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  • Protein phosphorylation  (6)
  • Inorganic Chemistry  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Diurnal modulation of phosphoenolpyruvate carboxylation in pea leaves and roots as related to tissue malate concentrations and to the nitrogen source (1996)
    Springer
    Planta 198 (1996), S. 495-501 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium ; Malate ; Nitrate ; Phosphoenolpyruvate carboxylase ; Protein phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoenolpyruvate (PEP) carboxylation was measured as dark 14CO2 fixation in leaves and roots (in vivo) or as PEP carboxylase (PEPCase) activity in desalted leaf and roof extracts (in vitro) from Pisum sativum L. cv. Kleine Rheinländerin. Its relation to the malate content and to the nitrogen source (nitrate or ammonium) was investigated. In tissue from nitrate-grown plants, PEP carboxylation varied diurnally, showing an increase upon illumination and a decrease upon darkening. Diurnal variations in roots were much lower than in leaves. Fixation rates in leaves remained constantly low in continuous darkness or high in continuous light. Dark CO2 fixation of leaf slices also decreased when leaves were preilluminated for 1 h in CO2-free air, suggesting that the modulation of dark CO2 fixation was related to assimilate availability in leaves and roots. Phosphoenolpyruvate carboxylase activity was also measured in vitro. However, no difference in maximum enzyme activity was found in extracts from illuminated or darkened leaves, and the response to substrate and effectors (PEP, malate, glucose-6-phosphate, pH) was also identical. The serine/threonine protein kinase inhibitors K252b, H7 and staurosporine, and the protein phosphatase 2A inhibitors okadaic acid and cantharidin, fed through the leaf petiole, did not have the effects on dark CO2 fixation predicted by a regulatory system in which PEPCase is modulated via reversible protein phosphorylation. Therefore, it is suggested that the diurnal modulation of PEP carboxylation in vivo in leaves and roots of pea is not caused by protein phosphorylation, but rather by direct allosteric effects. Upon transfer of plants to ammonium-N or to an N-free nutrient solution, mean daily malate levels in leaves decreased drastically within 4–5 d. At that time, the diurnal oscillations of PEP carboxylation in vivo disappeared and rates remained at the high light-level. The coincidence of the two events suggests that PEPCase was de-regulated because malate levels became very low. The drastic decrease of leaf malate contents upon transfer of plants from nitrate to ammonium nutrition was apparently not caused by increased amino acid or protein synthesis, but probably by higher decarboxylation rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262634
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  • 2
    Electronic Resource
    Electronic Resource
    Acid-base-modulation of nitrate reductase in leaf tissues (1995)
    Springer
    Planta 196 (1995), S. 1-6 
    Details
    ISSN: 1432-2048
    Keywords: Acid-base loading ; Nitrate reductase ; pH regulation (intracellular) ; Protein phosphorylation ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of acid or base-loading of spinach (Spinacia oleracea L.) leaf discs on the activation status of nitrate reductase (NR) in the dark and in the light was investigated. Activity of NR (NRA), measured in crude extracts of leaf discs with removed lower epidermis, which had been floating on Mes-buffer [2-(N-morpholino)ethane sulfonic acid] pH 5.2 in the dark, was at a similar low level as in whole, darkened leaves. By addition of acetate or propionic acid, butyric acid or benzoic acid, NR was activated to or beyond the light level. The pH of crude tissue extracts was decreased by 0.5–1 pH units. Tissue acidification caused an inhibition of photosynthesis and of dark CO2 fixation. The acid-induced activation of NR in vivo was largely prevented by okadaic acid, an inhibitor of Type 1 and Type 2A protein phosphatases. This indicates that acid-induced activation was mediated by protein dephosphorylation. When, on the other hand, leaf discs were illuminated on Ches-buffer (2-[ N-cyclohexylamino]ethane sulfonic acid) pH 9 in the presence of bicarbonate (80 mM), their NR was as active as in intact leaves. Addition of ammonium chloride (up to 6 mM) caused a pH increase of the tissue extract up to 0.9 pH units. At the same time NR was inactivated to the dark level. Methionine sulfoximine did not prevent the ammonium effect. Photosynthesis and dark CO2 fixation were stimulated at pH 9 by ammonium chloride (1–2· mol· m −3) and were only slightly inhibited by up to 6 mol· m−3. The modulation of NR by acid-base treatment in vivo was fully reversible. The response of the NR system to acid or base treatment is consistent with a proposed role of nitrate reduction in the cellular pH-stat. The observation also indicates that cytosolic pH changes may be involved the signal chain triggering the modulation of NR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193210
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid modulation of nitrate reductase in pea roots (1993)
