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  • 1
    Electronic Resource
    Electronic Resource
    Electron microscopy of beaded agarose gels (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 201-212 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron microscopy has been carried out on sections of beaded agarose with a wide range of thicknesses, and the results have been analyzed by means of stereological theory using computer graphics. The results agree with a randomly orientated system in which, for 4% gels, the mean molecular weight per unit length of the fiber system is 110 kg mol-1 nm-1, and the number average interjunction length is 37 nm, with an asymmetrical distribution resembling a Maxwell-Boltzmann distribution. The spatial distribution of the structure is not uniformly random and there seem to be mi microvoids.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270204
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  • 2
    Electronic Resource
    Electronic Resource
    Degree of polymerization and polydispersity of xylan from the cell wall of the green seaweed Penicillus dumetosus (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1-9 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Xylan was extracted from the cell wall of green seaweed penicillus domutosus using a very mild procedure. Xylan dinitrate samples were prepared and their degrees of polymerization found to depend markedly on temperature, of nitration, the best compromise between yield and degradation being at about -20°C. Two samples, one obtained under optimum conditions and one highly degraded, were investigated in detail by using light-scattering, osmometry, gel-permeation chromatography, and viscosity techniques. The results show that there are xylan chains present, in the cell wall having degrees of polymerization above 10,000. This figure is much higher than those previously found for other similar xylans. The light-scattering results show that the xylan dinitrate molecule is much smaller than the molecules of the trinitrates of other structural polysaccharides (cellulose and mannan) for the same degree of polymerization. The effective bond length b is 16 Å, assuming a linear chain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360100102
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  • 3
    Electronic Resource
    Electronic Resource
    Solution properties of sodium alginate (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1839-1860 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sodium alginate fractions derived from three different sources - Laminaria hyperboria (75% guluronate), Fucus vesicularus (95% mannuronate), and Azotobacter vinelandii (85% mannuronate) - were investigated in aqueous solution over a wide range of ionic strength and pH using the techniques of light scattering, viscometry, and osmometry. Light-scattering data extrapolated to infinite ionic strength yielded b0 = 4.7 ± 0.3 and 3.0 ± 0.2 nm for the unperturbed effective bond lengths of the guluronate- and mannuronate-rich samples, respectively. These values are in the same ratio as predicted by conformational analysis, although lower by a factor of 0.7, probably due, in part at least, to the fact that measurements cannot be made on pure homopolymers. A comparison of the light-scattering and the viscosity data indicated that Φ in the Flory-Fox equation is lower than for more flexible polymers and increases with molecular weight, probably due to decreasing hydrodynamic permeability. Mark-Houwink exponents obtained from data extrapolated to infinite ionic strength were found to be considerably greater than 0.5, and we attribute this entirely to a variation in Φ. Comparison of the results obtained for the two mannuronate-rich samples indicated that the value of Φ and its variation with molecular weight can, in the case of alginates, differ markedly for chains, which, although having chemical differences, have similar chain statistics.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360191012
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  • 4
    Electronic Resource
    Electronic Resource
    An x-ray diffraction study of agarose gel as a function of concentration (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 1325-1328 
    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.360290820
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  • 5
    Electronic Resource
    Electronic Resource
    A laser light scattering study of gellan gels (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 371-382 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of gellan has been made using the technique of photon correlation spectroscopy. It has been confirmed that gellan gels are largely stationary at a molecular level like other polysaccharide gels and quite unlike the gels of flexible polymers such as polyacrylamide. Solution-gel transitions of deacetylated gellan in 0.025MNaCl have been studied both as a function of concentration and temperature, and the results compared with those of a parallel investigation of agarose. The interstitial spaces within gellan gels have also been studied by measuring the diffusion coefficients of dextran fractions within the gels. Since all gels are nonergodic systems, the theory of dynamic light scattering from such systems is discussed insofar as it affects the present work.It has been shown that the gellan and agarose aqueous systems are fundamentally different, in that agarose does not from a solution at very low concentrations, but splits up into macroscopic gel particles. At very low concentrations, gellan forms a solution in the presence of both gelleing and nongelling ions, the molecules of which shows little change in hydrodynamic diameter with temperature in the range 20-80°C.At higher concentrations where gels are formed, both gellan and agarose exhibit hystersis in their tempertature transitions from gel to solution and solution to gel, the solution being of large molecular aggregates. The transitions are sharp, but in both cases ther is a continous rearrangement in the structural morphology over the entire temperature range on heating, rendering the system more homogeneous prior to dissociation. In the case of gellan, however, there are two distincit phases in these structural changes - this is not true of agarose. The mean mass per unit length of the gellan fibre in the presence of 0.025M NaCl is 19 k daltons/nm at 0.7% concentration and varies with concentration to the power 0.15. The mass per unit length of the agarose fibre is much larger (ca. 110 k Daltons/nm), this difference being consistent with the difference in properties at very low concentrations. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360340309
