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  • Wiley-Blackwell  (30)
  • 1
    Electronic Resource
    Electronic Resource
    An improvement in the graphic treatment of angular light scattering data (1957)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 26 (1957), S. 305-310 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The well-known Zimm plot can be modified by plotting Kc/Rϑ sin2 (ϑ/2) against 1/sin2 (ϑ/2) with concentration c as a parameter, which gives a series of straight lines with a common intercept. By extrapolating to zero concentration one can determine the weight-average molecular weight from the reciprocal of the slope and the radius of gyration from the common intercept on the ordinate. This method finds applications for macromolecules having very high molecular weights.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1957.1202611405
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  • 2
    Electronic Resource
    Electronic Resource
    The non-newtonian viscosity of polymers in relation to their molecular conformation (1960)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 47 (1960), S. 333-348 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The non-Newtonian viscosities of polystyrene and polyisobutylene were measured in various solvents over a wide range of shearing stress, τ (up to the order of 104 dynes/cm.2). The shear dependence of the intrinsic viscosities, [η], is closely related to the molecular extension of the polymers. The non-Newtonian behavior of a polymer is greatest in a “good” solvent and least at Flory's Θ temperature. The maximum percentagewise drop in the intrinsic viscosities at highest attainable shearing stress was found to increase with increasing root-mean-square end-to-end distance, 〈r2〉1/2, of the polymer chains in “good” solvents. By plotting [η]τ = ∞/[η] τ = 0 against 〈r2〉1/2 / 〈rof2〉1/2(where 〈rof2〉1/2 is the theoretical 〈r2〉1/2 assuming free rotation about the chemical bonds of the polymer chains), the shear dependence of the intrinsic viscosities appeared to be absent when 〈r2〉1/2 / 〈rof2〉1/2 was extrapolated to unity. Furthermore, polymer having different degrees of chain stiffness seemed to form a composite curve in the plot, where the stiffer chains exhibited the most drastic drop in the intrinsic viscosities. Additional support was given with the experimental results of polydimethylsiloxane and cellulose triacetate solutions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1960.1204714930
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  • 3
    Electronic Resource
    Electronic Resource
    Polypeptides. VIII. Molecular configurations of poly-L-glutamic acid in water-dioxane solution (1957)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 23 (1957), S. 851-861 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The configuration of a poly-L-glutamic acid sample of 34,000 molecular weight has been studied in 0.2 M NaCl-dioxane (2:1) as a function of pH and temperature by intrinsic viscosity, optical rotation, optical rotatory dispersion and infrared spectroscopy. The intrinsic viscosity and specific rotation fall sharply in the pH range of 5.4-6.4 reaching values that remain constant at higher pH. The indications that these changes correspond to a reversible helix-random coil transition are substantiated by the demonstration that the optical rotatory dispersion shifts from the type characteristic of helices to the normal type as the pH is increased through the same region. Further evidence of the transition is found in infrared spectroscopic studies in solutions in which D2O has replaced H2O. The temperature dependence of the specific rotation and infrared spectra shows that within the pH region of 5.4 to 6.4 the equilibrium is shifted toward the coiled configuration by an increase in temperature. The analogy of this behavior with protein denaturation is obvious. It is noted that the transition from the helix to the coil does not begin until about 40% of the residues have become charged. The implications of the ability of the helical configuration to withstand this degree of electrostatic repulsion within its side groups is discussed in relation to the configuration of proteins.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1957.1202310429
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  • 4
    Electronic Resource
    Electronic Resource
