
    Composite model calculation of the mechanical properties of polypropylene (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 1023-1034 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theoretical interpretation of the anisotropic elastic properties of polypropylene is given. It was found that none of the existing models provide a unified description of the mechanical and optical properties of ultradrawn polypropylene. The composite model proposed by the authors, which takes into account the change in orientation and crystallinity on drawing, was applied to investigate the elastic moduli data of polypropylene for a wide range of temperature (-40 to 110°C) and over the entire drawing ratio range. The relationship between θ and θ′, the angles made by the C-axis of the composite unit with drawing direction, was found to be adequately described by the relation tan θ = φ(n) tan θ′. It was further observed that φ(n) in the above relation obtained from birefringence data predicts the correct orientational changes on drawing for the temperature range -40 to 24°C. This makes the evaluation of mechanical properties possible without introducing any arbitrary parameter. However, it is noticed that a particular analytical form of φ(n) with two parameters is quite successful in interpreting the mechanical properties data over the entire temperature range. The abrupt changes of the parameters at certain temperatures seem to be correlated with the β-relaxation and glass transition temperature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870431
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  • 10
    Electronic Resource
    Electronic Resource
    A composite model for the thermal conductivity of semicrystalline polymers (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 217-226 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A phenomenological model is proposed which considers the polymer as an aggregate of units. The units are composed of two distinct phases  -  amorphous and crystalline. The thermal conductivity of a unit is calculated in terms of those of its constituents. In the undrawn state these units are distributed randomly, and the isotropic thermal conductivity of the bulk results. The development of strong anisotropy in thermal conductivity is explained in terms of the preferred orientation of these units. The structural features of this model are similar to those employed for the interpretation of the mechanical properties. The change in orientation of the units was deduced from the experimental data of birefringence. Finally, the results obtained from the composite model for several semicrystalline polymers are compared with the experimental data and other existing calculations. The model is found to give a fair overall description of the thermal conductivity in the cases of polypropylene, polyoxymethylene, low and high density polyethylene, and polychlorotrifluoroethylene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880118
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