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  • 2000-2004
  • 1990-1994  (6)
  • 1970-1974  (2)
  • 1950-1954
  • 1940-1944
  • Chemistry  (6)
  • Hypericin  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A convenient semisynthetic route to hypericin (1993)
    Springer
    Monatshefte für Chemie 124 (1993), S. 339-341 
    Details
    ISSN: 1434-4475
    Keywords: Emodin ; Emodin anthrone ; Hypericin ; Cortex frangulae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Eine semisynthetische Route zur Darstellung von Hypericin unter Verwendung vonCortex frangulae als Ausgangsmaterial wurde erarbeitet. Das daraus einfach und in guten Ausbeuten isolierte Emodin wurde mit Hilfe von SnCl2 zu Emodinanthron reduziert. Letzteres wurde dann über eine bekannte oxidative Dimerisierung und Photocyclisierung zu Hypericin umgesetzt.
    Notes: Summary A semisynthetic route to produce hypericin was established usingCortex frangulae as the starting point. The emodin isolated from it easily and in good yield was reduced to emodin anthrone by means of SnCl2. The latter was reacted via a known oxidative dimerization and photocyclization reaction into hypericin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810594
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  • 2
    Electronic Resource
    Electronic Resource
    On the homo- and heteroassociation of hypericin (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 753-762 
    Details
    ISSN: 1434-4475
    Keywords: Hypericin ; Homoassociation ; Heteroassociation ; Human serum albumin complex ; Stacking ; Solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Hypericin zeigt ein kompliziertes Homo- und Heteroassoziationsverhalten. Während Hypericin in den üblichen polaren Lösungsmitteln bis zu einer Konzentration von 10−3 Mol/l monomolekular löslich ist, führt die Gegenwart von Wasser zur Ausbildung von Homoassoziaten. Wie aus spektroskopischen Messungen abgeleitet wurde, zeigen diese Homoassoziate ein Stapelungsmuster ähnlich jenem des kristallinen Materials. Tetrahydrofuran scheint eine Ausnahme zu sein, da in diesem Tautomerisierung zum 1,6-Dioxotautomer führt. Für die Heteroassoziation beobachtet man zwei Verhaltenstypen. In der Mehrzahl der Fälle bildet Hypericin Homoassoziate, welche dann durch Heteroassoziation mit dem Kosolvat zu stabilen Lösungen führen. Nur mit Humanserumalbumin wird ein spezifisches Heteroassoziat gebildet. Durch Konkurrenzreaktion konnte abgeleitet werden, daß Hypericin an die aktive Stelle der IIIA-Subdomäne des Proteins bindet.
    Notes: Summary Hypericin exhibits rather complicated homo- and heteroassociation behavior. Whereas in common polar solvents hypericin dissolves monomolecularly up to concentrations of 10−3 mol/l, the presence of water in these solvents leads to homoassociation. As derived by spectroscopic measurements, these homoassociates exhibit a stacking pattern similar to the one observed for the crystalline material. Tetrahydrofuran seems to be an exception, as it is the only solvent which results in 1,6-dioxo tautomer formation. Heteroassociation of hypericin involves two distinct types of behavior. In the majority of cases, hypericin forms homoassociates which then heteroassociate with the co-solvate to yield stabilized solutions of these homoassociates. Only with human serum albumin a specific heteroassociate is formed. By means of competition experiments it could be established that hypericin is binding to the active site of the IIIA subdomain of the protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01277637
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  • 3
    Electronic Resource
    Electronic Resource
    Structure elucidation of a Pyoverdin Produced by Pseudomonas aeruginosa ATCC 27 853 (1993)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 335 (1993), S. 83-87 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The primary structure of a pyoverdin (Pa TII) isolated from an iron deficient culture medium of Pseudomonas aeruginosa ATCC 27 853 has been elucidated by spectroscopic methods and degradation studies. Total assignment of 1H and 13C resonances as well as sequential information were achieved by two-dimensional NMR techniques: HOHAHA1, NOESY, HSQC and HMBC. The structure consists of the common pyoverdin chromophore 5-amino-2,3-dihydro-8,9-dihydroxy-1H-pyrimido [1,2-a]quinoline-1-carboxylic acid with succinic acid bound amidically to its amino group and the carboxyl group linked to the N-terminus of D-Ser-D(CHO) OHOrn-L-Orn-Gly-D-aThr-L-Ser-L-cOHOrn. According to the short-hand nomenclature suggested in [2, 3] the pyoverdin may be described as pyoverdin-Q-so′ OGtaSo′*-SUC.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19933350113
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  • 4
    Electronic Resource
    Electronic Resource
    Glass transition temperature as a guide to selection of polymers suitable for PTC materials (1973)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 13 (1973), S. 462-468 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: It has been shown that the only way to predict the size of the PTC effect displayed by a crystalline polymer when filled with conductive particles is through the knowledge of the glass transition point of the polymer. The size of the PTC anomaly is found to decrease sharply with rise in glass transition temperature and for a polymer to be a useful PTC material its glass transition must be below 0°C. It has not been possible to explain this relationship by any of the current theories of the PTC mechanism in filled polymers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760130611
