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  • General Chemistry  (80)
  • Structure  (6)
  • in situ hybridization  (5)
  • 1995-1999  (82)
  • 1920-1924  (9)
  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1353-1360 
    ISSN: 1434-193X
    Schlagwort(e): Heterocycles ; Substitution ; Carbohydrates ; Anomeric O-hetarylation ; Glycosylation ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Anomeric O-hetarylation of tetra-O-benzyl- and tetra-O-acetylglucose (1a, b) can be directly performed with electron-deficient heteroaromatic/heterocyclic systems 2-14, which contain imide halide moieties. The reactions were carried out in the presence of a base and led, through an exchange of the halide by the glucopyranosyloxy moiety, to the products 2a-14a, 7b-14b. Predominantly or exclusively β-products were obtained. Systems bearing more than one imide halide moiety, such as cyanuric fluoride (15) or 5-chloro-2,4,6-trifluoropyrimidine (16), can be employed for successive anomeric O-hetarylations. Investigation of the glycosyl donor properties of O-glucosyl heteroaromatic imidates with 6-O- and 4-O-unprotected glucose derivatives 18 and 19 as acceptors and comparison of the results obtained with data for the corresponding β-trichloroacetimidates 17aβ and 17bβ, reveals that 2,3,5,6-tetrafluoropyridin-4-yl glucopyranosides 14aβ and 14bβ exhibit similar properties. For specific tasks, for instance α-glucopyranoside formation, 14aβ may even be advantageous.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 127 (1996), S. 1215-1220 
    ISSN: 1434-4475
    Schlagwort(e): Coordination of As(III) ; Structure ; Stereoisomeres
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Summary Arsenictris(trifluoroacetate) (1) crystallizes monoclinic in the space group Cc witha=1229.3,b=1697.9,c=1243.5 pm, β=110.01°, andZ=8. The trifluoroacetic acid ions acts as chelating ligands. Additionally they are bridging crystallographic independent molecules. As has a coordination number of 3+3(+2). The unit cell contains two sets of chirameres.
    Notizen: Zusammenfassung Arsen-tris(trifluoracetat) (1) kristallisiert monoklin in der Raumgruppe Cc mita=1229.3,b=1697.9,c=1243.5 pm, β=110.01° undZ=8. Die Trifluoracetatanionen fungieren gegenüber As als zweizähnige Liganden und verknüpfen die beiden kristallographisch unabhängigen Moleküle zusätzlich intermolekular. As erreicht dadurch gegenüber O die Koordinationszahl 3+3(+2). Die Elementarzelle enthält zwei Sätze von chirameren Molekülen.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 126 (1995), S. 1045-1050 
    ISSN: 1434-4475
    Schlagwort(e): Coordination of Sb(III) ; Structure ; Enantiomers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Summary The Δ isomer of (C6H5CO2)3Sb crystallizes rhombohedrally (hexagonal axes) in the space group R3 witha=1944.0 pm,c=422.3 pm, andZ=3. The molecules are stacked parallel to 001; Sb has a coordination number of 3+3 (Sb-O: 208 and 256 pm, resp.).
    Notizen: Zusammenfassung Das Δ-Isomer des Antimontribenzoats kristallisiert rhomboedrisch (hexagonale Aufstellung) in der Raumgruppe R3 mita=1944.0 pm,c=422.3 pm undZ=3. Die Moleküle sind parallel zu 001 gestapelt. Sb hat gegenüber O die Koordinationszahl 3+3 (Sb-O: 208 bzw. 256 pm).
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 127 (1996), S. 461-468 
    ISSN: 1434-4475
    Schlagwort(e): Coordination of As(III) and Sb(III) ; Structure ; Enantiomers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Summary Arsen-tris(2,2-dimethylpropionate) (1) crystallizes monoclinic in the space group P21/n witha=926.2,b=2158.6,c=983.7 pm, β=94.92°, andZ=4. As has a coordination number of 3+3. Antimony tripropionate (2) crystallizes monoclinic in the space group P21/c witha=930.2,b=863.0,c=1575.2 pm, β=90.27, andZ=4. The molecules are bridged to chains; therefore, Sb reaches the coordination number 3+3 (+3).
