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  • Polymer and Materials Science  (19)
  • Physics  (5)
  • 1975-1979  (19)
  • 1970-1974
  • 1965-1969
  • 1975  (19)
  • 1
    Electronic Resource
    Electronic Resource
    New structures of LD-alternating polypeptides in solution and in the solid state (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1109-1114 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140518
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of sequential polypeptides containing L-azetidine-2-carboxylic acid residues (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2211-2230 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of a series of sequential polypeptides with the repeating sequences Aze-Pro-Aze, Pro-Aze-Pro, Pro-Aze-Gly, Aze-Pro-Gly, Ala-Aze-Gly, Aze-Ala-Gly, and Pro-Pro-Gly are reported. The polymers were prepared by the active ester method, using the p-nitrophenyl, pentachlorophenyl, and N-hydroxysuccinimide esters as the polymerizable tripeptide derivatives. Except for poly(Ala-Aze-Gly) obtained via the N-hydroxysuccinimide ester, all polymers were isolated in good yields and have weight-average molecular weights in the range 10,000-30,000. The molecular weights have been determined by applying the calibrated gel chromatography system described by Fairweather et al. [J. Chromatogr. (1972) 67, 157] and by viscometry. All di- and tripeptide intermediates were chemically and optically pure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360141016
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  • 3
    Electronic Resource
    Electronic Resource
    On the application of polyelectrolyte limiting laws to the helix-coil transition of DNA. III. Dependence of helix stability on excess univalent salt and on polynucleotide phosphate concentration for variable equivalent ratios of divalent metal ion to phosphate (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1407-1422 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the free energy difference between double-helix and random-coil forms of DNA as a measure of the stability of the double helix, we calculate the dependence of the stability on excess univalent cation concentration and on polynucleotide phosphate concentration, both as functions of the equivalent ratio r of divalent cation-to-phosphate concentrations. The theoretical tool is merely to compare the free energy of one polyelectrolyte solution, characterized by the polyelectrolyte linear charge density, with the free energy of another, characterized by a different value of the charge density. It is assumed only that the charge density of the double helix is greater than that of the coil form. The calculation represents the only molecular theory given to date (for r ≠ O) for these aspects of helix stability.We find that, as excess univalent cation concentration increases, the helix stability increases if r is small but decreases if r is large (i.e., of the order of unity). Moreover, as the concentration of nucleotide phosphate increases, the helix stability does not change for small values of r but increases for large values. For both effects, a continuous transition as a function of r bridges the low-r and high-r behaviour.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140708
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational analysis of polynucleotide chains. Double-stranded structures (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1667-1684 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational analysis of double-stranded helical polynucleotides was carried out in terms of internal and external parameters, using semiempirical energy potential functions. The results obtained show that the structures proposed on the basis of the X-ray analysis for A-DNA and RNA's are almost identical to those corresponding to the conformational energy minima, whereas that proposed for B-DNA still appears to suffer from conformational strains. On the other hand, the B-DNA structure theoretically predicted is stabilized by both van der Waals energy and possible specific interactions with water molecules and counterions. This may explain the stability of the B form with respect to the A form at high relative humidity and ion strength. A possible role of the A + T fraction in stabilizing the B-type DNA emerges in connection with its preferential ability to bind ions. This agrees with the results on the crystalline structures of GpC and ApU. For RNA's, the occurrence of only A-type structures is explained as being due to the C(3′)-endo puckering of ribose in a double helix.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140810
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  • 5
    Electronic Resource
    Electronic Resource
    Transient electric birefringence of sonicated DNA (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2441-2443 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360141119
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of long-chain branching distribution in polyethylene by combination of gel permeation chromatography and viscometry (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 203-212 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die direkte Messung der Grenzviskositätszahl von Fraktionen aus der Gelpermeations-chromatographie wird mit dem Konzept der universalen Eichung kombiniert, um Langkettenverzweigung in Polyáthylen zu bestimmen. Das experimentelle Verfahren, einschließlich einer Diffusionsverbreiterungskorrektion für das begrenzte Auflösungsvermögen unseres chromatographischen Systems, wird beschrieben. Die Ergebnisse für drei verzweigte Polyäthylene werden mit den Ergebnissen verglichen, welche mit der Standardmethode (Präparative Kolonnenfraktionierung und Untersuchung der Fraktionen mit Lichtstreuung und Viskosimetrie) erhalten werden.
