中性盐对谷氨酸脱羧酶活性的影响机制

通过不同阳离子和不同阴离子对唾液链球菌嗜热亚种(Streptococcus salivariussub sp.thermophilus)谷氨酸脱羧酶活性的影响以及NaNO3对不同蛋白质浓度的谷氨酸脱羧酶活性的影响进行考察,结果表明:中性盐对谷氨酸脱羧酶活性的影响不是由于增加蛋白质亚基间的疏水作用引起的,而可能是由中性盐对谷氨酸脱羧酶活性的弱抑制作用与中性盐增加了谷氨酸脱羧酶的胶体体系稳定性共同作用所致,同时还可能与中性盐降低了反应体系CO2的溶解度有关.     

Mittlere ringe-XIII Die intramolekulare acylierung der ω-(1-naphthyl)-fettsäuren

The intramolecular Friedel-Crafts cyclisation of ω-arylalkanoic acids, which is in the benzene series a valuable synthetic route to bicyclic ketones with medium-sized and large rings, has been investigated with ω-(1-naphthyl)alkanoyl chlorides. The lower members, including naphthyl-caproic acid, close the ring at position 2 to form IV. The higher homologous acids show a preference for annellation at 7, making available a new type of heteronuclear naphthalene cyclic ketones (VII). During cyclisation of ω-(1-naphthyl) decanoic acid, the 1,4 ring closure competes with the 1,7 type.

Steric hindrance of resonance as a consequence of “medium ring torsion” was studied in different classes of naphthocyclenones.     

The stereochemistry of quaternary N-methyl sparteinium cations, their derivatives, stereoisomers and analogues : Part II. Molecular and crystal structure, and IR spectra of methiodide and methperchlorate of 2-oxosparteine

The crystal and molecular structures of two quarternary salts of 2-oxosparteine (II), the methiodide (IICH⁺₃ • I⁻) and the methperchlorate (IICH⁺₃ • ClO⁻₄) have been determined on the basis of X-ray and IR data. The studies were performed by analogy to previously investigated quaternary salts of sparteine (I), the methiodide (ICH⁺₃ • I⁻) and the methperchlorate (ICH⁺₃ • ClO⁻₄). As expected, the configurations and conformations of cationic parts within the two pairs of quaternary salts are identical, except for the structure of their A/B fragments, which in ICH⁺₃ cations have the character of tertiary amines, but in IICH⁺₃ that of lactams.

On the basis of accumulated X-ray and IR data the similarities and differences in the modes of interaction of perchlorate and iodide anions with quaternary cations, and especially with their N⁺---CH₃ groups are discussed. In this discussion are also included the methiodide and methperchlorate of -isosparteine: IIICH⁺₃ • X⁻ (X⁻ = I⁻ or ClO⁻₄) where N⁺---CH₃ groups are cisoidally oriented to the basic nitrogen atoms. The most interesting observations are as follows: (i) When N⁺---CH₃ groups are easily accessible for direct quasi hydrogen bonding interactions with counter anions and when other positive charged groups, for instance lactam groups, are absent in quaternary cations, perchlorate anions interact more strongly than the iodide anions and in consequence introduce conformational changes into the ring with N⁺---CH₃ group as well as into further rings. (ii) Perchlorate and iodide anions interact with N⁺---CH₃ groups similarly and very weakly if at all, when the N⁺---CH₃ groups are for steric reasons inaccessible to counter anions or when in quaternary cations there are additional groups which attract the counter anions electrostatically. The last mechanism operates in both quaternary salts of 2-oxosparteine and this is the reason why their monocrystals are isosteric and IR spectra almost identical. (iii) The sterically hindered N⁺---CD₃ groups in both IIICD⁺₃ • X⁻ salts give rise in their IR spectra to two doubles of sharp, well resolved bands which indicate the presence of two different rotamers stabilized by two modes of weak intramolecular hydrogen bonds with basic N atoms. (iv) In IIICH⁺₃ • X⁻ and IIICD⁺₃ • X⁻ salts the perchlorate and iodide anions do not interact at all with the rotating and vibrating N⁺---CH₃ (N⁺---CD₃) group but the structures of these salts are not isosteric since the perchlorate anions interact more strongly than iodide anions with the A/B fragment of the IIICH⁺₃ cations. This is visible from the shapes and intensities of the so-called “trans” band in the IR spectra of both salts.     

