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  • 1
    Electronic Resource
    Electronic Resource
    A comparison of sequence complexity of nuclear and polysomal poly(A)+ RNA from different developmental stages ofXenopus laevis (1980)
    Springer
    Development genes and evolution 188 (1980), S. 187-193 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus ; Gastrula ; Early tadpole ; Poly(A)+ RNA ; cDNA hybridization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nuclear poly(A)+ and polysomal poly(A)+ RNA were isolated from gastrula and early tadpole stages of the amphibianXenopus laevis. Complementary DNA was synthesized from all RNA preparations. Hybridization reactions revealed that at least all abundant and probably most of the less frequent nuclear and polysomal poly(A)+ RNA species present at the gastrula stage are also present at the early tadpole stage. On the other hand, there are nuclear RNA sequences at the latter stage which appear, if at all, only at lower concentrations at the gastrula stage. The polysomal poly(A)+ RNA hybridization reactions suggest the existence of polysomal poly(A)+ RNA sequences at early tadpole stages which are not present in the corresponding gastrula stage RNA. By cDNA hybridization with poly(A)− RNA it could be shown that most of the poly(A)+ containing RNA sequences transcribed into cDNA were also present within the poly(A)− RNA. It was estimated, that these sequences are 10 fold more abundant within the poly(A)− polysomal RNA and 3–6 more abundant within the poly(A)− nuclear RNA as compared to the poly(A)+ RNAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00849047
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  • 2
    Electronic Resource
    Electronic Resource
    Cloning of cDNA sequences derived from poly(A)+ nuclear RNA ofXenopus laevis at different developmental stages: Evidence for stage specific regulation (1981)
    Springer
    Development genes and evolution 190 (1981), S. 97-102 
    Details
    ISSN: 1432-041X
    Keywords: Xenopus laevis ; Poly(A)+ nuclear RNA ; cDNA cloning ; Stage specificity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nuclear poly(A)+ RNA was isolated from gastrula and early tadpole stages ofXenopus laevis, transcribed into cDNA and integrated as double stranded cDNA by the G-C joining method into the Pst cleavage site of plasmid pBR 322. After cloning inE. coli strain HB 101 the clone libraries were hybridized to32P labelled cDNA derived from nuclear poly(A)+ RNA of the two different developmental stages. About 20% of the clones gave a positive hybridization signal thus representing RNA molecules of high and medium abundance. From these clones, some individual clones were identified containing sequences which are not present at the oocyte and gastrula stages but which are transcribed at the early tadpole stage of embryonic development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848402
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  • 3
    Electronic Resource
    Electronic Resource
    Über gespannte alkyl-aromatische Systeme, 5. Lithium-7bH-indeno[1,2,3-jk]fluorenid (1979)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 1380-1391 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Strained Alkyl-Aromatic Systems, 5. Lithium 7bH-Indeno[1,2,3-jk]fluorenideThe molecular structure of the title compound C19H11Li · 1/2 C6H6 (2) has been determined by X-ray structure analysis at -160°C: space group monoclin P21/a; a = 1114.2, b = 1482.9, c = 1008.1 pm, β = 117.99°; Z = 4. 2 is the first organolithium compound having a lithium ion in linear coordination with two hexahapto-bonded six-membered ring ligands in a sandwich fashion (fig. 3). An increase in strain energy for the ionisation of the hydrocarbon 1 to the carbanion 2 was calculated by empirical force field methods. The molecular geometry of 2 is consistent with both a simple electrostatic model and a MO-model (CNDO/2), the calculated Li⊕-positions deviate only 0.18 and 0.13 Å from experimental values.
    Notes: Die Molekülstruktur der Titelverbindung C19H11Li · 1/2 C6H6 (2) wurde durch Röntgenstrukturanalyse bei -160°C bestimmt: monoklin, Raumgruppe P21/a; a = 1114.2, b = 1482.9, c = 1008.1 pm, β = 117.99° Z = 4. 2 ist die erste Organolithium-Verbindung, in welcher Lithium-Ionen linear mit je zwei hexahapto-gebundenen Sechsring-Liganden „sandwich“-artig koordiniert sind (Abb. 3). Ein Anstieg der Spannungsenergie wurde für den Übergang des Kohlenwasserstoffs 1 in das Carbanion 2 nach empirischen Kraftfeld-Methoden berechnet. Die Molekülgeometrie von 2 steht in guter Übereinstimmung sowohl mit einem einfachen elektrostatischen Modell als auch mit einem MO-Modell (CNDO/2), nach denen sich die Li⊕-Positionen nur 0.18 bzw. 0.13 Å abweichend von den experimentellen Werten ergeben.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19791120432
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  • 4
    Electronic Resource
    Electronic Resource
    Gespannte alkyl-aromatische Systeme, 2. Kristallstruktur und Reaktionen des 7bH-Indeno[1,2,3-jk]fluorens (1975)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 108 (1975), S. 1807-1822 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Strained Alkyl-aromatic Systems, 2. Crystal Structure and Reactions of 7bH Indeno[1,2,3-jk]floureneAn X-ray structure analysis of 7bH-indeno[1,2,3-jk]fluorene (1) (space group rhombic Pnma; a = 8.298, b = 19.974, c = 7.367 Å;; z = 8/2) shows that the strain of the molecule causes a deformation of the aromatic ring C into a flat asymmetric boat form: The plane through C(12), C(12′), C(13), and C(13′) is inclined by 16.3 and 5.6° to the planes defined by the atoms C(12)-C(11)-C(12′) and C(13)-C(14)-C(13′), respectively. The distored ring C shows an enhanced reactivity in electrophilic substitution (halogenation, nitration, acetylation). The structure of 8, formed by addition during nitration of 1 using Cu(NO3)2/Ac2O, was established by spectroscopic methods. Maleic anhydride, dimethyl acetylenedicarboxylate, or benzyne easily react with the diene component 1 to give the Diels-Alder adducts 10-12. with oxygen 1 yields the endo peroxide 13.
