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  • Chemistry  (36)
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  • 1
    Electronic Resource
    Electronic Resource
    Morphology of ultrahigh molecular weight polyethylene surface slid against steel (1987)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 189-192 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A morphological study was made to examine the friction and wear mechanisms of ultrahigh molecular weight polyethylene in air and water by means of transmission electron microscopy of a carbon replica film of a very thin layer of the polymer surface slid against a steel ball. Electron diffractions revealed that a molecular orientation with a typical fiber pattern was formed in the friction in air, while thin ribbon-like crystals with particular crystal orientations were formed in water in a way that the sliding took place on the crystallographic a - c plane, giving rise to a low friction coefficient of the polymer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1987.051500116
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallization of polypeptides in the course of polymerization, 5Part 4, cf.5.. Effect of the steric hindrance on the crystal growth by the side chainsDedicated to Professor Dr. ICHIRO SAKURADA on his 70th birthday (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 283-299 
    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: Es wurde der Einfluß der sterischen Hinderung durch Polypeptid-Seitenketten auf den Wachstumsmechanismus von Polypeptidkristallen während der Polymerisation untersucht. Dabei wurden von uns Untersuchungen der Kinetik der heterogenen Polymerisation von L-Valin-LEUCHS-Anhydrid (NCA), L-Isoleucin-NCA und L-Leucin-NCA mit Butylamin als Initiator in Acetonitril und der Strukturen sowie der Morphologie der gebildeten Polymere durchgeführt. In den Anfangsstadien der Polymerisation bildeten sich Oligomere, die in dünnen, bandförmigen Kristallen mit antiparalleler β-Konformation kristallisierten. Die molekularen Anordnungen in den Kristallen wurden mit Hilfe der Elektronenbeugung untersucht. In den späteren Stadien der Polymerisation setzten die gewachsenen Poly(L-valin)- und Poly-(L-iso1eucin)-Ketten die β-Struktur weiter fort, und ihre aktiven Enden wurden in den gebildeten Kristallen eingeschlossen, was ein-Einpendeln des Umsatzes bei einem niedrigen Wert zur Folge hatte. Poly(L-leucin) andererseits schien Kristalle mit gestreckten Ketten zu bilden, die zu einem sehr hohen Umsatz führten. Dies kann nicht ohne die Annahme erklärt werden, daß sich auf den in den Anfangsstadien der Polymerisation gebildeten β-Skelettkristallen α-Helix-Ketten bilden, wie dies im Falle des Poly(L-alanins) bereits früher berichtet wurde.
    Notes: In order to examine the effect of the steric hindrance by the polypeptide side chains on the growth mechanism of polypeptide crystals in the course of polymerization, we studied kinetics of the heterogeneous polymerization of L-valine N-carboxy anhydride (NCA), L-isoleucine NCA, and L-leucine NCA initiated by butylamine in acetonitrile and the structures and morphologies of the resultant polymers. In the early stages of polymerization, oligomers formed crystallized into thin ribbon-like crystals with the antiparallel β-conformation. The molecular arrangements in the crystals were studied by electron diffractions. In the later stages, the grown chains of poly(L-valine) and poly(L-isoleucine) continued to take the β-structure and their active ends were occluded in the crystals formed, which resulted in the levelling off of the conversion at a low value. On the other hand, poly(L-leucine) seemed to give the extended chain crystal, which made the conversion very high. This can not be accounted for without assuming the formation of β-helical chains onto the β-skeleton crystals formed in the early stages of polymerization as in the case of poly(L-alanine) reported previously.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021750129
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallization of polypeptides in the course of polymerization, 4. Studies on the molecular arrangement in oligo(L-alanine) crystals as polymerized (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 172 (1973), S. 221-226 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021720120
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallization of polypeptides in the course of polymerization, 6Part 5, cf.5.. Effect of the heteroatom attached to the β-carbon on the crystal growthDedicated to Professor Dr. ICHIRO SAKURADA on his 70th birthday (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 301-310 
    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: Der Wachstumsmechanismus von Polypeptiden, die das Heteroatom S am β- oder γ-Kohlenstoff enthalten und die in der beta;-Konformation bzw. der α-Helix-Konformation auftreten, wurde während des Verlaufs einer heterogenen Polymerisation untersucht. Dabei wurden von uns Untersuchungen der Kinetik der heterogenen Polymerisation von S-Methyl-L-cystein-LEUCHS-Anhydrid (NCA), S-Benzyloxycarbonyl-L-cystein-NCA und L-Methionin-NCA mit Butylamin als Initiator in Acetonitril und der Morphologie der gebildeten Polymere durchgeführt. Wie zu erwarten war, konnte bestätigt werden, daß polymere S-substituierte L-Cysteine, die nur die β-Struktur als Ordnungsform annehmen, Kristalle mit Kettenfaltung ergaben. In allen untersuchten Fällen bildeten sich in den Anfangsstadien der Polymerisation lange, bändchenförmige Kristalle, die mit fortschreitender Polymerisation sich zu runden, stäbchenförmigen Fasern verdickten. Für den Wachstumsmechanismus dieser Polymerkristalle wird ein mögliches Modell vorgeschlagen, wobei die unregelmäßige β-Struktur zugrunde gelegt wurde. Es konnte gezeigt werden, daß Poly(L-Methionin) mit α-Helixstruktur Kristalle mit gestreckten Ketten ergibt.