    Springer
    Planta 191 (1993), S. 173-179 
    Details
    ISSN: 1432-2048
    Keywords: Anaerobiosis ; Enzyme modulation ; Nitrate reductase ; Pisum ; Protein phosphorylation ; Root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The regulatory properties of nitrate reductase (NR; EC 1.6.6.1) in root extracts from hydroponically grown pea (Pisum sativum L. cv. Kleine Rheinländerin) plants were examined and compared with known properties of NR from spinach and pea leaves. Nitrate-reductase activity (NRA) extracted from pea roots decreased slowly when plants were kept in the dark, or when illuminated plants were detopped, with a half-time of about 4 h (= slow modulation in vivo). In contrast, the half-time for the dark-inactivation of NR from pea leaves was only 10 min. However, when root tip segments were transferred from aerobic to anaerobic conditions or vice versa, changes in NRA were as rapid as in leaves (= rapid modulation in vivo). Nitrate-reductase activity was low when extracted from roots kept in solutions flushed with air or pure oxygen, and high in nitrogen. Okadaic acid, a specific inhibitor of type-1 and type-2A protein phosphatases, totally prevented the in vivo activation by anaerobiosis of NR, indicating that rapid activation of root NR involved protein dephosphorylation. Under aerobic conditions, the low NRA in roots was also rapidly increased by incubating the roots with either uncouplers or mannose. Under these conditions, and also under anaerobiosis, ATP levels in roots were much lower than in aerated control roots. Thus, whenever ATP levels in roots were artificially decreased, NRA increased rapidly. The highly active NR extracted from anaerobic roots could be partially inactivated in vitro by preincubation of desalted root extracts with MgATP (2 mM), with a half-time of about 20 min. It was reactivated by subsequently incubating the extracts with excess AMP (2 mM). Thus, pea root NR shares many of the previously described properties of NR from spinach leaves, suggesting that the root enzyme, like the leaf enzyme, can be rapidly modulated, probably by reversible protein phosphorylation/ dephosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00199747
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  • 4
    Electronic Resource
    Electronic Resource
    Partial purification of two proteins (100 kDa and 67 kDa) cooperating in the ATP-dependent inactivation of spinach leaf nitrate reductase (1994)
    Springer
    Planta 192 (1994), S. 183-188 
    Details
    ISSN: 1432-2048
    Keywords: Enzyme modulation ; Nitrate reductase ; Protein kinase ; Protein phosphorylation ; Protein purification ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a three-step purification procedure, two protein fractions which catalyzed the ATP-dependent in-activation of nitrate reductase (NR) were obtained from spinach (Spinacia oleracea L.) leaf extracts. Purification involved ammonium-sulfate fractionation, anion-exchange chromatography and size-exclusion chromatography. The capacity of the fractions to inactivate NR by preincubation with ATP was examined by using as target either a crude NR-ammonium sulfate precipitate or partially purified NR (ppNR). The fractions were also examined for protein-kinase activity by measuring the phosphorylation of histone III S (or casein) with γ-[32P]ATP as substrate, and subsequent SDS-PAGE, autoradiography and liquid scintillation counting of cut-off histone bands. The two proteins had apparent molecular weights in the 67-kDa and 100-kDa region (termed P67 and P100, respectively). Neither P67 nor P100 alone was able to inactivate ppNR by preincubation with ATP. However, when P100 and P67 were added together to ppNR, ATP-dependent inactivation was observed, with a half-time of about 10 min. The P67, but not P100 had histone-kinase activity (casein was not phosphorylated). Using the partially purified system, various compounds were examined as possible effectors of NR inactivation. Sugar phosphates had little effect on the inactivation of NR. Addition of AMP at very high concentrations (5 mM), and removal of Mg2+ by excess EDTA also prevented the inactivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194451
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  • 5
    Electronic Resource
    Electronic Resource
    Partial purification of two proteins (100 kDa and 67 kDa) cooperating in the ATP-dependent inactivation of spinach leaf nitrate reductase (1994)
    Springer
    Planta 192 (1994), S. 183-188 
    Details
    ISSN: 1432-2048
