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  • 1
    Electronic Resource
    Electronic Resource
    The use of a new bioresorbable barrier for guided bone regeneration in connection with implant installation. Case reports. (1994)
    Copenhagen : Munksgaard International Publishers
    Clinical oral implants research 5 (1994), S. 0 
    Details
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This report presents 4 cases with 6 implant exposures after the installation of Bråemark System® implants which called for treatment applying the guided bone regeneration technique. A bioresorbable barrier (GUIDOR® Matrix Barrier) was used to cover the defects, 4 defects with and 2 without the support of autologous bone chips. Complete bone filling was found in 4 (2 without and 2 with bone chips) and partial filling in 2 (with bone chips) of the treated defects, as registered at the abutment connection 6–7 months after surgery. Besides its ability to serve as a barrier for guided bone regeneration, it was found that the matrix barrier had the following properties; biocompatibility observed as uneventful tissue healing, malleability facilitating the clinical handling and ability to be resorbed within 6 to 7 months, as evaluated by clinical inspection. The observations of the present case reports indicate that the tested barrier may be used for guided bone regeneration in connection with implant installation. It is advisable, however, to use a supporting material to prevent barrier collapse, although bone regeneration can be achieved in certain situations without such material if the defect morphology is favourable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0501.1994.050309.x
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  • 2
    Electronic Resource
    Electronic Resource
    Concerning the question of covalent bonding in hypericin-chromoproteins: Schiff base formation? (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 313-323 
    Details
    ISSN: 1434-4475
    Keywords: Hypericin ; Stentor ; Schiff base ; Anthraquinone imines ; Aminoanthraquinones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Abhängig von den Reaktionsbedingungen gabenperi-hydroxylsubstituierte Anthrachinone, wie 1,8-Dihydroxyanthrachinon oder 1,4-Dihydroxyanthrachinon, mit Propylamin, Isopropylamin und einem Lysinderivat eine Reihe von Imino- und Amino-Substitutionsprodukten oder Addukten. Allerdings widerstand Hypericin unter Variation der Reaktionsbedingungen einer solchen Derivatisierung. Deshalb ist die Hypothese, daß Hypericin in seinen Photopigmenten über eine Schiffsche Base mit der ε-Aminogruppe eines Lysinrestes oder mit einer terminalen Aminogruppe verknüpft ist, eher unwahrscheinlich.
    Notes: Summary Depending on the reaction conditions,peri-hydroxy substituted anthraquinones like 1,8-dihydroxyanthraquinone and 1,4-dihydroxyanthraquinone could be derivatized with ammonia, propylamine, isopropylamine, and a lysine derivative to yield a variety of imino and amino substitution and addition products. However, hypericin resisted such derivatization under a variety of reaction conditions. Therefore, the hypothesis that hypericin is bound to its apoprotein in photopigmentsvia a Schiff base to the ε-amino group of a lysine residue or a terminal amino group seems to be rather unlikely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811317
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D: Force field investigations (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 955-961 
    Details
    ISSN: 1434-4475
    Keywords: Fringelit D ; Stentorin ; Isostentorin ; Force Field Calculations ; Tautomerism ; Interconversion Barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Stereochemie und Tautomerie von Stentorin, Isostentorin und Fringelit D wurden mit Hilfe einer von MM2 abgeleiteten Kraftfeldmethodik untersucht. Für diese Pigmente wurde abgeleitet, daß die 7,14-Dioxotautomeren am stabilsten sind und daß sie durch eine Energielücke von etwa 50 kJ/Mol von den weniger stabilen Tautomeren getrennt sind. Diese drei Chinone liegen jeweils als Propeller- und Doppelschmetterlings-Konfomere vor, wobei letztere geringfügig stabiler als erstere sind. Verglichen mit Hypericin sind die Interkonversionsbarrieren zwischen diesen Konformeren, wie auch zwischen enantiomeren Konformeren desselben Typs, niederer. Sie wurden zu etwa 40 kJ/Mol abgeschätzt und lassen damit eine Isolierung von Enantiomeren unwahrscheinlich werden.
