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  • Chemistry  (2)
  • Chaperone  (1)
  • General Chemistry
  • Condensed Matter: Electronic Properties, etc.
  • 1995-1999  (3)
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  • 1
    ISSN: 1432-2048
    Keywords: Chaperone ; Chloroplasts ; Chromoplasts ; Heat-shock protein ; Secale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A partial cDNA which codes for the β-subunit of a plastidic chaperonin 60 (cpn60-β) from rye (Secale cereale L.) leaves was identified and sequenced, except for 46 amino acids of the N-terminus of the mature protein and the transit sequence. This is the first cpn60-β sequence determined for a monocotyledonous plant. Specific antibodies against cpn60-β were affinity-purified from an antiserum raised against the total soluble protein fraction of ribosome-deficient plastids. The localization of cpn60-β in chloroplasts or non-green plastids was confirmed by immunodetection in Percoll gradient-purified organelles. The expression and occurrence of cpn60-β was analysed by immunoblotting with the specific antibodies and Northern hybridization. The cpn60-β protein was constitutively expressed in various green and non-green tissues. It was evenly distributed along the major part of a rye leaf, while highest transcript levels occurred in the youngest and oldest leaf sections. The expression of the cpn60-β protein was not enhanced by a heat-shock treatment at 42 °C. The cpn60-β transcript and protein were more strongly expressed in various non-green, for instance etiolated, 70S-ribosome-deficient 32 °C-grown, or herbicide-bleached tissues, than in green leaves of rye. A rapid increase in the cpn60-β transcript level was also observed when green leaves were transferred from light to darkness while the protein level was not affected. The dark-induced increase in the cpn60-β transcript was totally suppressed in the presence of 2% sucrose. Inhibitor treatments suggested that the change in cpn60-β transcript level was not related to changes of the ATP supply of the tissue. While the large subunit of the photosynthetic protein ribulose-1,5-bisphosphate carboxylase was largely degraded during ripening of tomato fruits, high levels of cpn60-β were detected in tomato chromoplasts and in the yellow flower petals of Narcissus. Low levels of cpn60-β were detected in root tissue.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0044-2313
    Keywords: 1,2-Diphospha-3,4-diboretanes ; 1,3-diphospha-2,4,5-triborolane derivative ; preparation ; molecular structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2-Diphospha-3,4-diboretanes and 1,3-Diphospha-2,4,5-triborolane: Synthesis and Structure as well as Calculations on the Molecular Structure On the Effect of Substituents on the Structure of 1,2-Diphospha-3,4-diboretane[2 + 2]-Cyclocondensation reactions led to the synthesis of the 1,2-diphospha-3,4-diboretanes [(t-BuP)2B2(NMe2)2], 1 a, and [(t-BuP)2B(NMe2)B(NiPr2)], 1 b. Their molecular structures have been determined by X-ray methods, and these are compared with the structure of [(t-Bu)P—BN(iPr2)]2, 2 a. Compounds 1 show a folded B2P2 four membered ring having tert.-butyl groups in anti-positions. Ab initio calculations on 1,2-diphospha-3,4-diboretanes demonstrate that two conformers with anti-orientation of the substituents at the phosphorus atoms can be expected. These differ by the relative orientation of the almost planar P2BR groups to the BP2 plane. The influence of substituents (H and NH2 at the B atoms, and H and Me at the P atoms) on the ring conformation has been studied. Finally, the first derivative of a 1,3-diphospha-2,4,5-triborolane, 3 a, is reported.
    Notes: Durch [2 + 2]-Cyclokondensationen wurden die 1,2-Diphospha-3,4-diboretane [(t-BuP)2B2(NMe2)2], 1 a, und [(t-BuP)2B(NMe2)B(NiPr2)], 1 b, dargestellt, ihre Molekülstrukturen mit Röntgenbeugungsmethoden bestimmt und mit der Struktur von [(t-Bu)P—B(NiPr2)]2, 2 a, verglichen. In den Verbindungen 1 liegen gefaltete B2P2-Vierringe vor mit anti-ständigen tert.-Butylgruppen, während das Ringsystem in 2 a planar gebaut ist, die tert.-Butylgruppen aber ebenfalls anti-Stellung einnehmen. Ab initio-Rechnungen an 1,2-Diphospha-3,4-diboretanen belegen, daß zwei unterschiedliche Konformere mit anti-Orientierung der Substituenten an den P-Atomen stabil sind, die sich durch die relative Orientierung der annähernd trigonal-planaren P2BR-Baugruppen zur BP2-Ebene voneinander unterscheiden. Der Einfluß von Substituenten (H und NH2 am B-Atom, H und CH3 am P-Atom) wird ermittelt. Beschrieben wird ferner das erste Derivat eines 1,3-Diphospha-2,4,5-triborolans, 3 a.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1945-1953 
    ISSN: 0044-2313
    Keywords: Bismutoxideiodides ; totale pressure measurements ; mass spectrometry ; thermodynamic data ; melting diagram ; barogram ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on the System Bi2O3/BiI3The temperature functions of decomposition pressures of the ternary compounds on the quasibinary line Bi2O3/BiI3 were determined by total pressure measurements and mass spectrometry. The barogram of the system was constructed and the melting diagram precised. The enthalpies of formation and the standard entropies of the solid phases were derived from the decomposition functions: (Values see Inhaltsübersicht).
    Notes: Die Temperaturabhängigkeit der Zersetzungsdrücke der auf dem quasibinären Schnitt Bi2O3/BiI3 existierenden ternären Verbindungen wurde durch Gesamtdruckmessungen mit dem Membrannullmanometer und dem Massenspektrometer ermittelt. Das Zustandsbarogramm für das System wurde aufgestellt und das Zustandsdiagramm präzisiert. Unter Zugrundelegung der Zersetzungsgleichungen wurden die Standardbildungsenthalpien und Standardentropien der festen ternären Phasen hergeleitet: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm BiOI, f, 298) = - 268,1} \pm {\rm 6,3}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm BiOI, f, 298) = 116,9} \pm {\rm 7,1}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 4} {\rm O}_{\rm 5} {\rm I}_{\rm 2} {\rm, f, 298) = - 1148,8} \pm 20{\rm,9}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 4} {\rm O}_{\rm 5} {\rm I}_{\rm 2} {\rm, f, 298) = 367,1} \pm 25{\rm,1}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 7} {\rm O}_{\rm 9} {\rm I}_{\rm 3} {\rm, f, 298) = - 2022,5} \pm 34{\rm,3}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 7} {\rm O}_{\rm 9} {\rm I}_{\rm 3} {\rm, f, 298) = 619,8} \pm 41{\rm,0}\,\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \Delta {\rm H}_{\rm B}^{\rm o} \,({\rm Bi}_{\rm 5} {\rm O}_{\rm 7} {\rm I, f, 298) = - 1471,2} \pm 20{\rm,1}\,{\rm kJ}\,{\rm mol}^{{\rm - 1}} \\ {\rm S}^ \circ \,({\rm Bi}_{\rm 5} {\rm O}_{\rm 7} {\rm I, f, 298) = 385,3} \pm 24{\rm,3}\,{\rm J}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} \\ \end{array} $$\end{document}.
    Additional Material: 6 Ill.
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