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  • 1990-1994  (6)
  • Medicago sativa L.  (3)
  • Rhenium  (3)
  • 1
    Digitale Medien
    Digitale Medien
    The quadruply bondedbis-carboxylatescis-Re2(μ-O2CCH3)2X4L2 (X = halide;L = neutral donor) as synthons in dirhenium chemistry (1994)
    Springer
    Journal of cluster science 5 (1994), S. 173-184 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Rhenium ; dimetal comptexes ; phosphine ligands ; carboxylatebridged complexes ; redox chemistry ; preparation ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01165498
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  • 2
    Digitale Medien
    Digitale Medien
    The oxidative addition of hydrogen sulfide to the electron-rich triple bond: The isolation and characterization of compounds that contain the Re2(μ-H)(μ-SH) cluster unit (1991)
    Springer
    Journal of cluster science 2 (1991), S. 259-270 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Rhenium ; clusters ; hydrido-bridged ; hydrosulfido-bridged ; preparation ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00702956
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  • 3
    Digitale Medien
    Digitale Medien
    The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(μ-X)(μ-PR2)Re cluster (X=halide) (1992)
    Springer
    Journal of cluster science 3 (1992), S. 83-102 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Rhenium ; dimetal clusters ; hydrido-complexes ; phosphidobridged ; preparation ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00814613
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  • 4
    Digitale Medien
    Digitale Medien
    Molecular characterization and expression of an isocitrate dehydrogenase from alfalfa (Medicago sativa L.) (1992)
    Springer
    Plant molecular biology 20 (1992), S. 801-807 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Medicago sativa L. ; cell suspension culture ; isocitrate dehydrogenase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A putative isocitrate dehydrogenase (IDH) cDNA from alfalfa has been cloned and sequenced. The derived amino acid sequence of 433 residues contains the isocitrate and isopropylmalate dehydrogenase signatures, is 63% identical to yeast mitochondrial NADP-IDH and shares high sequence identity with peptides of pig heart NADP-IDH. The sequence contains a potential N-terminal leader with similarities to a thylakoid transit peptide. IDH transcripts and NADP-IDH activity were detected in all alfalfa tissues examined, their levels depending upon the tissue type and its developmental stage. Transcripts and enzymatic activity were not induced on exposure of cell suspension cultures to a fungal elicitor. IDH is encoded by a small gene family in alfalfa.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00027151
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  • 5
    Digitale Medien
    Digitale Medien
    Stress responses in alfalfa (Medicago sativa L.) III. Induction of medicarpin and cytochrome P450 enzyme activities in elicitor-treated cell suspension cultures and protoplasts (1990)
    Springer
    Plant cell reports 9 (1990), S. 38-41 
    Details
    ISSN: 1432-203X
    Schlagwort(e): Medicago sativa L. ; Cytochrome P450 ; Elicitor ; Phytoalexin ; Protoplasts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Cell suspension cultures of alfalfa (Medicago sativa L.) accumulated phenolic secondary metabolites in a pattern similar to that seen in alfalfa roots. Upon treatment with a crude elicitor preparation from the bean pathogen Colletotrichum lindemuthianum, the pterocarpan phytoalexin medicarpin accumulated in cells and culture medium. The extractable activities of six enzymes involved in medicarpin biosynthesis (including three cytochrome P450 activities) were induced by treatment with elicitor, and their induction kinetics correlated with the rate of medicarpin accumulation. However, protoplasts prepared from these cultures accumulated neither medicarpin nor other secondary products after treatment with elicitor. The cytochrome P450 activities were induced during the preparation of the protoplasts, but could be further induced by treatment with fungal elicitor. The results are discussed in relation to the use of alfalfa protoplasts as a system for functional analysis of cloned defense genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00232132
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  • 6
    Digitale Medien
    Digitale Medien
    Stress responses in alfalfa (Medicago sativa L.) IV. Expression of defense gene constructs in electroporated suspension cell protoplasts (1990)
    Springer
    Plant cell reports 9 (1990), S. 42-46 
    Details
    ISSN: 1432-203X
    Schlagwort(e): Medicago sativa L. ; Protoplast ; Chalcone synthase ; Promoter ; Transient assay ; Antisense RNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary We have investigated conditions for the uptake and expression of chimeric genes in protoplasts of alfalfa (Medicago sativa L.). Constructs containing the bacterial reporter gene chloramphenicol acetyltransferase (CAT) under the control of either the cauliflower mosaic virus 35S promoter or a bean chalcone synthase (CHS) promoter were introduced into protoplasts by electroporation in the presence of polyethyleneglycol. The extent of expression in the absence of added inducers depended on the conditions for isolation, electroporation and subsequent culture of the protoplasts. Expression of the CHS promoter construct was increased on exposure of the protoplasts to a fungal elicitor or reduced glutathione. The relative levels of induced expression in relation to either basal expression or the type of elicitor used depended on the age of the suspension cultures from which the protoplasts were isolated. Electroporation of protoplasts with a construct from which bean CHS antisense transcripts were synthesized under the control of the 35S promoter resulted in the inhibition of appearance of elicitor-induced endogenous alfalfa CHS activity. The suitability of the alfalfa protoplast system for analysis and potential identification of defense response genes is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00232133
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