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  • 1
    Electronic Resource
    Electronic Resource
    The absence of an isotope effect on the stability of the poly-β-benzyl-L-aspartate α-helix in aprotic solvents (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 1745-1763 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optical rotatory dispersion measurements were used to follow the transition from the helical to the random coil conformation of poly-β-benzyl-L-aspartate as induced by changes in temperature and solvent composition in mixtures of dioxane and dimethylsulfoxide. Within experimental error, there is no difference in the stability of the helical state as measured in this way for the protonated and deuterated forms of the polypeptide. This result is considered in terms of previous attempts to study the isotope effect on conformational transitions of helical biological macromolecules and polypeptides. The conclusion is drawn that the apparent changes in conformational stability observed in these previous systems arise from alteration of the properties of the solvent. Speculations are advanced regarding the contribution of the interpeptide bond to the stability of the helical state.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110818
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  • 2
    Electronic Resource
    Electronic Resource
    Relative stability of the α-helix of deuterated poly(γ-benzyl-L-glutamate) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1939-1950 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coil-to-helix transition temperatures of hydrogen bearing and deuterated poly(γ-benzyl-L-glutamate) in 1,3-dichlorotetrafluoroacetone/H2O and/D2O mixtures, respectively, have been determined. Together with previously obtained data for the conformational transition of this polypeptide in normal and deuterated dichloroacetic acid, these results have been used in an analysis of the effect of deuterium substitution on the intrinsic stability of the α-helical form of poly(γ-benzyl-L-glutamate). The findings, consistent for both solvent systems, showed that the deuterated polypeptide is some 5% more stable than the normal protonated poly(γ-benzyl-L-glutamate), while the polypeptide-active solvent interaction enthalpy is also slightly increased by deuterium substitution in the respective molecules. A consideration of available data for poly(β-benzyl-L-aspartate) reveals an anomaly with respect to the present analysis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360151006
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  • 3
    Electronic Resource
    Electronic Resource
    Heat capacity increments: Conformational transitions in polypeptides (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 2411-2421 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermodynamic treatment of the helix-coil transition of synthetic polypeptides in binary organic solvent mixtures is extended to describe isobaric heat-capacity increments associated with the phenomenon. This development resolves such increments into three components: two associated respectively with intrinsic differences between the ordered and disordered states of the macromolecule and between the coil-solvent complex and its components, and a third term derived from the temperature dependence in the fraction of coil residues bound to active solvent. Insights derived from this analysis are also applied to the discussion of some heat capacity increments associated with the denaturation of globular proteins.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360221108
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  • 4
    Electronic Resource
    Electronic Resource
    Enthalpy changes in the helix-coil transition of poly(γ-benzyl L-glutamate) (1967)
    New York : Wiley-Blackwell
    Biopolymers 5 (1967), S. 27-35 
    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 temperature Tc of poly(γ-benzyl L-glutamate) in binary solvent mixtures of dichloroacetic acid and 1,4-dichlorobutane, 1-chlorooctane, or 1-chlorododecane have been measured. A treatment is presented with which the transition enthalpy can be calculated from the observed dependence of Tc on solvent composition. Results are compared with previously obtained calorimetric data. The underlying assumptions of the calculation are discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1967.360050105
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  • 5
    Electronic Resource
    Electronic Resource
    Deuteration and solvent composition effects in the helix-coil transition of poly-γ-beiizyl-L-glutamate (1966)
    New York : Wiley-Blackwell
    Biopolymers 4 (1966), S. 1015-1023 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of deuteration and of changes in solvent composition on the thermo dynamics of the helix-coil transition have been studied by calorimetric and optical measurements in the poly-γ-benzyl-L-glutamate-dichloroacetic acid-1,2-dichloro-ethanc system. For a given solvent composition, deuteration of the polypeptide and of the acid lowers the transition temperature Tc, while an increase in the volume fraction of acid in the solvent raises Tc. A rise in Tc is accompanied by a decrease in both the van't Hoff and the calorimetric heats of transition, but at different rates. The result is a temperature dependency in the Zimm-Bragg cooperation parameter σ. Possible causes of this result and its implications are discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1966.360040906
