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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of cluster science 5 (1994), S. 173-184 
    ISSN: 1572-8862
    Keywords: Rhenium ; dimetal comptexes ; phosphine ligands ; carboxylatebridged complexes ; redox chemistry ; preparation ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reactions of the quadruply bonded dirhenium(III) carboxylatescis-Re2(μ-O2CR)2X4L2 (X=CI or Br; L=a monodentate donor) with monodentate, bidentate, and tridentate phosphine donors result in several types of redox behavior, usually involving partial or complete reductive decarboxylation of the dirhenium unit. Examples of dirhenium(VI, II), dirhenium(IV, II), dirhenium(III, II), and dirhenium(II, II) complexes, in which Re-Re bond orders of 4, 3.5, 3, l, or zero are encountered, have been isolated and repre-sentative examples structurally characterized. The course of these reactions is dependent upon the nature of the phosphine. The scope of this remarkably rich chemistry is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8862
    Keywords: Rhenium ; clusters ; hydrido-bridged ; hydrosulfido-bridged ; preparation ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reactions of Re2X4(μ-dppm)2 (X=Cl or Br; dppm=Ph2PCH2PPh2) with H2S in THF afford the dirhenium (III) complexes Re2(μ-H)(μ-SH)X4(μ-dppm)2, the first examples of the oxidative addition of an S-H unit across an electron-rich metal-metal triple bond. The bromide complex Re2(μ-H)(μ-SH)Br4(μ-dppm)2 (C2H5)2O crystallizes in the space group P21/n witha=16.631(2) Å,b=15.967(3) Å,c=19.904(2) Å, β=92.698(7)°,V=5279(2) Å3, andZ=4. The structure which was refined toR=0.053 (R w=0.070) for 4903 data withI〉3.0σ(I), shows the presence of an edge-shared bioctahedral geometry with a very short Re-Re distance of 2.4566(7) Å. While the hydrogen atoms of the μ-H and μ-SH ligands were not located in the X-ray structure determination, their presence is confirmed by IR and1H NMR spectroscopy.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8862
    Keywords: Rhenium ; dimetal clusters ; hydrido-complexes ; phosphidobridged ; preparation ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Diphenylphosphine oxidatively adds to the Re≡Re bonds of Re2 X 4(μ-dppm)2 (X=Cl or Br; dppm=Ph2PCH2PPh2) and Re2Cl4(μ-dpam)2 (dpam=Ph2AsCH2AsPh2) to afford the dirhenium(III) complexes Re2(μ-X)(μ-PPh2)HX 3(μ-LL)2. The dppm complexes have also been prepared from the reactions of Re2(μ-O2CCH3)X 4(μ-dppm)2 with Ph2PH, and a similar strategy has been used to prepare Re2(μ-Cl)(μ-PPh2)HCl3(μ-dmpm)2 (dmpm=Me2PCH2PMe2) from Re2(μ-O2CCH3)Cl4(dmpm)2. Phenylphosphine likewise reacts with Re2 X 4(μ-dppm)2 to give Re2(μ-X)(μ-PHPh)HX 3(μ-dppm)2. An X-ray crystal structure determination on Re2(μ-Cl)(μ-PPh2)HCl3(μ-dppm)2 confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group $$R\bar 3$$ (No. 148) witha=21.699(3) Å, α=84.50(4)°,V=10084(5) Å3, andZ=6. The structure was refined toR=0.049 (R w 0.069) for 5770 data withI〉3.0σ(I). The Re-Re distance is 2.5918(7) Å. Oxidation of the bromide complex Re2(μ-Br)(μ-PPh2)HBr3(μ-dppm)2 with NOPF6 produces the unusual dirhenium(III, II) cation [Re2(μ-H)(μ-Br)[P(O)Ph2]Br2(NO)(μ-dppm)2]+ which has been structurally characterized as its perrhenate salt, [Re2(μ-H)(μ-Br)[P(O)Ph2]Br2(NO)(μ-dppm)2]ReO4 · 2CH2Cl2. This complex crystallizes in the space group $$P\bar 1$$ (No. 2) witha=14.187(7) Å,b=16.419(5) Å,c=16.729(5) Å, α=98.76(2)°, β=110.11(3)°, γ=104.66(3)°,V=3414(6) Å3,Z=2. The structure was refined toR=0.040 (R w =0.051) for 5736 data withI〉3.0σ(I). The presence of a phosphorus-bound [P(O)Ph2]− ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) Å.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0749-503X
    Keywords: Peroxisomes ; protein tarageting ; Saccharomyces cerevisiae ; Candida tropicalis ; Candida albicans ; Yarrowia lipolytica ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The carboxyl-terminal tripeptide Ala-Lys-Ile is essential for targeting Canadida tropicalis trifunctional enzyme (hydratase-dehydrogenase-epimerase) to peroxisomes of both Candida albicans and Saccharomyces cerevisiae (Aitchison, J. D., Murray, W. W. and Rachubinski, R. A. (1991). J. Biol. Chem. 266, 23197-23203). We investigated the possibility that this tripeptide may act as a general peroxisomal targeting signal (PTS) for other proteins in the yeasts C. tropicalis, C. albicans, Yarrowia lipolytica and S. cerevisiae, and in rat liver. Anti-AKI antibodies raised against the carboxyl-terminal 12 amino acids of trifunctional enzyme were used to search for this PTS in proteins of these yeasts and of rat liver. The anti-AKI antibodies reacted exclusively with multiple peroxisomal proteins from the yeasts C. tropicalis, C. albicans and Y. lipolytica. There was a weak reaction of the antibodies with one peroxisomal protein from S. cerevisiae and no reaction with peroxisomal proteins from rat liver. Antibodies directed against a synthetic peptide containing a carboxyl-terminal Ser-Lys-Leu PTS (Gould, S. J., Krisans, S., Keller, G.