Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1965-1969  (4)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 4 (1966), S. 595-599 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The γ-benzyl-L-glutamate N-carboxyanhydride (NCA) polymerization initialed by diisopropylamine was studied in dimethylformamide (DMF)-dioxane mixtures of different compositions. It was found that the shape of the conversion versus time plots and the molecular weights of the polymers depend on the solvent composition. Auto-catalysis is present only when dioxane predominates in the solvent mixtures. Moreover, the molecular weight of the final polymer depends strongly on the precipitation conditions when the polymerization is carried out in DMF.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 963-971 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A block copolymer [γ-Et-DL-Glu]m [L-Trp]n was prepared using N-carboxy anhydrides (NCA) of L-tryptohan and γ-ethyl DL-glutamate. The block copolymer, dissolved in trifluoroethanol (TFE)-dichloroacetic acid (DCA) mixtures, exhibited a sharp change in the specific rotation at 546 mμ when the solvent composition reached 70-75% DCA content. Optical rotatory dispersion (ORD) and circular dichroism (CD) measurement were carried out in TFE solution in the spectral range 180-350 mμ. Indole side-chain chromophores were found to be optically active in the polymer. On the other hand, these groups exhibit very small optical activity in the model compound C6H3—CH2—O—CO—(L-Trp)2—O—CH3. Indole groups therefore appear to be in a dissymmetric environment only in the polymer. From these data it was concluded that poly-L-Trp is in some type of helical conformation in TFE. Strong overlapping of CD bands from side-chain chromophores and peptides chromophores in the wavelength range 185-240 mμ does not allow definite conclusions to be drawn about the type of helical conformation which exists in poly-L-Trp in TFE solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 1477-1486 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism (CD) measurements were carried out on various copolymers of L-tryptophan and γ-ethyl L-glutamate in ethylene glycol monomethyl ether as the solvent. On increasing the L-tryptophan content of the copolymers a gradual change in the CD spectra was observed. The typical spectrum of the right-handedα-helix becomes more and more evident as the L-tryptophan content decreases. On the basis of these results we assumed that no conformational transition occurs on proceeding from pure poly (γ-ethyl L-glutamate) to pure poly-L-tryptophan in ethylene glycol monomethyl ether: therefore the conformation of poly-L-tryptophan should be that of a right-handed α-helix. Moreover we observed that the change in the CD spectra of the copolymers is gradual but not linear on increasing the tryptophan content. The deviations from linearity were attributed to interactions among side-chain chromophores whose contributions to the optical activity are not simply additive. An x-ray analysis carried out on oriented films of poly-L-tryptophan casted from solutions of the polymer in dimethylformamide shows conclusively that the solid-state conformation of the polymer is that, of an α-helix.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 97 (1966), S. 113-127 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die SCHULZsche Theorie über die chromatographische Fraktionierung mittels BAKERWILLIAMS-Säulen wurde auf das System Poly-γ-benzyl-L-glutamat/Methanol/Methylenchlorid angewandt.Es wurde gefunden, daß die Trennung sehr wirksam ist, wenn die Fraktionierungsbedingungen sorgfältig ausgewählt werden. Darüber hinaus stimmen die Ergebnisse mit dem vermuteten Mechanismus der mit primären Aminen initiierten N-Carboxyanhydrid-(NCA)-Polymerisation gut überein. An den Ergebnissen der Fraktionierung wurde erkannt, daß das Zahlenmittel des Polymerisationsgrades P̄n annähernd dem Verhältnis der Monomeranfangskonzentration zur Initiatorkonzentration ([M]0/[I]0) gleich ist. Eine sehr große Uneinheitlichkeit wurde mit P̄w/P̄n ≃ 7 in Übereinstimmung mit älteren Literaturdaten gefunden1.
    Notes: The SCHULZ theory on the chromatographic fractionation with a BAKER and WILLIAMS column was applied to the system poly-γ-benzyl-L-glutamate/methanol/methylenechloride.It was found that the separation is very efficient if the fractionation conditions are carefully selected. Moreover the results are in good agreement with the suggested mechanism of N-carboxyanhydride (NCA) polymerization initiated by primary amines. In fact from the fractionation data it was found that the number average degree of polymerization P̄n is approximatively equal to the ratio between the initial concentrations of monomer and initiator ([M]0/[I]0). A very large inhomogeneity was found with P̄w/P̄n ≃ 7, in agreement with previous literature data1.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...