    Keywords: Enzyme modulation ; Nitrate reductase ; Protein kinase ; Protein phosphorylation ; Protein purification ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a three-step purification procedure, two protein fractions which catalyzed the ATP-dependent in-activation of nitrate reductase (NR) were obtained from spinach (Spinacia oleracea L.) leaf extracts. Purification involved ammonium-sulfate fractionation, anion-exchange chromatography and size-exclusion chromatography. The capacity of the fractions to inactivate NR by preincubation with ATP was examined by using as target either a crude NR-ammonium sulfate precipitate or partially purified NR (ppNR). The fractions were also examined for protein-kinase activity by measuring the phosphorylation of histone III S (or casein) withγ-[32P]ATP as substrate, and subsequent SDS-PAGE, autoradiography and liquid scintillation counting of cut-off histone bands. The two proteins had apparent molecular weights in the 67-kDa and 100-kDa region (termed P67 and P100, respectively). Neither P67 nor P100 alone was able to inactivate ppNR by preincubation with ATP. However, when P100 and P67 were added together to ppNR, ATP-dependent inactivation was observed, with a half-time of about 10 min. The P67, but not P100 had histone-kinase activity (casein was not phosphorylated). Using the partially purified system, various compounds were examined as possible effectors of NR inactivation. Sugar phosphates had little effect on the inactivation of NR. Addition of AMP at very high concentrations (5 mM), and removal of Mg2+ by excess EDTA also prevented the inactivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089033
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  • 6
    Electronic Resource
    Electronic Resource
    Inactivation of nitrate reductase involves NR-protein phosphorylation and subsequent ‘binding’ of an inhibitor protein (1995)
    Springer
    Planta 195 (1995), S. 514-518 
    Details
    ISSN: 1432-2048
    Keywords: Inhibitor protein ; Nitrate reductase ; Protein phosphorylation ; Protein kinase ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The function of two proteins (P67 and P100) required for the MgATP-dependent inactivation of nitrate reductase (NR) from spinach leaves (Spinacia oleracea L.) was studied. When NR was incubated with γ-[32P]ATP and P67, NR-protein was phosphorylated, but without a change in NR activity. Protein P100 by itself was neither able to phosphorylate nor to inactivate NR, and when added together with P67 it did not change the extent of NR phosphorylation. However, when NR was first phosphorylated with MgATP and P67, subsequent addition of P100 after removal of unreacted ATP caused an immediate NR inactivation. In presence of both P67 and P100 the time-course of ATP-dependent NR phosphorylation paralleled the time course of inactivation. The extent of NR phosphorylation and of NR inactivation (in the presence of P67 plus P100) was similarly affected by metabolites or high salt concentrations. Magnesium (Mg2+) played a dual role in the inactivation process: the phosphorylation of NR by P67 was strictly Mg2+-dependent. Further, phospho-NR (+P100) was inactive only in the presence of Mg2+, but active in the presence of excess EDTA. Dephospho-NR appeared to be Mg2+-insensitive. The observations suggest that phosphorylation of NR by P67 is obligatory, but not sufficient for inactivation. In addition to protein phosphorylation, inactivation requires “binding” of an inhibitor protein (P100) to phospho-NR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195708
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  • 7
    Electronic Resource
    Electronic Resource
    Cyansäureester, XIX. Über die Elektronenstrukturen von Arylcyanaten, Arylthio- und Arylselenocyanaten (1969)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 102 (1969), S. 2508-2519 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Von Phenylcyanat und einigen p-substituierten Arylcyanaten wurden die Dipolmomente bestimmt und nach dem LCAO-MO-Verfahren die Doppelbindungsgrade, π-Elektronendichten und freien Valenzen berechnet. Die Substituentenkonstanten der OCN-Gruppe wurden aus der chemischen Verschiebung der 19F-Resonanzsignale von p- und m-Fluor-phenylcyanat gegenüber Fluorbenzol und aus den integralen Intensitäten der νC=C-Aromatenbanden des Phenylcyanats zu σI = +0.75 ± 0.04 und σR0 = -0.27 ± 0.07 ermittelt. Die aus den Ergebnissen abgeleiteten Schlußfolgerungen lassen Angaben über das elektronische Verhalten von Atomen der 6. Hauptgruppe zu, die von einem Aromaten und einer Nitrilgruppe flankiert sind.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19691020804
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  • 8
    Electronic Resource
    Electronic Resource
    Tetraphenylarsonium-tetrachloromonoazidotitanat (IV); Darstellung, IR-Spektrum und Kristallstruktur von (AsPh4)2 [TiCl4N3]2 (1980)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 468 (1980), S. 172-178 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tetraphenylarsonium Tetrachloromonoazidotitanate(IV); Preparation, I.R. Spectrum, and Crystal Structure of (AsPh4)2[TiCl4N3]2The title compound was obtained from TiCl4 and AsPh4N3 in H2CCl2 solution in form of yellow crystals. Its crystal structure was determined with X-ray diffraction data and was refined to a residual index of R = 4.2%. (AsPh4)2[TiCl4N3]2 crystallizes in the space group P1 with one formula unit per unit cell. The [TiCl4N3]2- ion is situated on a crystallographic inversion center and beyond that fulfills the point symmetry C2h in good approximation. The two Ti atoms are linked via the α-N atoms of the azido groups forming a planar (TiN)2 ring. The azido groups are inclined by 20° towards the ring plane. The i.r. Spectrum was recorded and assigned.
