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  • 1
    Electronic Resource
    Electronic Resource
    Unsaturated amino-acid residues as probes for the conformation of polypeptides in solution (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1677-1686 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetyl-(dehydro-Phe) and acetyl-bis(dehydro-Phe) groups have been attached to the ε-amino group of the lysine residues of the copolymer poly(Glu92Lys8) by reacting this last with acetyl-(dehydro-Phe)-azlactone and acetyl-bis(dehydro-Phe)-azlactone, respectively.In the latter case induced CD is observed between 250 and 330 nm, due to the relative dissymmetric disposition of the two dehydro-Phe groups under the chiral field of the polypeptide chain.pH dependence of the induced CD, observed for the copolymer and lacking in the lowmolecular-weight structural model, is related to the α-helical and random coiled conformation of the polypeptide chain.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160806
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  • 2
    Electronic Resource
    Electronic Resource
    Solution structure of peptides containing two dehydro-phenylalanine residues: A CD investigation (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1-10 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The peptides Ac-ΔPhe-Ala-ΔPhe-NH—Me (1), Ac-ΔPhe-Val-ΔPhe-NH—Me (2), Ac-ΔPhe-Gly-ΔPhe-Ala-OMe (3), and Boc-Ala-ΔtPhe-Gly-ΔPhe-Ala-OMe (4), containing two dehydro-phenylalanine (ΔPhe) residues, were synthesized and the solution structure investigated in various solvents. The nmr and CD measurements indicate that all the dehydropeptides examined adopt 310-helical conformations in solution. The tripeptides 1 and 2 exibited an intense negative CD exciton couplet, which was assigned to the right-handed screw sense, while the tetrapeptide 3 displayed a CD couplet having opposite sign, which was assigned to the left-handed helical sense. In the pentapeptide 4 the sense of the helix was found to vary with solvent and temperature, as demonstrated by the sign reversal of the CD spectrum. The right-handed sense dominates in hexafluoro-2-propanol, whereas a left-handed helix prevails in chloroform, acetonitrile and methanol. A crucial role for this behavior is likely to be played by the two alanine residues positioned respectively at the head and tail of the sequence, which favor conformations having opposite screw senses. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330102
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  • 3
    Electronic Resource
    Electronic Resource
    Azobenzene-Containing polypeptides: Photoregulation of conformation in solution (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1423-1437 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochromic polypeptides, with 16 to 56% azobenzene groups in the side chains, have been prepared by reaction of poly(L-glutamic acid) with p-aminozaobenzene, both in the presence of dicyclohexyl carbodiimide/N-hydroxybenzotriazole and of pivaloyl chloride. Analogous modification reactions carried out on poly(L-aspartic acid) were unsuccessful owing to the formation of N-succinimide rings. In trimethylphosphate, all the azopolypeptides exhibit the α-helix CD pattern. Irradiation produces the trans-to-cis isomerization of the azo side chains, but does not induce any variations of the backbone conformation. In water, the CD spectra indicate the presence of appreciable amounts of α helix in 16 and 21% mol azo-containing poly-(Lglutamates), while a β structure is present in a 36% mol azopolypeptide. Light produces conformational changes of the polypeptide conformation which are completely reversed in the dark. The extent and kind of photobehavior depend on the azo content and the pH value at which irradiation is carried out. The light-induced effects are discussed on the basis of the pH-induced order-disorder conformational transitions. In fact, the pK values and the transition curves of the dark-adapted samples were found to be different from those of the irradiated ones.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230723
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  • 4
    Electronic Resource
    Electronic Resource
    Optically active hydrocarbon polymers with aromatic side chains, 5Part 4: cf.10, preceding paper, page 15.. Conformational and chiroptical properties of stereoregular polymers of phenyl-α-olefins (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 174 (1973), S. 27-37 
    Details
