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  • 1
    Electronic Resource
    Electronic Resource
    Rapid calcium release and proton uptake at the disk membrane of isolated cattle rod outer segments. 1. Stoichiometry of light-stimulated calcium release and proton uptake (1981)
    s.l. : American Chemical Society
    Biochemistry 20 (1981), S. 5500-5510 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00522a024
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  • 2
    Electronic Resource
    Electronic Resource
    Rapid calcium release and proton uptake at the disk membrane of isolated cattle rod outer segments. 2. Kinetics of light-stimulated calcium release and proton uptake (1981)
    s.l. : American Chemical Society
    Biochemistry 20 (1981), S. 5511-5516 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00522a025
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  • 3
    Electronic Resource
    Electronic Resource
    Metarhodopsin I/metarhodopsin II transition triggers light-induced change in calcium binding at rod disk membranes (1980)
    [s.l.] : Nature Publishing Group
    Nature 286 (1980), S. 638-640 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Intact cattle rod outer segments have been isolated according to Schnetkamp etal.9. Disk vesicles were obtained by sonication of intact rod outer segments in a medium containing sucrose, 600 mM; Ficoll 400, 5% v/v; HEPES, pH 7.0 2 mM, for 30 s at 40 W. The suspension also contained about 3-4 ,? of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/286638a0
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  • 4
    Electronic Resource
    Electronic Resource
    Optical probes for electrochemical events and for conformational changes in biological membranes (1980)
    Springer
    European biophysics journal 6 (1980), S. 18-19 
    Details
    ISSN: 1432-1017
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647496
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  • 5
    Electronic Resource
    Electronic Resource
    On the relation between rapid light-induced Ca2+ release and proton uptake in rod outer segment disk membranes (1983)
    Springer
    Molecular and cellular biochemistry 52 (1983), S. 37-48 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary In this paper we review our experiments on the light-induced Ca2+ release and proton uptake at the rod outer segment (ROS) disk membrane using flash-spectrophotometry and the indicating dyes arsenazo III and bromcresol purple. We used three different ROS preparations in order to locate the intracellular site of Ca2+ release. The ionophore A23187 was required to communicate the Ca2+ release to the indicator located in the external medium in both ROS with an intact and with a leaky plasma membrane. A23187 was also required to observe the Ca2+ released in the interior of vesicles prepared by sonication of ROS. From this we conclude that the site of Ca2+ release is located at the luminal side of the disk membrane, whereas this Ca2+ was not transported across the disk membrane under our experimental conditions and on the time scale of our experiments (20 s). Light-induced Ca2+ release was inhibited by electrolytes in the suspension medium provided that the electrolytes gained access to the compartment where Ca2+ was released. The effectivity to inhibit Ca2+ release markedly increased from monovalent to divalent to trivalent cations. The results strongly suggest that electrolytes (cations) act by screening the electrostatic potential at the disk membrane surface due to the presence of a net fixed negative surface charge. The surface potential controls the free Ca2+ concentration at the membrane surface and, therefore, controls the amount of Ca2+ bound to the disk membrane. The kinetics of light-induced Ca2+ release and proton uptake showed a similar dependence on the structural status of the ROS. In sonicated ROS almost linear Arrhenius plots were observed for metarhodopsin II formation, Ca2+ release and proton uptake (energy of activation 150 kJ/ mol). In intact ROS both Ca2+ release and proton uptake showed a nonlinear Arrhenius plot with rate constants up to 30-fold slower than metarhodopsin II formation. At temperatures above 10 °C a process other than metarhodopsin II formation rate limited both light-induced proton uptake and Ca2+ release (energy of activation 42 kJ/ mol). A model is discussed in which metarhodopsin II formation triggers the uptake of proton(s) into the disk membrane lowering the surface potential. A reduction potential of the surface in turn decreases the free Ca2+ concentration at the surface thereby causing the release of part of the bound Ca2+.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230587
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  • 6
    Electronic Resource
    Electronic Resource
    Fragmentierende Ringverengungen des 1:2-Addukts aus Pyridin und Acetylendicarbonsäure-dimethylester (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2467-2477 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fragmentative Ring Contractions of the 1:2-Adduct of Pyridine and Dimethyl Acetylene-dicarboxylateThe structure 1a is secured for the 1:2-adduct of pyridine and dimethyl acetylenedicarboxylate. Its UV/VIS and 1H NMR spectra are temperature-dependent. Dichromate oxidation of 1a produces not only the indolizine 3, but also the quinolizinone 4. The indolizines 8, 3, 9, and 10 are formed in the ratio 10:5:5:1 upon thermolysis of 1a at 220°C, whereas 4 is stable under these conditions. The complex ring contractions with fragmentations and in part rearrangements are classified and interpreted mechanistically (high energy valence tautomers; cyclopropane-, ylide-, zwitterion/diradical-intermediates). The gaseous and liquid further products of the thermolysis are compatible with the intermediacy of carbene and radical fragments. Analytical and spectroscopic data (UV, fluorescence, IR, 1H, 13C NMR, MS) as well as independent syntheses (3, 10) and the synthesis of the reference compound 12 secure the constitutions of the compounds.