    Notes: Die Titelverbindung entsteht aus Titantetrachlorid und Tetraphenylarsoniumazid in Dichlormethanlösung in Form gelber, feuchtigkeitsempfindlicher Kristalle. Die Kristallstruktur wurde mit Röntgenbeugungsdaten aufgeklärt und bis zu einem Übereinstimmungsindex von R = 4,2% verfeinert. (AsPh4)2[TiCl4N3]2 Kristallisiert triklin (Raumgruppe P1) mit einer Formeleinheit pro Elementarzelle. Das [TiCl4N3]2--Ion befindet sich in einem kristallographischen Inversionszentrum und erfüllt darüber hinaus in guter Näherung die Punktsymmetrie C2h. Die beiden Ti-Atome sind über die α-N-Atome der Azidogruppen verknüpft unter Ausbildung eines planaren (TiN)2-Rings. Die Azidogruppen sind 20° gegen die Ringebene geneigt. Das IR-Spektrum wurde registriert und zugeordnet.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19804680121
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  • 9
    Electronic Resource
    Electronic Resource
    Azidokomplexe des Zirkoniums: ZrCl3N3, [ZrCl4N3]22⊝, [ZrCl4(N3)2]2⊝; die Kristallstruktur von (PPh4)2[ZrCl4N3]2 (1981)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 482 (1981), S. 113-120 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azido Complexes of Zirconium: ZrCl3N3, [ZrCl4N3]22⊝, [ZrCl4(N3)2]2⊝; Crystal Structure of (PPh4)2 [ZrCl4N3]2Highly explosive ZrCl3N3 is formed by the reaction of ZrCl4 with iodine azide in dichloromethane suspension. According to the i.r. spectra, the compound is polymeric by azide and chlorine bridges. Zirconium tetrachloride reacts with one and two moles of tetraphenylphosphonium azide respectively, forming the thermally and mechanically stable complexes (PPh4)2[ZrCl4N3]2 and (PPh4)2[ZrCl4(N3)2]. The crystal structure of (PPh4)2[ZrCl4N3]2 was determined by X-ray methods (1942 reflexions, R = 6.5%). The complex crystallizes in the monoclinic space group P21/n with two formula units per unit cell. The structure consists of tetraphenylphosphonium cations and dimeric anions [ZrCl4N3]22⊝, in which the Zr atoms are linked by the α-N atoms of the azide groups, forming a centrosymmetric Zr2N2 ring with symmetry D2h. According to the i.r. spectra, the azide groups in the complex (PPh4)2[ZrCl4(N3)2] are covalently bonded at the Zr atom in trans positions.
    Notes: Hochexplosives ZrCl3N3 entsteht aus Zirkoniumtetrachlorid und Iodazid in Dichlormethan-Suspension. Nach dem IR-Spektrum liegt ein über Azido- und Chlorobrücken verknüpftes Polymer vor. Zirkoniumtetrachlorid bildet mit einem bzw. zwei Mol Tetraphenylphosphoniumazid die thermisch und mechanisch stabilen Komplexe (PPh4)2[ZrCl4N3]2 und (PPh4)2[ZrCl4(N3)2] Die Kristallstruktur von (PPh4)2[ZrCl4N3]2 wurde mit Röntgenbeugungsdaten ermittelt (1942 Reflexe, R = 6,5%). Die Verbindung kristallisiert monoklin in der Raumgruppe P21/n mit zwei Formeleinheiten pro Elementarzelle. Es liegen Tetraphenylphosphoniumkationen und dimere Anionen [ZrCl4N3]22⊝ vor, in denen die Zirkoniumatome durch die α-N-Atome der Azidgruppen zu einem zentrosymmetrischen Zr2N2-Vierring der Symmetrie D2h verknüpft sind. In dem Komplex (PPh4)2-[ZrCl4(N3)2] sind die Azidogruppen nach dem IR-Spektrum kovalent an das Zr-Atom gebunden und in trans-Position zueinander angeordnet.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19814821113
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