    Conformation and aggregation of melittin: Effect of pH and concentration of sodium dodecyl sulfate (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1493-1504 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of melittin, a surface-active polypeptide, in solution was studied by CD spectra between 190 and 240 nm. The molecule was essentially unordered (possibly with a trace of helix) in water without salt at neutral pH. Upon deprotonation of four of the six cationic groups at pH 12 the polypeptide became partially helical (about 35%). The addition of NaDodSO4 to an aqueous melittin solution first caused the solution to become turbid but it became clear again in excess surfactant solution. The conformational changes depended on the molar NaDodSO4/melittin ratio, R. With R from 2.34 to 23.4, the melittin solution was turbid and the polypeptide conformation was probably a mixture of α-helix and β-sheets. This was supported by the ir spectrum of the turbid solution, which indicated the presence of both conformations. With R = 46.8 or 468 (1 or 10 mM NaDodSO4) the polypeptide conformation was characteristic of an α-helix, about 70-80% of the molecule, regardless of whether the surfactant was above or below its critical micelle concentration. This compared well with the x-ray results of 92% helix in crystals. The lower helicity of melittin in NaDodSO4 solution might be attributed to the end effects that destabilize the first and last turn of an helix at its N- and C-terminus, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250808
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  • 5
    Electronic Resource
    Electronic Resource
    Helical formation of a 13-residue C-peptide analogue of ribonuclease a in sodium dodecyl sulfate solution (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 423-430 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of a 13-residue C-peptide analogue of ribonuclease A -  - in surfactant solutions was studied by CD. The CD spectrum of the peptide in excess NaDodSO4 solution was typical for a helical conformation; the spectrum appeared to be virtually independent of pH (2.5-6) and temperature (3-25°C). Analysis of the CD data indicated a helicity of about 65-70% with no α-sheet and β-turn; this corresponded to 8 or 9 residues in the helical form or slightly more than two turns of α-helix. This compares with an average of about one turn of α-helix for the C-peptide analogue in water at pH 4.7 and 7°C. The conformation of the peptide in cationic surfactant, dodecyl ammonium chloride, and nonionic surfactant, dodecyl heptaoxyethylene ether, solution resembled that in water. We concluded that the C-peptide analogue can develop a maximum helicity close to the corresponding segment in ribonuclease A in hydrophobic environment provided by the clustering of NaDodSO4 molecules to the cationic side groups of the peptide, except that the end effects may destabilize two or three residues each at both ends of the helix. Thus, in the interior of a protein molecule this hydrophobic effect may overshadow the charged-group effect than can be explained by the helix dipole model for the helical segments on the exterior of the protein molecule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270306
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal unfolding of helices of a C-peptide analogue of ribonuclease A in sodium dodecyl sulfate solution (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 381-388 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of a 13-residue C-peptide analogue of ribonuclease A, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm suc - A}\mathop {\rm E}\limits^ - {\rm T - AAA}\mathop {\rm K}\limits^{\rm + } {\rm FL}\mathop {\rm R}\limits^{\rm + } {\rm A}\mathop {\rm H}\limits^{\rm + } {\rm A - CONH}_2 $\end{document}, in NaDodSo4 solutions with respect to temperature was studied with CD. The equilibrium constant of unfolding yielded a straight line in a van't Hoff plot. In 10 mM NaDodSo4, ΔGu = 120 cal/mol, ΔHu = 700 cal/mol, and ΔSu = 2.0 entropy units all on per helical residue. These values compared fairly well with the thermodynamic parameters of the uncharged helix-coil transition of (Glu)n in 0.1 M NaCl based on the theories of Zimm and Bragg and Zimm and Rice. The peptide was not unfolded at 75°C completely. Even in water without surfactant it was not a “random coil.”
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300315
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  • 7
    Electronic Resource
    Electronic Resource
    Conformation of poly(L-lysine) homologs in solutionTaken in part from a Ph.D. dissertation by Y.-W. T., University of California, San Francisco, 1975. (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 921-935 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the number of methylene groups in the side chains on the conformation of polypeptides is assessed for three poly(L-lysine) homologs with R = -(CH2)nNH2. Circular dichroism studies show a pH-induced helix-coil transition in 0.05 M KCl with midpoints at 9.6, 9.0, and 8.7 for n = 5, 6, and 7, respectively, as compared with 10.1 for (Lys)x (n = 4). Homologs with n = 6 and 7 could be partially helical even when the side groups are fully charged (with n = 7, the compound is highly aggregated above pH 9.1). Thus, the longer the number of methylene groups the more stable is the helical conformation of these homologs. Potentiometric titration of the n = 5 homolog gives a ΔG° of -310 cal/mol (residue) for the uncharged coil-to-helix transition at 25°C. The corresponding ΔH° and ΔS° are -1740 cal/mol (residue) and -4.8 e.u./mol (residue). Unlike (Lys)x, the uncharged helix-to-β transition is slow and incomplete even after heating at 80°C for 1 hr. Addition of methanol enhances the helical formation in neutral solution with midpoints at 72, 52, and 27% methanol (v/v) for n = 5, 6, and 7, respectively [cf. 88% for (Lys)x]. Addition of sodium dodecyl sulfate induces a coil-to-helix transition for all three homologs in contrast with the β form of (Lys)x under similar conditions.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160414