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  • 5
    Electronic Resource
    Electronic Resource
    Stability of polymer composites as positive-temperature-coefficient resistors (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 706-716 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: This is a study of materials which are positive-temperature-coefficient resistors. Such materials, composed of conductive particles dispersed in a crystalline polymeric matrix, have been found to be of limited stability. An example is carbon black in high-density polyethylene. On repeated cycling through the anomaly temperature or on extensive heating at or above the anomaly temperature, the room temperature resistivity rises and the anomaly height falls to zero. This phenomenon has been shown to be caused by the absorption of oxygen by the polymer matrix which alters the structure, reduces the crystallinity, and induces an unusual form of crosslinking of a reversible nature.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760141009
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  • 6
    Electronic Resource
    Electronic Resource
    106. Flockung von Klärschlamm mit Sedipur im Zylinderrührer (1994)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 66 (1994), S. 1222-1223 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3306609107
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  • 7
    Electronic Resource
    Electronic Resource
    New Perspectives in Polyoxometalate Chemistry by isolation of compounds containing very large moieties as transferable building blocks: (NMe4)5[As2Mo8V4AsO40] · 3H2O, (NH4)21[H3Mo57V6(NO)6O183(H2O)18] · 65 H2O, (NH2Me2)18(NH4)6[Mo57V6(NO)6O183(H2O)18] · 14 H2O, and (NH4)12[Mo36(NO)4O108(H2O)16] · 33 H2O (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 599-619 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Neue Perspektiven in der Polyoxometallatchemie durch Isolierung von Verbindungen mit sehr großen übertragbaren Baueinheiten: (NMe4)5[As2Mo8V4AsO40] · 3H2O, (NH4)21[H3Mo57V6(NO)6O183(H2O)18] · 65 H2O, (NH2Me2)18(NH4)6[Mo57V6(NO)6O183(H2O)18] · 14 H2O und (NH4)12[Mo36(NO)4O108(H2O)16] · 33 H2ODie Verbindungen (NMe4)5[As2Mo8V4AsO40] · 3 H2O 2a, (NH4)21[H3Mo57V6(NO)6O183(H2O)18] · 65 H2O 3a, (NH2Me2)18(NH4)6[Mo57V6(NO)6O183(H2O)18] · 14 H2O 3b und (NH4)12[Mo36(NO)4O108(H2O)16] · 33 H2O 4a (3a und 4a sind in der Literatur bezüglich ihrer Zusammensetzung, Strukturen und der Oxidationszustände der Metallzentren nicht korrekt beschrieben worden), die zum Teil extrem große isolierte anionische Spezies enthalten, wurden dargestellt (darunter 3a, 3b und 4a in relativ hoher Ausbeute) und durch vollständige Kristallstrukturanalyse sowie durch IR-/Raman-, UV/VIS/NIR- und ESR-spektroskopische Methoden sowie mit Hilfe von vorläufigen magnetischen Suszeptibiltätsmessungen, Redoxtitrationen, Bindungsvalenzsummierungen, Elementaranalysen und thermogravimetrischen Studien charakterisiert. Perspektiven hinsichtlich der Synthese besonders großer nanodimensionierter Spezies werden im Zusammenhang mit den, in den Verbindungen 3a, 3b und 4a auftretenden, großen übertragbaren {Mo17} Baueinheiten diskutiert. Diese {Mo17} Baueinheit ist auch am Aufbau der Verbindung Na3(NH4)12[H15Mo57Fe6(NO)6O183(H2O)18] · 76 H2O 7a beteiligt.
    Notes: The compounds (NMe4)5[As2Mo8V4AsO40] · 3 H2O 2a, (NH4)21[H3Mo57V6(NO)6O183(H2O)18] · 65 H2O 3a, (NH2Me2)18(NH4)6[Mo57V6(NO)6O183(H2O)18] · 14 H2O 3b and (NH4)12[Mo36(NO)4O108(H2O)16] · 33 H2O 4a (3a and 4a were not correctly reported in the literature regarding to their composition, structures and the oxidation states of the metal centres) which contain large isolated anionic species, have been prepared (among them 3a, 3b, and 4a in rather high yield) and characterized by complete crystal structure analysis as well as IR/Raman, UV/VIS/NIR, ESR spectroscopy and magnetic susceptibility measurements, redox titrations, bond valence sum calculations, elemental analyses and thermogravimetric studies. Perspectives for polyoxometalate chemistry referring to the synthesis of “extremely” large nanoscaled species are discussed, together with the occurrence of a large transferable {Mo17} building block in the compounds 3a, 3b and 4a which also exists in the corresponding iron compound Na3(NH4)12[H15Mo57Fe6(NO)6O183(H2O)18] · 76 H2O 7a.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200405
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and examination of chiral liquid crystalline side chain polymers (1994)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 45 (1994), S. 21-25 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Substituted poly(methylsiloxane)s connected by a spacer with a biphenyl system that is esterificated with a chiral α-chlorocarboxylic acid have been synthesized and characterized. Their liquid crystalline properties have been studied by differential scanning calorimetry (DSC), polarization microscopy, electro-optical methods and X-ray diffraction. Most of the synthesized compounds and polymers have liquid crystalline phases, mainly smectic phases.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1994.010450105
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