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  • 6
    Electronic Resource
    Electronic Resource
    Thermodynamics of the helix-coil transition in polypeptides in mixed organic solvents: The influence of inert solvent and side chain (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1823-1840 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced coil-helix transition of poly(γ-benzyl-L-glutamate) (PBLG) and poly(γ-methyl-L-glutamate) (PMLG) in binary solvent mixtures was investigated by calorimetric and optical rotatory dispersion (ORD) measurements. Dichloroacetic acid was the common active solvent, and the inert solvent was one of the chlorinated hydrocarbons, such as chloroform, 1,3-dichloropropane, 1-chlorobutane, or 1-chlorooctane.The thermodynamic parameters characterizing the intramolecular polypeptide and polypeptide-solvent interactions were calculated using the Karasz and Gajnos theoretical model [(1973) J. Phys. Chem. 77, 1139-1145]. It was found that the enthalpy (ΔH1) and entropy (ΔS1) of helix stabilization in the absence of the active solvent depend on the inert solvent, but only in the case of PBLG. This is explained by the additional helix stabilization achieved by the stacking of the benzyl groups. The stacking is more pronounced in less polar chlorinated hydrocarbons with longer aliphatic chains. The results obtained indicate that the maximum helix stability is reached in chlorinated hydrocarbons with 12 C atoms. In the case PMLG, with an aliphatic ester side group, ΔH1 and ΔS1 are independent of the inert solvent.The ORD measurements were used to determine the maximum fraction of helicity attained at constant solvent composition and the transition temperature, Tc, at the point where fH = 0.5. It was found that, for the same solvent composition, Tc was higher than the temperature of the midpoint of the calorimetric peak. This is explained by the fact that the maximum fraction of helicity is less than unity. The finite transition width was taken into account by calculating the phase boundaries for different fractions of helicity using the value of σ estimated from the calorimetric and van't Hoff enthalpies in the usual manner.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240912
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  • 7
    Electronic Resource
    Electronic Resource
    Compatibility of some fluorosubstituted styrene polymers and copolymers in blends with poly(2,6-dimethyl-1,4-phenylene oxide) and with polystyrene (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 219-224 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of poly(p-fluorostyrene) (PpFS), poly(o-fluorostyrene) (PoFS), poly(styrene-co-p-fluorostyrene) (SP46), poly(styrene-co-o-fluorostyrene) (SO49), with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and with polystyrene (PS), have been prepared by compression molding of coprecipitated polymers. Compatibility of these systems has been studied by differential scanning calorimetry. Detection of one or two glass transition regions was used to classify the blends as compatible or incompatible. Homopolymers of pFS and oFS were found to be incompatible with PPO and PS. The SP46 copolymer and SO49 copolymer were compatible with PPO in all proportions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070280119
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  • 8
    Electronic Resource
    Electronic Resource
    Carboxylation of poly(2,6-dimethyl-1,4-phenylene oxide) and thermal properties of blends with atactic polystyrene (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 2679-2682 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290823
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  • 9
    Electronic Resource
    Electronic Resource
    Poly(2-methoxyphenylene vinylene): Synthesis, electrical conductivity, and control of electronic properties (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 2867-2875 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(2-methoxyphenylene vinylene) has been synthesized by a four step reaction sequence beginning with the bromination of 2,5-dimethylanisole and proceeding to the formation of an intermediate sulfonium salt precursor polymer. The infrared and UV-visible spectra of the PPV derivative asymmetrically substituted on the phenyl ring are presented. Films of poly(2-methoxyphenylene vinylene) can be doped with iodine to give a conductivity of 1 S cm-1. Films doped with AsF5 exhibited activated charge transport behavior with room temperature conductivities of about 100 S cm-1.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281023
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation and electrical conductivity of poly(1,4-naphthalene vinylene)Dedicated to Prof. Dr. Georg Manecke on the occasion of his 70th birthday. (1986)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 24 (1986), S. 503-509 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1986.140241003
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