    Notes: In order to examine the growth mechanisms of polypeptides with a heteroatom, S, on the β- and γ-carbons which give the α-conformation and the α-helical conformation, resp., in the course of a heterogeneous polymerization, we have studied kinetics of the heterogeneous polymerization of S-methyl-L-cysteine N-carboxy anhydride (NCA), S-benzyloxycarbonyl-L-cysteine NCA and L-methionine NCA initiated by butylamine in acetonitrile and the morphologies of the resultant polymers. As was anticipated, it has been verified that poly-(S-substituted-L-cysteines), which take only the β-structure as the ordered form, gave the chain-folded crystals. In all the cases studied, long lath-like crystals formed in the early stages of polymerization thickened into round rod-like fibers as the polymerization proceeded. A possible model was proposed for the growth mechanism of these polymer crystals, taking into account the cross-β-structure. It has been revealed that poly(L-methionine) with the α-helical structure gave the extended chain crystals.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021750130
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  • 5
    Electronic Resource
    Electronic Resource
    Crystallization of poly(L-proline) in the course of polymerization (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 465-472 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The heterogeneous polymerization of L-proline N-carboxy anhydride was carried out in acetonitrile and benzene, using butylamine as the initiator. Polyproline I was formed in acetonitrile and polyproline II in benzene in the course of the polymerization. The conversion attained 99% and 66% after 1 week-polymerization in acetonitrile and benzene, resp. Extended chain crystals were obtained by the polymerization in acetonitrile. On the other hand, poly(L-proline) obtained by the polymerization in benzene gave aggregates into which many growing chain ends were occluded. The differences in the crystallization behaviour during the polymerization between the two different liquids may be due to the conformation of the resultant polymers. Polyproline I exhibits a cross-section per chain of 0.709 nm2, whereas polyproline II shows only one of 0,386 nm2. The wider the cross-section per chain the more the growing, active chain ends can react with the monomer, giving rise to a higher conversion. In contrast with the case of crystallization of such α-helical chains as poly(L-alanine) during polymerization, hexagonal lamellar crystals were formed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021800219
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  • 6
    Electronic Resource
    Electronic Resource
    Poly(L-lysine)/sulfated poly(vinyl alcohol)/acridine orange complex (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 193-199 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to clarify the arrangement of sulfated poly(vinyl alcohol) (PVS) chains about the α-helical poly(L-lysine) (PLL) chain in the previously reported complexes of PLL/46 mole-% sulfated poly(vinyl alcohol) (PVS-46) and PLL/PVS-95, induced circular dichroism was studied on PLL/PVS/acridine orange (AO) complexes in acidic aqueous solution. A positive ellipticity, [θ], of ca. 3 400 deg·cm2·dmol-1 at 465 am and small negative values of [θ] at 435 and 510 nm indicated a right-handed super helical arrangement of AO molecules about the right-handed α-helix of PLL, where PVS chains were intercalated. The amount of AO molecules responsible for the induced CD was estimated as low as a few mole-%. Taking into consideration the arrangement of ε-amino groups of the right-handed α-helical PLL and the distance among the neighboring ε-amino groups on the radial projection of the helix, the PVS chain segments could be arranged both in the right-handed and in the left-handed superhelices about the right-handed α-helix of PLL. In cases of the PLL/PVS-25/AO and PLL/PVS-30/AO complexes, no induced CD and a quite weak CD were obtained, resp., being consistent with random coil conformation of PLL in the PLL/PVS-25 and PLL/PVS-30 complexes mentioned previously.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1980.021810117