    Notes: Für das 1:2-Addukt aus Pyridin und Acetylendicarbonsäure-dimethylester wird die Konstitution 1a gesichert. Die UV/VIS- und 1H-NMR-Spektren sind temperaturabhängig. Die Dichromat-Oxidation von 1a liefert nicht nur das Indolizin 3, sondern auch das Chinolizinon 4. Die Thermolyse von 1a bei 220°C ergibt die Indolizine 8, 3, 9 und 10 im Verhältnis 10:5:5:1, während 4 unter diesen Bedingungen stabil ist. Die komplizierten Ringverengungen mit Fragmentierungen und teilweise Umlagerungen werden klassifiziert und mechanistisch gedeutet (energiereiche Valenztautomere; Dreiring-, Ylid-, Zwitterion/Diradikal-Intermediate). Die gasförmigen und flüssigen weiteren Produkte der Thermolyse stehen im Einklang mit dem Auftreten von Carben- und Radikal-Fragmenten, die aus den formulierten Intermediaten entstehen sollten. Zur Konstitutionssicherung dienen analytische und spektroskopische (UV, Fluoreszenz, IR, 1H-, 13C-NMR, MS) Daten sowie unabhängige Synthesen (3, 10) und die Synthese der Referenzverbindung 12.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150709
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  • 7
    Electronic Resource
    Electronic Resource
    Cyclovinyloge Additionen von 1,3-Diphenylbenzo[c]furan an 1,3,5-Cycloheptatrien (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 618-629 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclovinylogous Additions of 1,3-Diphenylbenzo[c]furan to 1,3,5-Cycloheptatriene1,3-Diphenylbenzo[c]furan (1) reacts thermally with 3,4-dimethylenecyclobutene (2) and 1,3,5-cycloheptatriene (5) to give exo- and endo-Diels-Alder adducts. The reaction of 1 with potassium cycloheptatrienide leads to substitutive adducts (13, 14) at low temperature, but to [4 + 2]-ring closure (15) at higher temperatures, via the anionic intermediate 12. The photoaddition of 1 to 5 gives the exo- and endo-[4 + 2]-, endo-[4 + 6]-, exo-[4 + 4]- und cis-1,4(1,3)-substitutive adducts 7, 6, 16, 17 und 14, in divergence to recent literature data. The structures of the products are elucidated by 1H NMR spectra and in part by chemical transformations, their formation can be interpreted in terms of the approved diradical mechanism. The endo-/exo-isomerization of 16 into 19 proceeds solvolytically. The products 7 and 16 are formed out of 17 by suprafacial thermal 1,3-alkyl shifts. Further exo- und endo-[4 + 2]- as well as [4 + 4]-additions of 1 are achieved with dimethyl maleate (23, 24) and anthracene (26), resp.