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  • 6
    Electronic Resource
    Electronic Resource
    Laser light scattering study of polyacrylamide gels (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 699-716 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Laser light scattering experiments with polyacrylamide gels containing diffusing bovine plasma albumin are described. Complete heterodyne beating has not been assumed, and an account is given of a novel method for finding the degree of spectral broadening by scanning angles of scatter while measuring the temporal autocorrelation function. Results obtained by this method for polyacrylamide gels and un-cross-linked solutions in the absence of diffusing protein, are compared with those of other authors. In the presence of the protein there is a complex interaction between the diffusion coefficient of the protein and the coefficient associated with the diffusing fluctuations in segment density of polyacrylamide. The diffusing protein dominates at low gel concentrations, and the gel density fluctuations dominates at high gel concentrations. It is proposed that the protein preferentially occupies the less dense regions of the gel, so that at low gel concentrations, where it diffuses faster than the gel fluctuations, it tends to cancel them out, whereas at high gel concentrations where the protein is highly impeded by the gel structure, it tends to be carried along by the gel density fluctuations.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090250401
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  • 7
    Electronic Resource
    Electronic Resource
    The statistics of chain sectioning experiments on cellulose fibers (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1-7 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been suggested that transverse sectioning of natural cellulose fibers can be used to test ideas about microfibril structure. This proposal has been examined theoretically and numerical calculations of the weight-distribution curve of sectioned chains are given for several different models. These calculations illustrate the effects that different types of chain folding have on the sectioned size distribution. The difficulties involved in the practical execution of this type of experiment are discussed and it is concluded that fiber-sectioning experiments described in the literature do not disprove the folded-chain hypothesis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180130101
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  • 8
    Electronic Resource
    Electronic Resource
    A laser light-scattering study of the structure of agarose gels (1982)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 20 (1982), S. 659-679 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion coefficients of dextran fractions within agarose gels surrounded by dextran solution have been measured by laser light scattering using the autocorrelation method. Plots were made of the diffusion coefficient relative to that in dilute solution, D/D0, against the logarithm of hydrodynamic diameter logd for each concentration of agarose, and superimposed by displacing horizontally to produce a unified plot. In this way it was shown that D/D0 is a function of Cbd, where C is agarose concentration, with b = 1/3 and 1/2 for the cases in which the dextrans were mixed in before gelation and allowed to diffuse in afterwards, respectively, the plots being the same for a reference concentration of 0.7%. A value of b = 1/2 is that which would be expected if the molecular weight per unit length of the gel fibers were independent of concentration, and a value of 25 kg mol-1 nm-1 is calculated. Mobile concentrations of dextran within the gels relative to those in the surrounding solutions were found by determining the scattered intensity associated with the diffusing dextran molecules from the zero-time value of the autocorrelation function. All results and calculations are discussed in terms of current theories, and compared with earlier work on calcium alginate gels for which a molecular weight per unit length of gel fiber of 0.59 kg mol-1 nm-1 was calculated. The nature of the spectral broadening of the light scattered from agarose gels in the absence of dextran is described.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1982.180200409
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  • 9
    Electronic Resource
    Electronic Resource
    The sectioning of randomly branched filamentous structures (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 1367-1381 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theorectical analysis is given of the two-dimensional picture observed when a three-dimensional randomly branched fibrous structure is sectioned. The model adopted consists of randomly oriented, interconnected straight rods having either the same length or a defined distribution of lengths. Expressions are derived for the total number of fragments observed and their total apparant length per unit area projected in the plane of the section, together with the distribution function of the projectd lengths. However, the expression derived for the total projected length per unit area, one-fourth πtρl, where t is the section thickness and ρl the fiber length per unit volume in the three-dimensional stucture, is, however, independent of the above model. The theory is discussed in terms of electron microscopy which has been carried out by other workers on agarose gels.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.180220802
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