    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 chirooptischen Eigenschaften von stereoregulären Polymeren aus optisch aktivem 4-Phenyl-1-hexen (1) und 5-Phenyl-1-hepten (2) sowie von Copolymeren aus 1 und 4-Methyl-1-penten (3) wurden untersucht. Der Vergleich des Drehwerts sowie der CD-Spektren im Bereich der π→π*-Absorptionsbanden des aromatischen Chromophors dieser Polymeren mit den entsprechenden Eigenschaften der optisch aktiven Phenylalkane erlaubt den Schluß, daß die Makromoleküle von Homopolymeren aus 1 und von Copolymeren aus 1 und 3 Segmente enthalten, die in Helixform mit vorherrschendem Drehsinn vorliegen. Kein Beweis für das Vorliegen dieses Typs wurde im Fall der Polymeren aus 2 erhalten. Die Konformationsanalyse von Molekülmodellen zeigt, daß Rechtshelices in den Polymeren aus 1 mit absoluter R-Konfiguration bevorzugt sind, wie beim Poly[(R)-4-methyl-1-hexen] gefunden wurde. Die Beziehungen zwischen der Konformation der Makromoleküle und den CD-Kurven im Bereich von 275-185 nm sind im Einklang mit frühern Ergebnissen, die im Fall von Copolymeren aus Styrol mit optisch aktiven α-Olefinen erhalten wurden.
    Notes: The chiroptical properties of stereoregular polymers of optically active 4-phenyl-1-hexene (1) and 5-phenyl-1-heptene (2) as well as of the copolymers of 1 with 4-methyl-1-pentene (3) were investigated. The comparison of the rotatory power and of the CD spectra in the spectral region of the π→π* electronic transitions of the aromatic chromophore of these polymers with the corresponding properties of optically active phenylalkanes allows the conclusion that the macromolecules of the homopolymer of 1 as well as of its copolymer with 3 contain chain blocks in helical conformation with a predominant direction of the screw. No evidence of this type was obtained for the polymers from 2. Conformational analysis based on molecular models shows that in the case of 1 having R absolute configuration, the favoured direction of the screw is the right handed one as found for poly[(R)-4-methyl-1-hexene]. The relationships between the conformation of the macromolecules and CD of the phenyl chromophore between 275 and 185 nm are consistent with previous results concerning copolymers of styrene with optically active α-olefins.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021740104
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  • 5
    Electronic Resource
    Electronic Resource
    Optically active hydrocarbon polymers with aromatic side chains, 10Part 9: cf.7.. Synthesis and properties of homopolymers and copolymers of 6-vinylchryseneDedicated to Prof. P. Pino on the occasion of the 60th anniversary of his birthday. (1982)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 183 (1982), S. 103-114 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis of 6-vinylchrysene (1) starting from chrysene is described. The study of the polymerizability of 1 by conventional radical, cationic, and Ziegler-Natta procedures indicates the tendency of 1 of give head-to-tail polymeric products with a similar degree of polymerization independent of the catalytic system. Copolymers of 1 with optically active (-)-menthyl acrylate (2), (-)-menthyl methacrylate (3), and (S)-4-methyl-1-hexene (4), were also prepared. No apparent copolymerization of 1 with optically active alkyl vinyl ethers occurred by cationic initiation. Spectroscopic and chiroptical properties are presented to support the formation of copolymer macromolecules. Finally, the differential dichroic absorption measurements allow one to stress that in optically active vinylaromatic copolymers the extent of preferential asymmetry, induced by the dissymmetric field of units derived from the optically active nonaromatic comonomer, increases with increasing bulkiness and polarizability of the vinylaromatic comonomer.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1982.021830109
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  • 6
    Electronic Resource
    Electronic Resource
    The role of hafnium in supported titanium/hafnium catalysts for olefin polymerization (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 15 (1989), S. 147-165 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several MgCl2-supported catalysts containing different amounts of titanium and hafnium were prepared. These systems are active for the polymerization of ethylene and α-olefins as well as for their copolymerization, giving much broader molecular weight distributions as compared with similar systems containing titanium only. Polymer properties, such as melt flow index and shear sensitivity can be varied by catalyst composition and addition of a Lewis base (ethyl benzoate). Gel permeation chromatography curves obtained in a single reactor (one-stage process) are comparable to those obtained in two reactors (two-stage process). An analysis of comparative kinetics for various conditions and the corresponding polymer properties suggests that Hf-containing sites produce much longer chains than do Ti-containing sites; at the same time Hf-containing sites display lower activity and higher tendency to interact with ethyl benzoate. Similar investigations with model catalysts are described to support these hypotheses.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.020151989115