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  • 8
    Electronic Resource
    Electronic Resource
    Conformation of sequential and random copolypeptides of lysine and alanine in sodium dodecyl sulfate solution (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 2219-2236 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of sequential polypeptides, (Lysi-Alaj)n, and random copolypeptides, (Lysx, Alay)n, were synthesized. The competitive effect of Ala, a helix former, and Lys, whose homopolymer has a β-form in neutral NaDodSO4 solution, was determined by CD and absorption spectroscopy. All the polypeptides studied were unordered in neutral solution without the surfactant. Of the six sequential polypeptides only (Lys-Ala)n adopted a stable β-form in NaDodSO4 solution. Most striking is the difference between this polypeptide, (Lys2-Ala2)n and (Lysx, Alay)n, even though they all have equimolar Lys and Ala. (Lys2-Ala2)n was partially helical in 2.5-5 mM NaDodSO4 but approached the unordered form in 50 mM NaDodSO4, whereas (Lys50, Ala50)n was completely helical in all NaDodSO4 concentrations. Even Lysrich (Lys2-Ala)n and (Lys3-Ala)n formed a partial helix and a trace of the β-form, respectively, in low NaDodSO4 concentrations; both reverted to the unordered form in high NaDodSO4 concentrations. These results can be explained by Pauling-Corey's model for β-pleated sheets. Only (Lys-Ala)n has all DodSO4--bound Lys+ residues on one side and Ala residues on the other side of the polypeptide chain. They can nestle quiet efficiently in a β-sheet and between neighboring β-sheets. Our results further imply that random copolypeptides are not completely random; they comprise varying segments of (Lysk-Alam), where k and m could vary from zero to a small integer.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360221008
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  • 9
    Electronic Resource
    Electronic Resource
    Dilatometric and refractometric studies of the helix - coil transition of poly-L-glutamic acid in aqueous solutionThis work was supported by grants from the U. S. Public Health Service (GM-K3-3441, GM-10880, HE-06285). (1963)
    New York : Wiley-Blackwell
    Biopolymers 1 (1963), S. 359-370 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix - coil transition of poly-L-glutamic acid (PGA) in aqueous solutions was followed by volume changes, ΔV, and also differential refractive indices, Δn. The increase in ΔV or decrease in Δn upon mixing the sodium salt of PGA with dilute HCl gave three straight lines between pH 7 and 4, the two breaks corresponding to the transition zone observed by other physical methods. For the reaction: —COO- + H+ → —CO-OH, ΔV per mole of H+ bound was 11.4 and 11.1 ml. in 0.01 and 0.2M NaCl solutions, respectively. An additional conformational change of about 0.5-1 ml. per amino acid residue was observed for the reaction: coil → helix, after taking electrostatic interaction into consideration. This was probably due to the release of the water of hydration at the amide linkages when the polypeptide coil is converted into the α-helix, or even the occurrence of voids in the polypeptide chain as a result of imperfect packing of the atoms, although the origin of this volume change is still not fully understood at the present time. The volume changes as calculated from Δn by assuming a constant polarizability of the polymer was found to be higher for the association reaction than those mentioned above. On the other hand, the calculated ΔV for the transition was in fair agreement with those by direct measurements.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360010408
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction of sodium decyl sulfate with poly(L-ornithine) and poly(L-lysine) in aqueous solution (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 2263-2275 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding isotherms of sodium decyl sulfate to poly(L-ornithine), poly(D,L-ornithine), and poly(L-lysine) at neutral pH were determined potentiometrically. The nature of a highly cooperative binding in all three cases suggests a micelle-like clustering of the surfactant ions onto the polypeptide side groups. The hydrophobic interaction between the nonpolar groups overshadows the coulombic interaction between the charged groups. The titration curves can be interpreted well by the Zimm-Bragg theory. The average cluster size of bound surfactant ions is sufficiently large to promote the β-structure of (L-Lys)n even at a very low binding ratio of surfactant to polypeptide residue, whereas the onset of the helical structure for (L-Orn)n begins after about 7 surfactant ions are bound to two turns of the helix. The CD results are consistent with this explanation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360151113
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