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  • Polymer and Materials Science  (9,140)
  • 1980-1984  (9,140)
  • 1984  (3,071)
  • 1983  (3,022)
  • 1982  (3,047)
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  • 1980-1984  (9,140)
Year
  • 1984  (3,071)
  • 1983  (3,022)
  • 1982  (3,047)
  • 1981  (3,049)
  • 1980  (2,926)
  • 1
    Electronic Resource
    Electronic Resource
    Reduced sedimentation equilibrium time by two-step initial loading (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 17-24 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Computer simulation shows that the time required to attain near sedimentation equilbrium is dramatically reduced by a two-step initial loading in which a macromolecular solution at low or zero concentration is layered above one at a higher concentration. To achieve the minimum time requires a good estimate of the molecular weight, but at least a 50% reduction in time can be achieved if the molecular weight of the macromolecule is known only within a factor of 2. Numerical solutions to the differential equation of the ultracentrifuge are calculated using the finite element method. An efficient Gaussian elimination algorithm can be used to minimize calculation time and computer storage requirements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210103
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  • 2
    Electronic Resource
    Electronic Resource
    Fluorescent-labeled crosslinks in collagen: Pyrenebutyrylhydrazine (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 79-88 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aldehydes present in acid-soluble type I collagen react with pyrenebutyrylhydrazine to form various types of complexes under different reaction conditions. These complexes exhibit one or more of three different pyrene fluorescence bands: monomer, excimer, and aggregate fluorescence. Collagen, whose aldehydes have been reduced with NaBH4, does not react with this fluorescent hydrazine, confirming that the hydrazine reacts specifically with aldehyde groups to form hydrazones. The absence of a reaction with pepsin-treated collagen also shows that the fluorescent labels are primarily in the nonhelical terminal telopeptides. Upon dialysis, the pyrene label bound to a saturated aldehyde in an α-chain is lost; whereas that bound to an unsaturated aldehyde remains on the protein. The pyrene monomer fluorescence in the β-chain of old collagen is stronger than that of young collagen. The formation of the pyrene excimer fluorescence implies the proximity of two pyrene molecules, probably attached to two adjacent aldehydes. Upon changing from acidic to neutral pH, both excimer and aggregate fluorescence bands disappear within a few seconds, revealing a very rapid alteration at the telopeptides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210107
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  • 3
    Electronic Resource
    Electronic Resource
    A stereospecific complex of poly(I) with ammonium ion (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 147-157 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe conditions which lead to complete helix formation of poly(I) in the presence of NH4+. Binding of NH4+ is shown to be specific in the presence of Li+, which does not by itself support helix formation under these conditions. The NH4+-poly(I) complex is characterized by uv, CD, and ir spectroscopy. The CD spectrum is strikingly different from those of the Na+ or K+ complexes, the first extremum being changed from negative for the metal ions to positive for NH4+. A stereospecific model is proposed for the NH4+-poly(I) helix in which the N of NH4+ is located on the axis of the four-stranded helix, midway between planar tetramers formed by the bases. The model is consistent with the tetrahedral symmetry of NH4+, the requirement for four acceptable hydrogen bonds, the observed stability of the helix, and the accepted geometry of the backbone.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210112
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  • 4
    Electronic Resource
    Electronic Resource
    The δ-function counterion condensate around a line charge derived from the Fuoss, Katchalsky, and Lifson polyelectrolyte theory (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 159-167 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has recently been proven that the counterion condensate around an isolated line charge in an electrolyte, as characterized by nonlinear Poisson-Boltzmann theory, is an encapsulating δ-function. Here the identical result is shown to hold in the framework of the polyelectrolyte theory of Fuoss, Katchalsky, and Lifson. The proof fully exploits analytic solutions to the differential equation which are not available for the nonlinear, cylindrical Poisson-Boltzmann equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210113
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  • 5
    Electronic Resource
    Electronic Resource
    Interactions of DNA with divalent metal ions. II. Proton relaxation enhancement studies (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 203-218 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extent and modes of binding of the divalent metal ions Mn2+ and Co2+ to DNA and the effects of salt on the binding have been studied by measurements of the effects of these paramagnetic metal ions on the longitudinal and transverse relaxation rates of the protons of the solvent water molecules, a technique that is sensitive to overall binding. The number of water molecules coordinated to the DNA-bound Mn2+ and Co2+ is found to be between five and six, and the electron spin relaxation times and the electron-nuclear hyperfine constants associated with Mn2+ and Co2+ are little or not affected by the binding. These observations indicate little disturbance of the hydration sphere of Mn2+ and Co2+ upon binding to DNA. An average 2-3-fold reduction in the exchange rate of the water of hydration of the bound metal ions and an order-of-magnitude increase in their rotational correlation time are attributed to hydrogen-bond formation with the DNA. The binding constants of Mn2+ to DNA, at metal concentrations approaching zero, are found to be inversely proportional to the second power of the salt concentration, in agreement with the predictions of Manning's polyelectrolyte theory. A remarkable quantitative agreement with the polyelectrolyte theory is also obtained for the anticooperativity in the binding of Mn2+ to DNA, although the experimental results can be well accounted for by another simple electrostatic model. The various modes of binding of divalent metal ions to DNA are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210116
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  • 6
    Electronic Resource
    Electronic Resource