-A. and Subramani, S. (1990). J. Cell Biol. 110, 27-34) reacted with multiple peroxisomal proteins of rat liver and with peroxisomal proteins of yeast distinct from those identified with anti-AKI antibodies. These results provide evidence that several peroxisomal proteins of different yeasts contain a PTS antigenically similar to that of C. tropicalis trifunctional enzyme and that this signal is absent from peroxisomal proteins from at least one mammalian system, rat liver.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0749-503X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The Saccharomyces cerevisiae RNA polymerase II subunit gene RPB7 was isolated and sequenced. RPB7 is a single copy gene whose sequence predicts a 19,000 Dalton protein of 171 amino acids. RPB7 is known to dissociate from RNA polymerase II as an RPB4/RPB7 subcomplex in vitro. RPB7 also appears to interact with RNA polymerase II in a manner dependent upon RPB4, since RNA polymerase II purified from cells lacking RPB4 also lacks RPB7. Previous results have demonstrated that deletion of the RPB4 results in slow growth and cold- and temperature-sensitivity. In contrast, deletion of the RPB7 gene revealed that it is essential for cell growth and viability. Loss of both the RPB4 and the RPB7 genes causes lethality. These results suggest that RPB7 contributes to the function of RNA polymerase II in the absence of RPB4 either in a manner independent of its association with the enzyme or by directly binding to the enzyme in a manner independent of its association with RPB4.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 923-927 
    ISSN: 0749-503X
    Keywords: ADP-ribosylation factors ; GTP-binding proteins ; Saccharomyces cerevisiae ; 3-amniotriazole ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A gene encoding a homologue of the ADP-ribosylation factor (ARF) family of small GTP binding proteins was cloned from a Schizosaccharomyces pombe cDNA library by a functional screen of suppressors of sensitivity to 3-aminotriazole in a gcn3 null strain of Saccharomyces cerevisiae. Two independent isolates each contained the full coding region of the ARF1 gene. The encoded SpARF1 protein has a predicted molecular weight of 20 618 and is 88% and 79% identical to human and S. cerevisiae ARF1 proteins, respectively. As independent isolates were obtained, this effect of the SpARF1 appears to be a real phenomenon, but cannot currently be easily understood within the context of the evidence for a role(s) for ARF proteins in the protein secretory pathway.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0749-503X
    Keywords: Peroxisome ; immunofluorescence ; PTS-1 ; electroporation ; yeast ; targeting ; biogenesis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We describe the isolation and characterization of peroxisomal assembly mutants in the genetically manipulable yeast Yarrowia lipolytica (pay mutants). These mutants were initially identified as oleic acid-non-utilizers by their inability to grow on oleic acid, the utilization of which requires peroxisomal β-oxidation enzymes. Identification of a subset of oleic acid-non-utilizers as pay mutants was obtained by a rapid immunofluorescence procedure using antibodies to the peroxisomal targeting signal Ser-Lys-Leu-CO2H. Punctate structures characteristic of peroxisomes were not detected in pay mutants using this technique. This rapid identification by immunofluorescence should be generally applicable to the selection of peroxisomal assembly mutants in other yeasts. To take advantage of the pay mutant system, we constructed a genomic library in the autonomously replicating vector pINA445 and developed an efficient and rapid electroporation procedure for the functional complementation of these mutants. We have been successful in functionally complementing two independent pay mutants. Molecular analysis of these and other complementing genes will allow for characterization of some of the cellular elements involved in peroxisomal assembly.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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