    Notes: Direct measurement of intrinsic viscosity on gel permeation chromatography effluent was combined with use of the universal calibration concept in order to determine long-chain branching in polyethylene. The experimental procedure, involving an axial dispersion correction for the limited resolution of our chromatographic system, is presented. Results obtained for three branched polyethylene samples are compared with those provided by the well-established method of preparative fractionation by column elution and examination of the fractions by viscometry and light scattering.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760115
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of oxidative polymerization of 1,8-nonadiyne (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 1369-1381 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß der Katalysator-, Monomer-, Liganden-, Wasser- und Sauerstoff-Konzentration auf die Kinetik der oxidativen Polymerisation von 1,8-Nonadiin (1) bei 26°C wurde untersucht. Die Oxidation wurde ausgeführt in Anwesenheit eines homogenen Katalysators aus einem tertiären Amin und Kupfer(I)-chlorid. Die Reaktion ist anfangs fast erster Ordnung bezogen auf [Cu2Cl2] bis zur Löslichkeitsgrenze des aktiven Katalysators und zweiter bis erster Ordnung bezogen auf [1] für kleine bis mittlere Monomer-Konzentrationen. Die Reaktionsgeschwindigkeit nimmt mit zunehmendem Wasser-Gehalt ab und steigt mit zunehmender Konzentration und zunehmender Basizität des Liganden: Triäthylamin (TEA) 〉 N,N,N',N'-Tetramethyläthylendiamin (TMED) 〉 Pyridin. Aufgrund dieser kinetischen Ergebnisse und einer Untersuchung der Katalysator-Struktur wird ein Reaktionsschema vorgeschlagen. In diesem Schema wird in einem reversiblen Reaktionsschritt Wasser aus acetylenischen Endgruppen und einem dimeren Kupfer(II)-Komplex [TMED.Cu(OH)]22 · 2Cl- gebildet. Danach findet eine intramolekulare oxidative Kupplung von zwei komplexierten Acetylid-Ionen statt.
    Notes: A study was made of the influence of the concentrations of catalyst, monomer, water, ligand, and oxygen on the rate of oxidative polymerization of 1,8-nonadiyne (1) at 26°C in the presence of homogeneous catalysts derived from cuprous chloride (copper(I) chloride) and tertiary amines. In the initial stages the reaction is nearly first order in [Cu2Cl2] up to the solubility limit of the active catalyst, and second to first order in [1] for low to medium monomer concentrations. The reaction rate decreases with increasing water content and is enhanced by increasing ligand concentration and increasing basicity of the ligand: triethylamine (TEA) 〉 N,N,N',N'-tetramethylethylenediamine (TMED) 〉 pyridine. On the basis of these kinetic results and a study of the catalyst structure a reaction scheme is proposed. In this scheme the formation of water occurs in reversible reaction steps from acetylenic endgroups and a dimeric copper(II) complex [TMED. Cu(OH)] · 2Cl-, followed by intramolecular oxidative coupling of two complexed acetylide ions.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760512
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanism of the radiolysis of poly(methyl methacrylate) at 77K effect of ethanethiol on post-irradiation reactions (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 3493-3496 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021761130
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular weight distribution of native poly(D-β-hydroxybutyric acid) (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 2655-2667 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Molekulargewichtsverteilung des Biopolyesters 1 aus D-β-Hydroxybuttersäure untersucht, der unter Erhaltung seiner nativen molekularen Eigenschaften aus Rhizobium meliloti isoliert worden war. Das Gewichtsmittel des Polymerisationsgrads liegt bei DPW=23000, weswegen man 1 als eines der höchstmolekularen Biopolymere ansehen kann. Die Kettenlängenverteilung von 1 weist auch noch nach 30 Stunden Synthesezeit eine außerordentlich große Einheitlichkeit auf. Daraus läßt sich schließen, daß auch endogene bakterielle Polymere wie 1 nach einem Mechanismus synthetisiert werden, der einheitliche Moleküle erzeugt. Dies kann ein Poisson-Mechanismus sein, bei dem die mittlere Synthesezeit in etwa mit der mittleren Generationszeit der Bakterien übereinstimmt.
    Notes: The molecular weight distribution of the biopolyester 1 from D-β-hydroxybutyric acid, isolated from Rhizobium meliloti by methods which preserved its native molecular properties, was studied. The weight average degree of polymerization is approximately DPw=23000, 1 being therefore one of the highest biopolymers with respect to chain length. The distribution of the degree of polymerization of 1 is distinguished by a great homogeneity, which it still possesses even after 30 hours of synthesis. One can conclude, therefore, that biosynthesis of an endogeneous bacterial polymer like 1 takes place also by a mechanism which produces molecules of homogeneous chain length, as e.g. a Possion type mechanism, and where the mean time of synthesis coincides approximately with the mean time of generation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760915
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  • 10
    Electronic Resource
    Electronic Resource
    Liquid crystalline acrylates and their polymers bulk and solution polymerization of 5β-cholestan-3-yl methacrylate (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 495-499 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760219
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