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  • Polymer and Materials Science  (34)
  • Physics  (6)
  • 1975-1979  (34)
  • 1970-1974
  • 1965-1969
  • 1976  (15)
  • 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
    Modern methods for the analysis of urea formaldehyde resins (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 54 (1976), S. 187-201 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Moderne instrumentelle Methoden wurden zur Analyse von Harnstoff-Formaldehyd-Harzen verwendet. Ein ausführliches Studium der Silylierung des Harzes mittels BSTFA (N,O-Bistrimethylsilyltrifluoracetamid) ermöglicht die quantitative gaschromatographische Bestimmung der niedermolekularen Verbindungen Harnstoff, Monomethylolharnstoff und Dimethylolharnstoff. Das Verhältnis zwischen nieder- und hochmolekularen Verbindungen sowie die Mengen an niedermolekularen Verbindungen können mittels GPC-Analyse auf Sephadex LH 20 in Wasser ermittelt werden.Ein vollständiges Bild des Harzes erhält man durch 220 MHz 1H-NMR-Analyse von Lösungen von gefriergetrockneten Proben in DMSO-d6. Zusammen mit den Ergebnissen klassischer chemischer Analysen ergeben die Resultate der drei genannten Techniken einen guten Überblick über den Aufbau eines Harnstoff-Formaldehyd-Harzes.
    Notes: Modern instrumental techniques were used for analysing water-based urea-formaldehyde resins. An exhaustive study was made of the silylation of such a resin with BSTFA (N,O-bistrimethylsilyltrifluoroacetamide). From the gas chromatograms the amounts of urea, monomethylol urea and dimethylol urea can be determined quantitatively, thus giving information on the low molecular weight part of the resin. The ratio of low to high molecular weight components as well as the amounts of several low molecular weight compounds can be estimated from a GPC analysis on Sephadex LH 20 in water. A detailed picture of the resin is obtained when freeze-dried samples are subjected to 220 MHz 1H-NMR analysis in DMSO-d6.An overall insight into the composition of these resins can be gained when the results of the mentioned techniques are combined with those of classical chemical analyses.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1976.050540114
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    On the application of polyelectrolyte limiting laws to the helix-coil transition of DNA. IV. Dependence of helix stability on the concentration of divalent metal ions (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 457-468 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular theory of the previous paper in this series is extended to determine the effect of divalent metal ions on helix stability relative to coil at fixed ionic strength and nucleotide phosphate concentration. Specification of the state of condensed counterions, as well as their concentration, is essential for the solution of this problem, and it is assumed that they translate freely within a thin cylindrical shell close to the polynucleotide. As a function of divalent counterion concentration mB2+ the relative stability of the helix is highly nonlinear. Although the overall trend is that the helix stability increases with addition of divalent metal ion, there is a narrow concentration range for which it decreases slightly. The behavior of the relative stability as a function of mB2+ is determined by the translational degrees of freedom of the counterions, both univalent and divalent, both condensed and uncondensed. Detailed comparison of the theory with data is not given here, but it is pointed out that the calculated values of the relative stability are consistent with the order of magnitude of the observed effect Mg2+ on the melting temperature.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150303
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  • 5
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    An easy method for retrieving atomic coordinates from CPK space-filling molecular models (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1825-1833 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Connectors for CPK space-filling molecular models have been supplemented with pointed steel wires (φ = 1.59 mm) of appropriate lengths and positions to represent atomic bonds. For illustration purposes, the polypeptide backbone of glucagon was equipped with such wire-core connectors and given a possible conformation. The molecular model was packed into a cubic box and, using a clinical instrument, X-ray films were taken from three orthogonal directions. Atomic coordinates on the films were then corrected to real-space coordinates.This method for retrieving atomic coordinates from space-filling models of modium-sized polypeptides is easy and can be done wih equipement available everywhere. Coordinates obtained in this way should be useful as starting points for energy minimization, for the calculation of frictional coefficients, and in attempts to solve crystal structures by X-ray diffraction, using molecular replacement methodology.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150915
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  • 8
    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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  • 9
    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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  • 10
    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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