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  • 7
    Electronic Resource
    Electronic Resource
    Stereoselective copolymerization of racemic α-olefins with ethylene by isospecific Ziegler-Natta catalyst (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 923-933 
    Details
    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: Copolymere aus Äthylen mit racemischem und optisch aktivem 3,7-Dimethyl-1-octen (3,7-DM-1-O) wurden durch isospezifische ZIEGLER-NATTA-Katalysatoren hergestellt. Die Copolymeren aus racemischem 3,7-DM-1-O wurden durch Chromatographie an kristallinem optisch aktivem Poly[(S)-3-methyl-1-penten] in Fraktionen verschiedenen optischen Drehsinnes getrennt. Die Wirksamkeit der Trennung ist sehr ähnlich der, die für isotaktische Homopolymere aus racemischem 3,7-DM-1-O erhalten wurde. Die fraktionierte Fällung von beiden Copolymeren wurde auch ausgeführt, um die Verteilung der Comonomeren zu untersuchen. Die Ergebnisse schließen eine völlige sterische Kontrolle durch das wachsende Kettenende aus. Die Stereoselektivität wird besser durch die Anwesenheit von asymmetrischen katalytischen Komplexen erklärt, die im isotaktischen Sinne stereospezifisch sind.
    Notes: Copolymers of ethylene with racemic and optically active 3,7-dimethyl-1-octene (3,7-DM-1-O) have been prepared in the presence of ZIEGLER-NATTA isospecific catalysts. The copolymers of racemic 3,7-DM-1-O have been separated in fractions having optical activity of opposite sign by chromatography on optically active poly[(S)-3-methyl-1-pentene]. The degree of separation obtained is very close to that found for the isotactic homopolymer of 3,7-DM-1-O. The fractional precipitation of both types of copolymers has been also carried out in order to obtain information on the distribution of the comonomers. The results exclude a mere steric control by the growing chain end. The stereoselectivity can be better explained on the basis of the presence of asymmetric catalytic complexes, which are stereospecific in the isotactic sense.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021750319
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  • 8
    Electronic Resource
    Electronic Resource
    Induced optical activity in copolymers of (-)-menthyl acrylate with styrene (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 3619-3623 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021771212
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  • 9
    Electronic Resource
    Electronic Resource
    Radical bulk functionalization of polyethylenes with ester groups (1992)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 179-186 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The radical functionalization of different types of polyethylene, such as high-density (HDPE) and linear low-density (LLDPE) polyethylene, with diethyl maleate (DEM) as a polar functional monomer and dicumyl peroxide (DCP) as radical initiator was investigated, and conditions for obtaining a controlled degree of functionalization and a low amount of degradation products without crosslinking were determined. Attention was paid to achieve a moderate functionalization of the polymer, in order to limit the modification of the mechanical and physical properties of the polyolefins. The molecular weight distribution of some of these polyethylenes was only moderately affected by the functionalization reaction. A critical discussion of the results outlines the fundamental role of process parameters such as stirring rate and heat exchange.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1992.021930117
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  • 10
    Electronic Resource
    Electronic Resource
    Optical acitivity and photochromism of the azo chromophore bound to poly(L-glutamic acid) (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 799-804 
    Details
    ISSN: 0006-3525
    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/bip.1978.360170319
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