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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] X-ray analysis, circular dichroism, receptor binding and biological potencies of chemically modified insulins suggest that the conformation of the insulin molecule is critical to the formation of both the zinc insulin hexamer and the insulin–receptor complex. Results are consistent with an ...
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 65 (1978), S. 115-116 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 62 (1975), S. 542-544 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 4
    Electronic Resource
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    Springer
    Colloid & polymer science 255 (1977), S. 819-819 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The thermal degradation of some acrylonitrile copolymers in air at temperatures up to 300 °C has been studied, and the following results obtained: For the polymers studied (polyacrylonitrile, poly-acrylonitrile contraining 2-vinyl-pyridine comonomer, and the commercial fibres Dralon, Orlon 42 and Orlon 74) a correlation was found between the temperatur of the exotherm determined by differential thermal analysis, and the temperature at which discoloration became appaten. Carboxylate groups introduced into polyacrylonitrile by alkaline hydrolysis shift this exotherm only slightly to lower temperatures. But the effect of incorporated pyridine moietics is more obvious. That means that the degree of nucleophility is important for the initiation of nitrile group oligomerisarion by comonomers. Agreement was found between the temperature of the exotherms and the temperatures at which maximum shrinkage at zero stress occurred, and it was concluded that shrinkage at this temperature was due to the formation of polymers with an angled ladder structure. Isothermal thermo-oxidation in the temperature range 180–220 °C resulted in a sharp decrease in the uptake of basic dyestuffs. Since dye uptake was increased by treatment with alkali, this different behaviour enabled damage resulting from thermal oxidation or alkaline hydrolysis to be distinguished. The reduced uptake of dye following thermal treatment cannot be explained by chemical reaction of the carbonyl groups but is due to alterations of the physical polymer-structure.
    Notes: Zusammenfassung Der temperatur-programmierte und isotherme Abbau einiger comonomerhaltiger Acrylnitrilfasern wurde bis maximal 300 °C unter Luft untersucht; dabei wurden die fogenden Ergebnisse erhalten: Bei der temperatur-programmierten Aufheizung korreliert für die untersuchten Polymeren (comonomer-freies und 2-vinylpyridinhaltiges Polyacrylnitril sowie Dralon, Orlon 42 und Orlon 74) der Beginn der thermischen Verfärbung und die Lage des exothermen Peaks im Differentialthermogramm. Durch alkalische Hydrolyse in Polyacrylnitril eingeführre Carboxylatgruppen verschieben den exothermen Peak im Differential-thermogramm nur geringfügig nach tieferen Temperaturen; der Einfluß von Pyridinresten ist dagegen deutlich ausgeprägter. Es wird gefolgett, daß der Grad der Nucleophilität der comonomeren Gruppen einen Einfluß auf die Initiietung der Cyclisierungs-reaktion der Nitrilgruppen hat. Die Übereinstimmung der maximalen, auf die Last 0 extrapolierten Schrumpfungstemperatur mit der Temperatur des exothermen Peaks im Differential-thermogramm wirdals Hinweis auf die Bildung einer gewinkelten leiterpolymer-Struktur gedeutet. Bei der isothermen Thermooxidation von Poly-acrylnitril wird im Bereich von 180–220 °C eine deutliche Abnahme des Farbstoffaufzichvermögens beobachtet, was auf physikalische Veränderungen der Faserstruktur zurückgeführt wird. Eine Verringerung des Anfärbevermögens durch chemische Reaktionen der Carboxylgruppen wird ausgeschlossen. Da im Gegensatz zur thermischen Behandlung bei einer Alkalibchandlung das Farbstoffaufnahmevermögen zunimmt, kann bei bekanntem Farbstoffsättigungswert der unbehandelten Faser auf die Art der Vorbehandlung (thermisch oder alkalisch) rückgeschlossen werden.
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  • 7
    Electronic Resource
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    Springer
    Colloid & polymer science 255 (1977), S. 444-451 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary The compounds Nα-acetyl-Nε-(γ-acetyl-glutamyl-a-[Ac-Glu-NHMe methylamide)lysine methylamide and Nθ-acetyl-alanyl-Nε-(γ-acetyl-glutamyl-(θ-leucine methylamide) lysine methylamide were synthesized as models for isopeptide crosslinks between peptide chain molecules. The acetylation with acetic anhydride in aqueous sodium bicarbonate yields racemization free N-acetyl aminoacyl derivatives. Through use of mixed anhydride coupling with methylamide the synthesis of aminoacyl methylamides was simplified in comparison with ester aminolysis. The isopeptide bond was synthesized by nucleophilic attack of the lysine e-amino group on the activated 2,4,5-trichlorophenyl-γ-glutamic acid ester or by mixed anhydride coupling. The isopeptides decomposed only above their melting points and were more hydrolytically stable than ε-(γ-glutamyl)lysine.