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational change of poly(L-lysine) by formation of complexes with poly(styrene sulfonate) (1980)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 497-506 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Circular dichroic studies were made on the conformational change of poly(L-lysine) (PLL) by complex formation with sulfonated polystyrenes (PSS) as functions of pH, temperature and polymer compositions in comparison with the complexes of PLL with sulfated poly(vinyl alcohol) (PVS). The coil-to-helix transition of PLL by complex formation at neutral and acidic pHs, which took place in the PLL/PVS (with high degrees of sulfation) complexes, was prevented in the PLL/PSS complexes due to the less chain flexibility of PSS than PVS. Above pH 11, the α-helix of PLL was partially broken into random coil by complex formation with PSS. The drastic decrease in the solution viscosity by the complex formation revealed a large contraction of PSS chain and subsequently a large strain of the α-helical PLL chain so as to give the breakdown of the α-helix. This is denoted a strain-induced conformational change of PLL. It was found that the α-helix of PLL was thermally stabilized by the complex formation with PSS as in the case of PLL/PVS complexes. A β-to-α transition of PLL by the complex formation with PSS was also found, while the β-form was maintained in the PLL/PVS (with high degrees of sulfation) complexes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1980.021810216
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  • 8
    Electronic Resource
    Electronic Resource
    Direct polymerization of N-carboxy anhydride of L-glutamic acid (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 2127-2137 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new method of polymerization of the N-carboxy anhydride (NCA) of glutamic acid is presented by which poly(glutamic acid) is obtained directly from the NCA without protecting its carboxyl group. The principle underlying is that by adjusting the mole ratio of the initiator butylamine, [I], to the monomer, [A], butylamine can be used as protecting agent for the carboxyl group of the NCA so that the rest of butylamine acts as initiator in the heterogeneous polymerization in acetonitrile. Quantitative conversion was obtained for an [A]/[I] ratio of 1. In analogy to other heterogeneous polymerizations of NCAs in acetonitrile, this is due to the formation of the helix during polymerization, which was confirmed by IR absorption and X-ray diffraction measurements. As the [A]/[I] ratio increases, the conversion, the helix content of the resultant polymer, and the amount of butylamine combined with it decrease drastically. It is suggested that “copolymerization” of the amine-protected and unprotected NCAs occurs, giving rise to a partially helical chain, whose contents of the amine-protected side chains and accordingly of the helix are the higher the smaller the [A]/[I] ratio.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820802
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  • 9
    Electronic Resource
    Electronic Resource
    Crystallization of polypeptides in the course of polymerization, IIIPart II: cf.1.. Further studies on the growth mechanisms of poly(L-alanine) crystals (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 169 (1973), S. 301-321 
    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: Zum Zweck der Prüfung eines früher vorgeschlagenen Mechanismus der Bildung von gestrecktkettigen Kristallen im Verlauf der heterogenen Polymerisation des LEUCHS schen Anhydrids von L-Alanin in Acetonitril wurden Oligo-L-Alanine hergestellt und deren Löslichkeit, Konformation und Kristallisationsverhalten in verschiedenen Lösungsmitteln untersucht.Es zeigte sich, daß die in Acetonitril wachsenden Ketten in Form der β-Modifikation auskristallisieren, sobald sie einen Polymerisationsgrad von 3 erreicht haben. Infolge der antiparallelen Anordnung der Ketten in der β-Modifikation scheint ein weiteres Wachstum der gebildeten Keime nicht möglich, so daß auf der „Hauptkette“ mit-Modifikation die Ketten zunächst im amorphen Zustand weiterwachsen. Sobald die wachsenden Ketten jedoch einen Polymerisationsgrad von 10-13 erreicht haben, beginnen sie in Form der α-Helix zu kristallisieren. Infolge des topochemischen Charakters der Reaktion ist diese kritische Kettenlänge, die zur Ausbildung der α-Helix nötig ist, geringer als für die entsprechenden bereits synthetisierten Oligomeren in Lösung.Die im Anfangsstadium der Polymerisation gebildeten Keime mit β-Modifikation bleiben im weiteren Verlauf der Polymerisation erhalten.Der Polymerisationsverlauf in den Lösungsmitteln Dioxan und Propionitril wurde ebenfalls untersucht. Ein Vergleich der Ergebnisse zeigt, daß der besonders günstige Verlauf der Reaktion in Acetonitril durch eine Dipol-Dipol-Wechselwirkung zwischen Lösungsmittel und Polypeptid bedingt sein könnte.