    Notizen: Zusammenfassung Arsen-tris(2,2-dimethylpropionat) (1) kristallisiert monoklin in der Raumgruppe P21/n mita=926.2,b=2158.6,c=983.7 pm, β=94.92° undZ=4. As hat gegenüber O die Koordinationszahl 3+3. Antimontripropionat (2) kristallisiert monoklin in der Raumgruppe P21/c mita=930.2,b=863.0,c=1575.2 pm, β=90.27 undZ=4. Die Moleküle sind intermolekular zu Ketten verknüpft, wodurch Sb die Koordinationszahl 3+3 (+3) erreicht.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 1573-5028
    Schlagwort(e): Beta procumbens ; Beta vulgaris ; in situ hybridization ; repetitive DNA ; satellite DNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Members of three prominent DNA families of Beta procumbens have been isolated as Sau3A repeats. Two families consisting of repeats of about 158 bp and 312 bp are organized as satellite DNAs (Sau3A satellites I and II), whereas the third family with a repeat length of 202 bp is interspersed throughout the genome. Multi-colour fluorescence in situ hybridization was used for physical mapping of the DNA families, and has shown that these tandemly organized families occur in large heterochromatic and DAPI positive blocks. The Sau3A satellite I hybridized exclusively around or near the centromeres of 10, 11 or 12 chromosomes. The Sau3A satellite family I showed high intraspecific variability and high-resolution physical mapping was performed on pachytene chromosomes using differentially labelled repeats. The physical order of satellite subfamily arrays along a chromosome was visualized and provided evidence that large arrays of plant satellite repeats are not contiguous and consist of distinct subfamily domains. Re-hybridization of a heterologous rRNA probe to mitotic metaphase chromosomes revealed that the 18S-5.8S-25S rRNA genes are located at subterminal position on one chromosome pair missing repeat clusters of the Sau3A satellite family I. It is known that arrays of Sau3A satellite I repeats are tightly linked to a nematode (Heterodera schachtii) resistance gene and our results show that the gene might be located close to the centromere. Large arrays of the Sau3A satellite II were found in centromeric regions of 16 chromosomes and, in addition, a considerable interspersion of repeats over all chromosomes was observed. The family of interspersed 202 bp repeats is uniformly distributed over all chromosomes and largely excluded from the rRNA gene cluster but shows local amplification in some regions. Southern hybridization has shown that all three families are specific for genomes of the section Procumbentes of the genus Beta.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1573-5028
    Schlagwort(e): Arabidopsis thaliana ; ferns ; in situ hybridization ; phylogenetics ; pines ; reverse transcriptase genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have investigated the physical distribution of the reverse transcriptase genes of Ty1-copia-like retrotransposable elements from 12 plant species belonging to different subdivisions by hybridization in situ on chromosome preparations. Ty1-copia-like elements showed different and non-random hybridization patterns. A dispersed distribution throughout most of the chromosomes with reduced hybridization at some regions or with some weak clustering at other regions was found in Allium cepa, Beta vulgaris, Brassica campestris, Brassica oleracea, Pennisetum glaucum, Pinus elliottii, Selaginella apoda, Vicia faba and Vicia narbonensis. Reduced hybridization occured mainly at centromeric regions, nucleolus-organizing regions and regions known to be mainly composed of tandemly repeated sequences. In the fern Pteris cretica the retroelements showed a dispersed genomic organization with clustering at some chromosomal regions and whole chromosomes showing little signal. In Arabidopsis thaliana and Cicer arietinum, Ty1-copia-like elements were found in clusters at the paracentromeric heterochromatin, a novel organization for a repetitive element in A. thaliana. New retroelement families were isolated from A. thaliana and from Beta vulgaris. Alignment of the deduced peptide sequences with Ty1-copia-like elements from other plants showed considerable divergence which was used to calculate their relationships, indicating the value of reverse transcriptase gene analysis in phylogenetic and biodiversity studies.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    ISSN: 1573-5028
    Schlagwort(e): Arabidopsis arenosa ; Cruciferae ; genus Arabidopsis ; in situ hybridization ; molecular systematics ; satellite DNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have analysed a family of highly repetitive DNA from Arabidopsis arenosa (L.) Lawalrée [syn. Cardaminopsis arenosa (L.) Hayck] composed of AT-rich tandem repeats of 166–179 bp in head to tail organization. Sequence comparison between several repeat units revealed a high level of divergence of 4.5% to 25%. The sequence family shows more than 58% homology to satellite sequences described in Arabidopsis thallana (L.) Heynh. but no homology to other satellite repeats in the Cruciferae. Within the genus Arabidopsis the satellite sequence was found to be present in A. thaliana and Arabidopsis suecica (Fries) Norrlin, but not in Arabidopsis griffithiana (Boiss.) N. Busch and Arabidopsis pumila (Stephan) N. Busch. In situ hybridization to metaphase chromosomes of A. arenosa (2n=4x=32) showed the sequence to be localized at the centromeres of all 32 chromosomes with substantial hybridization along the chromosome arms. Using Southern hybridization and in situ hybridization, we give evidence that A. suecica is a hybrid of A. thaliana and A. arenosa. A considerable reorganization of the A. thaliana satellite sequence pAL1 occurred in the hybrid genome while no molecular change of the A. arenosa repeat was observed in the hybrid. Analysis of related repeats enabled differentiation between closely related genomes and are useful for the investigation of hybrid genomes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1573-6849