    Notes: 1,3-Diphenylbenzo[c]furan (1) reagiert thermisch mit 3,4-Dimethylencyclobuten (2) und 1,3,5-Cycloheptatrien (5) zu exo- und endo-Diels-Alder-Addukten. Die Reaktion von 1 mit Kaliumcycloheptatrienid führt über das Anionzwischenprodukt 12 bei tiefer Temperatur zu Substitutionsaddukten (13, 14), bei höherer Temperatur dagegen zum [4 + 2]-Ringschluß (15). Die Photoaddition von 1 an 5 führt abweichend von Literaturangaben zu den exo- und endo-[4 + 2]-, endo-[4 + 6]-, exo-[4 + 4]- und cis-1,4(1,3)-Substitutions-Addukten 7, 6, 16, 17 und 14, deren Konstitution 1H-NMR-spektroskopisch sowie z. T. durch chemische Umwandlungen belegt wird und deren Bildung auf der Grundlage des bewährten Diradikalmechanismus gedeutet werden kann. Die endo-/exo-Isomerisierung von 16 zu 19 gelingt solvolytisch. Durch suprafaciale thermische 1,3-Alkylverschiebungen entstehen aus 17 die Produkte 7 und 16. Weitere exo- und endo-[4 + 2]- sowie [4 + 4]-Additionen von 1 werden mit Maleinsäure-dimethylester (23, 24) und Anthracen (26) erreicht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160221
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  • 8
    Electronic Resource
    Electronic Resource
    Thermische [2, 1, 3]-Eliminierung von Methanthiol aus einem 1,5-Benzothiazepin-Derivat (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1643-1646 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal [2,1,3]-Elimination on Methanethiol from a 1,5-Benzothiazepine DerivativeUpon heating to 200°C, the 1,5-benzothiazepine derivative 1 eliminates methanethiol to form the benzothiazole derivative 2, but not the 1,5-benzothiazepine 5. The structure of 2, is established by independent synthesis from 3, photolysis to give 4, spectroscopic data. The reaction of 1, to give 2 and methanethiol is termed a [2,1,3]-elimination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170433
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  • 9
    Electronic Resource
    Electronic Resource
    1,4-Addition von Kalium-cycloheptatrienid an (9-Phenyl-)Anthracen (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 3208-3211 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,4-Addition of Potassium Cycloheptatrienide to (9-Phenyl-)AnthraceneIn liquid ammonia the cycloheptatriene anion adds to anthracene (3) and 9-phenylanthracene (9) to give the anions 4 and 10, resp., which are quenched at -35°C to give the substitutive 1,4-adducts 5 and 11 + 12, resp. Upon heating up to 20°C the intermediate anion 4 cyclizes to the Diels-Alder product 6, which is quenched to give the asymmetric and symmetric [4 + 2]-adducts 7 and 8. The structures of the products have been established primarily by high-field 1H-NMR spectroscopy.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150924
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  • 10
    Electronic Resource
    Electronic Resource
    Photoadditionen von Anthracenen an 2,4-Hexadien und 1,3,5-Cycloheptatrien (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 630-644 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photoadditions of Anthracenes to 2,4-Hexadiene and 1,3,5-CycloheptatrieneElectronically excited 9-anthracenecarbonitrile (1*), in contrast to theoretical predictions, is trapped by 2,4-hexadiene to give the [4 + 4]-adduct 3 with a trans-double bond, which forms the [4 + 2]-adduct 4 above 0°C via suprafacial 1,3-shift. Also 1,3,5-cycloheptatriene (6) quenches 1* with the result of a thermolabile [4 + 4]-addukt 7 (→ 8). In addition to 8, further adducts (9, 10, 11, 12) are formed via isomeric diradicals. Anthracene (19*) and 6 generate the [4 + 6]-, [4 + 4]-, [4 + 2]-, substitutive, and peripheral adducts 20, 21, 22, 23, 24, and 24. 9-Phenylanthracene (25*) and 6 form the corresponding, partly isomeric, adducts (26; 29; 27, 28; 30, 31; 32). The reactions are interpreted in terms of diradical mechanisms. Numerous literature reports, which havealready been classified theoretically, are amended or corrected, the reasons for erroneous theoretical predictions are discussed. The diversity of products can be understood in detail by empirical extrapolations on the basis of the experimentally secured cyclovinylogy principle.
    Notes: Elektronisch angeregtes 9-Anthracencarbonitril (1*) wird von 2,4-Hexadien (2) entgegen theoretischen Erwartungen zum [4 + 4]-Addukt 3 mit trans-Doppelbindung abgefangen, aus dem oberhalb 0°C durch suprafaciale 1,3-Verschiebung das [4 + 2]-Addukt 4 entsteht. Auch 1,3,5-Cycloheptatrien (6) reagiert mit 1* zu einem thermolabilen [4 + 4]-Addukt 7 (→ 8). Daneben entstehen weitere Addukte (9, 10, 11, 12) über isomere Diradikale. Anthracen (19*) bildet mit 6 die [4 + 6]-, [4 + 4]-, [4 + 2]-, Substitutions- und Peripher-Addukte 20, 21, 22, 23, 24. Mit 9-Phenylanthracen (25*) und 6 gibt es die entsprechenden, z. T. stellungsisomeren, Addukte (26; 29; 27, 28; 30, 31; 32). Die Reaktionen werden an Hand von Diradikalmechanismen gedeutet. Zahlreiche bereits theoretisch klassifizierte Literaturangaben werden ergänzt oder berichtigt, die Gründe für die fehlerhaften theoretischen Vorhersagen diskutiert. Die Produktevielfalt kann durch empirische Extrapolation im Rahmen des experimentell gesicherten Cyclovinylogieprinzips detailliert verstanden werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160222
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