    Notes: In order to establish the mechanism proposed previously for the formation of the extended chain crystals during the heterogeneous polymerization of the LEUCHS anhydride 4-methyl-2,5-oxazolidinedione (L-alanine NCA) in acetonitrile, oligo-L-alanines were prepared by purely organic chemical methods. Their solubility, conformations in various solvents and those in the crystallized states were studied and compared with those in the crystals formed directly in the course of the heterogeneous polymerization. It was found that the growing chain molecules became insoluble in acetonitrile and crystallized into the β-conformation when they attained a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {\rm{DP}} $\end{document} of 3.As the growing chains in the course of the heterogeneous polymerization attained \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\rm{DP}}$\end{document} of 10-13 (i.e. 7-10 from the basal plane of the original skeleton crystals) by further polymerization, they crystallized into the α-helical conformation. Due to the topochemical nature of the chain growth, this critical length for the formation of the α-helix is shorter than that found in solution for the corresponding oligomers already synthesized (i.e., \documentclass{article}\pagestyle{empty}\begin{document}$\overline {\rm{DP}}$\end{document} 〉 10).It was also shown that the crystalline nuclei with the β-conformation, formed in the very early stages of the polymerization, remain throughout the polymerization.In order to examine the rôle of acetonitrile in this particular type of polymerization, the polymerization of L-alanine NCA was studied also in dioxane and propionitrile. The chains grown from the basal plane of the skeleton crystals with the β-conformation remain in some state like random coils until they attain the critical length for the formation of the α-helix. This critical length seems to depend on the solvation power (including the steric factor) of the solvent used. In the case of acetonitrile, the dipole-dipole interaction with polypeptides may play an important rǒle in this type of solvation.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021690128
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  • 10
    Electronic Resource
    Electronic Resource
    Formation of polyglycine crystals in the course of polymerization of glycine N-carboxy anhydride initiated by primary diamines (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 2481-2489 
    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 heterogene Polymerisation des Leuchs′schen Anhydrids von Glycin (2,5-Dioxo-1-oxa-3-azacyclopentane) wurde in Acetonitril unter Verwendung verschiedener primärer Diamine als Initiatoren wie Äthylendiamin (ED), Hexamethylendiamin (HM) und Bis(4-aminophenyl)äther (AP) durchgeführt und mit der bereits berichteten entsprechenden Polymerisation mit Butylamin verglichen. Elektronenmikroskopische Beobachtungen zeigten, daß die ausgefallenen Polymere meist aus Sphärolithen bestanden. Die Konformation des Polyglycins wie es mit allen Initiatoren erhalten wurde, war in der Form des Polyglycins I. Die scheinbare Kristallinität der erhaltenen Polymere war für den Fall der AP-initiierten Polymerisation niedrig, verglichen mit den durch ED oder HM initiierten Polymerisationen. Es wurde ein Mechanismus für das Wachstum der im Verlauf der Polymerisation entstandenen Polyglycin-Kristalle vorgeschlagen.
    Notes: The heterogeneous polymerization of glycine N-carboxy anhydride (2,5-dioxo-1-oxa-3-azacyclopentane) was carried out in acetonitrile using various kinds of primary diamines as initiators such as ethylene diamine (ED), hexamethylenediamine (HM) and bis(4-aminophenyl) ether (AP) comparing with butylamine previously reported. Electron microscopic observations revealed that most of the precipitates were spherulites. The conformation of polyglycine obtained from all the initiators used, was in the form of polyglycine I. The apparent crystallinity of the resultant polymer was low in the case of AP-as compared with ED-or HM-initiated polymerizations. A growth mechanism of polyglycine crystals formed in the course of polymerization has been proposed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770818
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