    Schlagwort(e): Beta vulgaris ; in situ hybridization ; LINE ; LTR retrotransposons ; non-LTR (non-viral) retrotransposons ; Ty1-copia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract DNA sequences of the reverse transcriptase gene of long terminal repeat (LTR) and non-LTR (non-viral) retrotransposons have been isolated and cloned from the genome of sugar beet (Beta vulgaris). Both retrotransposon types are highly amplified in sugar beet and may account for 2–5% of the genome. The BNR1 family, representing the first non-viral retrotransposon reported from a dicotyledonous species, shows homology to the mammalian L1 family of long interspersed repeated sequences (LINEs) and to retrotransposable elements from maize and lily. Sequences of the Tbv family are homologous to theTy1-copia class of LTR retrotransposons. The BNR1 and Tbv retrotransposon families are characterized by sequence heterogeneity and are probably defective. The deduced peptide sequences were used to investigate the relation to other retroelements from plants, insects and mammals. Fluorescencein situ hybridization was used to investigate the physical distribution and revealed that both retrotransposon families are present on all sugar beet chromosomes and largely excluded from chromosomal regions harbouring the 18S–5.8S–25S rRNA genes. The BNR1 family is organized in discrete clusters, while the Tbv family ofTy1-copia-like retrotransposons shows a more uniform distribution along chromosome arms and is absent from some chromosomal regions. These contrasting distributions emphasize the differences in evolutionary amplification and dispersion mechanisms between the two types of retrotransposons. Thein situ results of both elements reflect significant features of a higher order structure of the genome, as it is known for both short interspersed repeated sequences (SINEs) and LINEs in human.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1573-5028
    Schlagwort(e): sugar beet (Beta vulgaris) ; LINEs ; non-LTR retrotransposons ; reverse transcriptase gene ; in situ hybridization ; genome organization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have isolated and characterized conserved regions of the reverse transcriptase gene from non-LTR retrotransposons, also called long interspersed nuclear elements (LINEs), from Beta vulgaris, B. lomatogona and B. nana. The novel elements show strong homology to other non-LTR retrotransposons from plants, man and animals. LINEs are present in all species of the genus Beta tested, but there was variation in copy number. Analysis by Southern hybridization and fluorescent in situ hybridization revealed the clustered organization of these retroelements in beet species. PCR amplification using degenerate primers to conserved motifs of the predicted LINE protein sequence enabled the cloning of LINEs from both Monocotyledonae (Allium cepa, Oryza sativa and Secale cereale) and Dicotyledonae (Nicotiana tabacum and Antirrhinum majus) indicating that LINEs are a universal feature of plant genomes. A dendrogram of fifteen new and six previously isolated sequences showed the high level of sequence divergence while revealing families characteristic of some genera. The genomic organization of non-LTR retrotransposons was examined more detailed in A. majus and O. sativa.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2409-2416 
    ISSN: 1434-193X
    Schlagwort(e): Sulfur heterocycles ; Rearrangements ; Reductions ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The syntheses of 1,2-benzodithiino[5,4,3-cde][1,2]benzodithiin-2,7-diamine (1) and dithio-bridged benzidine 2 have been achieved. The starting material for the synthesis of 1 was 1,3-diiodo-5-nitrobenzene (15) which was transformed by conventional means into 1,2-bis[3,5-bis(ethylthio)phenyl]diazane (19). The benzidine rearrangement of 19 in the presence of HBF4 at -30 °C yielded 4,4′-diamino-2,2′,6,6′-tetraethylthiobiphenyl (20) in 50 % yield. Treatment of 20 with sodium in ammonia and work-up in the presence of air yielded 1. The latter compound could be reduced with LiAlH4 to the tetrathiol 20a. The starting material for the preparation of 2 was 3-chloro-1-iodo-5-nitrobenzene (23), a side product of the preparation of 15. It was transformed analogously to the preparation of 1 into 1,2-bis(3-ethylthiophenyl)diazane (28). The benzidine rearrangement of 28 in presence of HBF4 at -30 °C afforded 4,4′-diamino-2,2′-bis(ethylthio)biphenyl (29) in 49 % yield. Treatment of 29 with sodium in ammonia and work-up under aerobic conditions yielded 2. Quantitative reduction of 2 to the thiol 29a could be achieved with LiAlH4. The reversible electrochemical reduction of 1 on unmodified glassy carbon electrodes leads to a product to which the structure of 3 was assigned.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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