    Notes: Die Röntgenstrukturanalyse von 7bH-Indeno[1,2,3-jk]fluoren (1) (Raumgruppe rhombisch pnma; a = 8.298, b = 19.974, c = 7.368 Å; z = 8/2) zeigt, daß sich die 1 innewohnende Spannung vor allem in einer Deformation des Sechsringes C in Richtung auf eine unsymmetrische Wannen-form äußert: Die durch C(12), C(12′), C(13) und C(13′) aufgespannte Ebene bildet mit der Ebene durch C(12)-C(11)-C(12′) bzw. C(13)-C(14)-C(13′) einen Winkel von 16.3 bzw. 5.6°. Der deformierte Ring C weist bei der elektrophilen Substitution (Halogenierung, Nitrierung, Acetylierung) erhöhte Reaktivität auf. Die Struktur eines bei der Nitrierung von 1 mit Cu(NO3)2/Ac2O gebildeten Additionsprodukts 8 wird mit Hilfe spektroskopischer Methoden aufgeklärt. 1 setzt sich als Dien-Komponente glatt mit Maleinsäureanhydrid, Acetylendicarbonsäure-dimethylester oder Dehydrobenzol zu den Diels-Alder-Addukten 10-12 um. Mit Sauerstoff liefert 1 das endo-Peroxid 13.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19751080605
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  • 5
    Electronic Resource
    Electronic Resource
    Die Kristallstruktur des 1,1,3,3-Bis(2,2′-biphenylylen)propens und des Lithium-1,1,3,3-bis(2,2′-biphenylylen)propenid-Monodiethylethers (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 3920-3929 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The Crystal Structure of 1,1,3,3-Bis(2,2′-biphenylylene)propene and Lithium-1,1,3,3-bis(2,2′-biphenylylene)propenide-DiethyletherThe molecular structure of the title compounds have been determined by X-ray structure analysis and refined to R=0.064 and 0.046, respectively. In the hydrocarbon 1 the twist angle between the two planar fluorene systems is 81°. In the lithium compound 2 the two identical fluorene units show distinct deviations from planarity (fig.5) and are distorted by 46°. The coordination sphere of each lithium atom consists of two rings A from different carbanion molecules (lithium ring distance=2.42 Å) and one ether oxygen atom (Li—O=1.91 Å), arranged in an approximate planar trigonal configuration. The structure of 2 is interpreted in terms of covalent interaction of lithium sp2 orbitals with the π cloud of the carbanion and of the lithium p orbital with the HOMO of the carbanion as previously described in other cases.
    Notes: Die Molekülstruktur der Titelverbindungen wurde durch Röntgenstrukturanalyse bestimmt und bis zu einem R-Wert von 0.046 bzw. 0.064 verfeinert. Im Kohlenwasserstoff 1 sind die beiden planaren Fluorensysteme um 81° gegeneinander verdrillt. In der Lithiumverbindung 2 bilden die beiden identischen Fluoren-Einheiten, welche deutliche Abweichungen von einem planaren Bau aufweisen (Abb. 5), miteinander einen Winkel von 46°. Die Koordinatiossphäre der Lithiumatome umfaßt die Ringe A aus verschiedenen Carbanion-Molekülen (Lithium-Ring-Abstand=2.42 Å) und ein Ethersauerstoff-Atom (Li — O=1.91 Å), die angenähert trigonal planar angeordnet sind. Die Struktur von 2 wird wie bereits früher in anderen Fällen über eine kovalente Wechselwirkung der sp2-Orbitale des Lithiums mit der π-Elektronenwolke sowie des p-Orbitals des Lithiums mit dem HOMO des Carbanios interpretiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771101223
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  • 6
    Electronic Resource
    Electronic Resource
    Lithium-7bH-indeno[1,2,3-jk]fluorenid, eine Organolithiumverbindung mit „Sandwich“-StrukturGespannte alkyl-aromatische Systeme, 4. Mitteilung. Diese Arbeit wurde vom Fonds der Chemischen Industrie unterstützt. - 3. Mitteilung: P. Luger, Ch. Tuchscherer, M. Große, D. Rewicki, Chem. Ber. 109, 2596 (1976). (1977)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 89 (1977), S. 490-491 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19770890723
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  • 7
    Electronic Resource
    Electronic Resource
    Lithium 7bH-Indeno [1,2,3-jk] fluorenide, an Organolithium Compound Having a “Sandwich” StructureStrained Alkyl-Aromatic Systems, Part 4. This work was supported by the Fonds der Chemischen Industrie. - Part 3: P. Luger, Ch. Tuchscherer, M. Grosse, D. Rewicki, Chem. Ber. 109, 2596 (1976). (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 16 (1977), S. 474-475 
    Details
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.197704741
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