    Notes: Zusammenfassung Als Modellverbindungen für peptidgebundene Isopeptidquerbriicken wurden Naθ-Acetyl-Nε-(γ-acetyl-glutamyl-α-methylamid-)lysin-methylamid und Nα-Acetyk-alanyl-Nε-(γ-acetylglutamyl-α-leucin-methylamid-)lysinmethylamid synthetisiert. Die Acetylierung mit Acetanhydrid in wäßrigem Natriumhydrogenrcabonat ergab racemisierungsfreie N-Acetyl-aminoacylderivate. Durch gemischte Anhydridsynthese mit Methylamin vereinfachte sich die Synthese von Aminoacylmethylamiden im Vergleich zur Esteraminolyse. Die Isopeptidbindung wurde mittels Aminolyse des aktivierten 2,4,5-Trichlorphenyl-γ-glutaminsäureesters durch die ε-Aminogruppe des Lysins oder mit Hilfe der gemischten Anhydridsynthese geknüpft. Die Isopeptide zersetzten sich erst oberhalb ihrer Schmelzpunkte und waren hydrolysebeständiger als ε-(γ-Glutamyl-)lysin.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 257 (1979), S. 145-155 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary Wool and δ-Keratose were reacted at 20–60° for 4 hours with acylchlorides in dimethylsulfoxide with addition of pyridine or without a base. The ensuing crosslinking reaction. was due to formation of formaldehyde by reaction of the acid chlorides with the solvent dimethylsulfoxide. This explains the analytical data found: small weight changes participation of lysine, no participation of the carboxylic groups, disappearance of tyrosine during the acid hydrolysis. If the acyl chlorides are reacted with wool in the solvents dimethylformamide, dimethylacetamide, hexamethyl-phosphortriamide,γ-butyrolacton and methyl-pyrrolidone, normal acylation and corresponding weight increases were found.
    Notes: Zusammenfassung Wolle undδ-Keratose wurden mit Carbonsäure-chloriden in Dimethylsulfoxid mit Pyridinzusatz oder ohne Base bei 20–60 °C bis zu 4 Stunden umgesetzt. Die dabei eintretende Vernetzungsreaktion beruht auf der Bildung von Formaldehyd aus den Säurechloriden und Dimethylsulfoxid. Damit werden auch die Anafysendaten verständlich: geringe Gewichtsänderungen, Beteiligung des Lysins, keine Beteiligung der Carboxylgruppen, Verschwinden des Tyrosins erst nach saurer Totalhydrolyse. Läßt man Acylchloride in Dimethylformamid, Dimethylacetamid, Hexamethyl-phosphorsäuretriamid,γ-Butyrolacton und Methyl-pyrrolidon auf Wolle einwirken, so erfolgt N,O-Acylierung unter Gewichtszunahme.
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  • 9
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 5-Sulfoisophthalsäure läßt sich aus den Hydrolysaten von ε-Caprolactam-Copolyamiden mit Ionenaustauschchromatographie abtrennen und im Eluat mit Dünnschichtchromatographie, Papierhochspannungselektrophorese und Dünnschichtelektrophorese identifizieren. Nach Ermittlung des Comonomeren ist es möglich, den Gehalt an Isophthalsäure-5-natriumsulfonat direkt im Polymeren mit röntgenfluorometrischer Schwefelanalyse und flammenphotometrischer Natriumanalyse zu bestimmen.Eine Anwendung dieser Techniken auf zwei anionisch modifizierte Polyamid-6-Handelsfasern vom Differential-Dyeing-Typ (basic dyeable oder non dyeing Fasern) ergibt, daß sie Isophthalsäure-5-natriumsulfonat in einem Anteil von 2,5% enthalten.
    Notes: 5-Sulphoisophthalic acid can be separated from hydrolysates of ε-caprolactam copolyamides by ion-exchange chromatography and be identified in the eluate by thin-layer chromatography, high-voltage paper electrophoresis, and thin-layer electrophoresis. After the determination of the comonomers it is possible to determine the amount of the monosodium salt of 5-sulphoisophthalic acid (sodium 3,5-dicarboxybenzenesulphonate) directly in the polymer by X-ray fluorometric sulphur analysis and flame-photometric sodium analysis.The application of these techniques to two anionically-modified commercial polyamide-6 fibres of the differential dyeing type (basic dyeable or non-dyeing fibres) showed that they contain the monosodium salt of 5-sulphoisophthalic acid in an amount of 2.5%.
    Additional Material: 2 Tab.
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  • 10
    Publication Date: 1977-07-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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