    Polyelectrolyte complexes of glycol chitosan with some polysaccharides. II. Electrical conductivity (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 265-275 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dc electrical conductivity of films of the polyelectrolyte complexes of glycol chitosan (GlChi) with the sodium salts of dextran sulfate (DS), carboxymethyl cellulose (CMC), polygalacturonic acid (GalUA)n, and alginic acid (AlgA) was measured at temperatures above and below room temperature. The maximum field strength in the thinnest film used amounted to 3 × 104 V/cm. A plot of normalized current against the reciprocal of the absolute temperature revealed two regions with different slopes, and activation energies in these two regions have been obtained for all the complexes. The activation energies in the high-temperature region vary from 0.85 to 1.18 eV and in the low-temperature region from 0 to 0.22 eV. Reasons are given to show that the conductivity is probably ionic. Near room temperature, the current-voltage relation is almost linear in the GlChi-DS complex, while in the other three complexes the current varies as a power n of the voltage with the value of n ranging from 1.7 to 2.5. A rise in temperatures causes an increase in the slope of the log I vs log V plot in GlChi-DS and GlChi-CMC complexes. The nonlinear current-voltage relation is ascribed to a space-charge-limited conductivity.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210203
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  • 7
    Electronic Resource
    Electronic Resource
    Crystallization behavior of glucomannan (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 301-319 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five different glucomannan samples were recrystallized from dilute solution. Depending on the experimental conditions, the crystals obtained could be identified as corresponding to the mannan I (anhydrous precipitate of more or less regular lozenge-shaped crystals) or mannan II (hydrated gel-forming pseudo-fibrillar precipitate). High-molecular-weight material, low temperature of crystallization, or a polar crystallization medium favored the mannan II polymorph, whereas a low-molecular weight, a high temperature of crystallization, and a crystallization medium of low polarity yielded the mannan I polymorph. Since the base-plane unit-cell dimensions are fairly constant with respect to variation of glucose, it is likely that isomorphous replacement of mannose by glucose occurs in glucomannan crystallization; the data also indicate that perfection of the glucomannan crystals was reduced in specimens having a high glucose:mannose ratio. The oriented crystallization of glucomannan on cellulose microfibrils was also studied under conditions where the mannan I polymorph was obtained. This gave shish-kebab structures that were characterized.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210206
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  • 8
    Electronic Resource
    Electronic Resource
    Thermodynamic functions of biopolymer hydration. I. Their determination by vapor pressure studies, discussed in an analysis of the primary hydration process (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 403-418 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary hydration process of native biopolymers is analyzed in a brief review of the literature, pertaining to various aspects of biopolymer-water systems. Based on this analysis, a hydration model is proposed that implies that the solution conformation of native biopolymers is stable at and above a critical degree of hydration (hp′ = 0.06-0.1 g H2O/g polymer). This water content corresponds to the fraction of strongly bound water, and amounts to ∼20% of the primary hydration sphere. In order to test this model, detailed sorption-desorption scanning experiments were performed on a globular protein (α-chymotrypsin). The results obtained are consistent with the proposed hydration model. They show that under certain experimental conditions, sorption isotherms can be obtained that do not exhibit hysteresis. These data represent equilibrium conditions and are thus accessible to thermodynamic treatment. Valid thermodynamic functions, pertinent to the interaction of water with biopolymers in their solution state, can be obtained from these sorption experiments.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210212
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  • 9
    Electronic Resource
    Electronic Resource
    Light scattering of bovine serum albumin solutions: Extension of the hard particle model to allow for electrostatic repulsion (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 451-458 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The light scattering of bovine serum albumin (BSA) has been measured at protein concentration up to 90 g/L and at pH values between 4.4 and 7.6. The dependence of scattering on both protein concentration and pH may be quantitatively accounted for by a simple extension of the hard-sphere model for protein solutions [Ross, P. D. & Minton, A. P. (1977) J. Mol. Biol. 112, 437-452] allowing for electrostatic repulsions between molecules. According to the extended model, the radius of the effective hard spherical particle representing BSA varies with the net electrical charge of the BSA molecule in a manner which may be calculated from electrostatic theory.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210215
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  • 10
    Electronic Resource
    Electronic Resource
    Comprehensive conformational analysis of (Gly-Pro-Pro)n and (Gly-Pro-Hyp)n related to collagen (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 475-497 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complete analysis of all possible conformations with correct hydrogen bonds of the collagen II type was performed on the basis of developed simultaneous equations. Using a unimodal search (by varying Ψ3), the energetically favorable structure was obtained. No other energetically satisfactory structural solutions are possible. The next aim was to obtain a precise model of the molecule. The program used includes a subroutine for continual deformation of the pyrrolidine rings. The set of parameters determining the structure consists of 14 independent variables (8 dihedral and 6 bond angles). As starting points for the energy optimization, conformations produced by scanning and some structures from previous work were used. The final structures (practically the same for both polymers) have helix parameters h = 0.285 nm and t = 52°, which are in excellent agreement with the 7/2 symmetry of diffraction data. The conformations of the pyrrolidine rings are of the B type, i.e., C2-Cβ-exo-Cγ-endo. For both polypeptides, the conformations of imino acids in position 3 of the triplet are the same; in position 2, however, they are slightly different. The difference in diffraction patterns for the 7/2 and 10/3 helices is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210302
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