    Notes: Summary Stereochemistry and tautomerism of stentorin, isostentorin, and fringelit D were investigated using an MM2 derived force field method. For these pigments, the 7,14-dioxo tautomers were derived to be the most stable ones, with a gap of about 50 kJ/mol separating them from the less stable species. The three quinones display propeller and double butterfly conformers. The double butterfly conformers were found to be slightly more stable than the propeller conformers. Compared to hypericin the interconversion barriers between these conformers and between enantiomeric conformers of the same type are lower. They were estimated to be in the order of 40 kJ/mol; thus an isolation of enantiomers is improbable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00812710
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  • 5
    Electronic Resource
    Electronic Resource
    On the chemical nature of 10-dicyanomethylene-anthrone hydrazone (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 1121-1127 
    Details
    ISSN: 1434-4475
    Keywords: 10-Dicyanomethylene-9-anthrone hydrazone ; 10-Dicyanomethylene-9-anthrone ; N-Acetyl-10-dicyanomethylene-9-anthrone hydrazone ; (10-dicyanomethylene-9,10-dihydroanthracene-9-ylidene)-isopropylidene-hydrazine ; 9-Diazo-10-(dicyanomethylene)-9,10-dihydro anthracene ; Acetylation ; Oxidation ; Hydrolysis ; Semiemprical calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die chemische Natur von 10-Dicyanomethylen-9-anthronhydrazon wurde untersucht. Es wurde gezeigt, daß diese Verbindung, welche konjugierte Ylidenmalononitril- und Hydrazonfragmente enthält, keine für Ylidenmalononitrile charakteristischen Reaktionen, wie Reduktion und Michaeladdition eingeht, dafür aber typische Hydrazoneigenschaften zeigte. Es konnte hydrolysiert, acetyliert, mit Aceton zum entsprechenden Azin umgesetzt und zur Diazoverbindung oxidiert werden. Diese Eigenschaften wurden mit Hilfe von semiempirischen (AM1) und Kraftfeld-Rechnungen interpretiert.
    Notes: Summary The chemical nature of 10-dicyanomethylene-9-anthrone hydrazone was examined. It was shown that this compound bearing the conjugated ylidenemalononitrile fragment and hydrazonic moiety did not undergo transformations characteristic of ylidenemalononitriles,e.g., reduction andMichael addition, but possesses properties typical for hydrazones. Thus it could be hydrolyzed, acetylated, oxidized to yield the diazo compound, and reacted with acetone to form the corresponding azine. These properties were interpreted using semiempirical (AM1) and force field calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811520
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  • 6
    Electronic Resource
    Electronic Resource
    On the chemistry of pyrrole pigments, XCI: Copper complexes of pyridinologous linear tri- and tetra-pyrroles as cyclopropanation catalysts (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 325-333 
    Details
    ISSN: 1434-4475
    Keywords: Pyridinologous linear tri- and tetrapyrroles ; Copper chelates ; 1H-NMR spectra ; Configuration ; Conformation ; Cyclopropanation catalyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Zusätzlich zu zwei jüngst beschriebenen linearen pyridinologen Tri- und Tetrapyrrolen wurde ein biisochinolylanaloges System dargestellt und seine Geometrie aus Kernresonanzmessungen und Kraftfeldrechnungen abgeleitet. Die Kupferkomplexe dieser drei Liganden wurden isoliert und charakterisiert und als Katalysatoren für die Cyclopropanierung von Styrol eingesetzt. Die Ergebnisse waren mit jenen aus der Literatur zahlreicher Komplexe vergleichbar. Damit konnte gezeigt werden, daß solche Systeme prinzipiell als Katalysatoren Verwendung finden können.
    Notes: Summary In addition to two recently described pyridinologous linear tri- and tetrapyrroles a biisoquinologous system was prepared and its geometrical features derived by means of NMR measurements and force field calculations. The copper complexes of these three ligands were isolated and characterized, and then used as catalysts in the cyclopropanation of styrene. The results were found to be similar to those reported for a variety of catalysts in literature. Thus, it was demonstrated that these systems can be used in principle as catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811318
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  • 7
    Electronic Resource
    Electronic Resource
    A novel reaction of 11,11,12,12-tetracyanoanthraquinodimethane: The formation of 10-dicyanomethylene-anthrone hydrazone (1994)
    Springer
    Monatshefte für Chemie 125 (1994), S. 549-551 
    Details
    ISSN: 1434-4475
    Keywords: 11,11,12,12-Tetracyanoanthraquinodimethane ; 10-Dicyanomethylene-anthrone hydrazone ; Solvatochromic shift ; Non-linear optical properties ; Donor-acceptor system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Eine neue Reaktion von 11,11,12,12-Tetracyanoanthrachinodimethan — seine Umsetzung zum 10-Dicyanomethylen-anthronhydrazon durch Reaktion mit Hydrazin — wird beschrieben. Dieses Hydrazon könnte als Ausgangsmaterial für die Synthese von Anthracenderivaten dienen, zeigt aber auch selbst als konjugiertes Donor-Akzeptorsystem interessante physikalische Eigenschaften.
    Notes: Summary A novel reaction of 11,11,12,12-tetracyanoanthraquinodimethane — its transformation into 10-dicyanomethylene-anthrone hydrazone by reaction with hydrazine — is reported. This hydrazone seems to be a convenient starting material in the synthesis of anthracene derivatives and compounds incorporating anthracenic fragments, but is itself as a conjugated donor acceptor system a material with interesting physical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811847
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