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  • 1
    Electronic Resource
    Electronic Resource
    The dynamics of the helix-coil transition in poly-α, L-glutamic acidAn account of this work formed part of a paper delivered at the Fifth International Congress of Biochemistry, Moscow, 1961. (1964)
    New York : Wiley-Blackwell
    Biopolymers 2 (1964), S. 489-500 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Temperature jump measurements employing optical rotation to follow transients show an upper limit of 10μsec. on the half time of the helix-random coil relaxation in poly-α, L-glutamic acid. No relaxations are observed under conditions where the polymer exists in completely helical or completely random coil form. Assuming that the helix-coil transition can be described kinetically as a pure growth process, expressions for the relaxation time are derived for three special cases. A comparison is made between the rate of the helix-coil transition and the rate of imide proton exchange.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1964.360020507
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  • 2
    Electronic Resource
    Electronic Resource
    Electrostatic interactions in polyglutamic acid (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 845-856 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy estimates were made for completely charged polyglutamic acid with different assumptions concerning the placement of side chain charge. Viewed as a helix, the minimum energy structure is somewhat affected by the side-chain charge placement. The average energy of the chain viewed as a random coil is equal to or less than the average energy of the chain viewed as a helix. Unlike the polyacrylate chain, nearest-neighbor charge interaction is shown to increase the chain dimensions. Although the calculations are approximate there is little evidence to suggest that isolated polyglutamate molecules in the absence of added electrolyte should behave as rods or that there are significant amounts of locally ordered structures. Presently no experimental results exist under conditions appropriate to isolated molecular calculations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120413
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of residual side chain blocking groups and side chain charge on polypeptide conformation in aqueous solution (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 835-843 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD) spectrum of poly-L-lysine and poly-L-glutamic acid has been investigated in the presence of a small percent of side-chain blocking groups. The blocking groups benzyl, methyl, and carbobenzoxy show qualitatively similar effects. Less than five mole percent of aromatic blocking groups alters the CD spectrum. Consequently, unsuspected blocking groups may account for the variation observed in CD spectra of these polymers. A weak CD band at 235-240 nm was observed for the disordered unblocked polymer even in the absence of electrolyte. Viscosity data indicate that in salt-free solutions these chains at neutral pH still behave as random coils though with reduced conformational freedom, in contrast to some polyelectrolytes which behave as rigid rods in the absence of electrolyte. The viscosity data bring into question the relevance of isolated molecule conformational calculations to experimental CD spectra.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120412
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  • 4
    Electronic Resource
    Electronic Resource
    Thermodynamic parameters of the helix-coil transition in polypeptide chains. III. Random copolymers of L-leucine with L-glutamic acidThe preceding two papers of this series are Refs. 1 and 2. (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1739-1753 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational transitions induced by pH changes in random copolymers of leucine and glutamic acid have been studied. Significant differences were observed in the potentiometric titration curves of copolymers with small (up to 4%) and large leucine contents. The helical stability of copolymers with small leucine content, determined from titration curves by the Zimm and Rice method, decreases slightly with an increase in the leucine content, whereas the helical stability of copolymers with large leucine content increases sharply with an increase of the leucine content. It is shown that copolymers with large leucine content aggregate in the region of transition into the helical state, but the increase of their helical state stability is not connected with intermolecular aggregation, as it was also observed for a nonaggregating fraction isolated from one of the copolymers by gel chromatography. A conclusion is made that the helix-coil equilibrium constant s for leucine does not itself exceed the s constant for uncharged polyglutamic acid. The stabilization of the helical state in copolymers with large leucine content is due to intramolecular aggregation of helices in these copolymers. The analysis of the leucine residue distribution between helical and nonhelical regions in globular proteins also gives no real arguments to ascribe special helix-forming properties to leucine.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140814
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