Raman scattering from Pt(CN)42− adsorbed on Pt colloids

Raman scattering from Pt(CN)₄^2? adsorbed on Pt colloids (average diameter of 16 A) is compared with the Raman signal from the same amount of Pt(CN)₄^2? in solution. The wavelength dependence of the adsorbate Raman intensity is measured from 308 to 647 nm and compared with a Lorenz/Mie calculation of the enhancement factor for the electromagnetic field intensity on the surface of a Pt sphere as a function of sphere radius and incident wavelength.     

Equilibrium studies of Mn(II), Mg(II), Ca(II), Sr(II) and Ba(II) withp-fluoro-,p-chloro-,p-bromo-,p-methyl-benzoylacetones and 1-(4-fluorophenyl)-1,3-pentanedione

The rawpH-data, obtained from the potentiometric titrations of the titled ligands with NaOH in 75% (v/v) dioxane-water mixture performed at 20, 30 and 40°C at constant ionic strength (=0.1M-NaClO₄), have been adequately corrected for dilution, and solvent effects in order to evaluate thermodynamic dissociation constants. Variance of the latter as a function of temperature has also been accounted for. The differing magnitudes of thermodynamic dissociation constants of the titled ligands have been explained on the basis of the non coplanar orientation of the phenyl ring in the ligands and a comparison has been made with those of unsubstituted benzoylacetone, dibenzoylmethane and acetylacetone.Following similar technique, thermodynamic stepwise and overall formation constants of the titled metal-ligand systems have been obtained and the results correlated with ligand basicity inverse metal crystal radii and second potentials of metals. Decrease in the free enthalpy (–G) of complexation reaction has also been evaluated.

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Untersuchung der Gleichgewichte von Mn(II), Mg(II), Ca(II), Sr(II) und Ba(II) mit p-Fluor-, p.-Chlor-, p-Brom-, p-Methyl-benzoylaceton und 1-(4-Fluorphenyl)-1,3-pentanedion

Zusammenfassung Aus der potenitometrischen Titration der Titelverbindungen mit NaOH in 75 (v/v) Dioxan—Wasser bei, 20, 30 und 40°C bei konstanter Ionenstärke (=0,1M-NaClO₄) wurden die thermodynamischen Dissoziationskonstanten ermittelt. Verdünnungs-, Lösungsmittel-und Temperatureffekte wurden berücksichtigt. Die unterschiedlichen Dissoziationskonstanten werden mit der Nichtplanarität des Phenylrings in den Liganden erklärt. Außerdem wurden die Komplexbildungskonstanten bestimmt; sie sind in die Diskussion miteinbezogen.

     

Synthesis and transformations of metallacycles. 23. Cp2TiCl2-Catalyzed cyclometallation of fullerene C60 with EtAlCl2

1-Ethyl-2,3-fullerenoaluminacyclopropanes (EtAl)_n(²-C₆₀) were synthesized by the reaction of fullerene C₆₀ with an excess of EtAlCl₂ in the presence of Mg and using Cp₂TiCl₂ as the catalyst in a THF--toluene solution at 20 °C. Deuterolysis of fullerenoaluminacyclopropanes afforded a mixture of deuteriofullerenes C₆₀D_m, where m = 6--12.     

Supramolecular structures of macromolecules containing bipyridine–copper(I) complexes as revealed from transmission electron microscopy studies

Transmission electron microscopy (TEM) studies on bipyridine (bpy) containing block copolymer systems showed the formation of nanoscopic polymer–ion complexes through complexation with copper(I) ions which segregated to highly ordered columnar domains of mesoscopic dimensions. The domains, i.e. stacks of [(bpy)₂Cu(I)] complex moieties could be visualized by complementary TEM techniques. First, electron energy loss spectra (EELS) showed the absorption edges of copper and nitrogen, which are specific for the bipyridine copper complexes. The element spectroscopic imaging (ESI) technique allowed the imaging of the net copper and net nitrogen distribution, and the coinciding pictures exhibited a microphase separated system in the case of a 3-block copolymer with complexed end segments. High resolution elastic bright field images showed interference lines with a line to line distance of about 8 A which could be related to the Cu–Cu distance in staggered Cu(I)–bipyridine complexes. Received: 6 August 1997 Accepted: 28 April 1998     

Darstellung und Kristallstruktur von HgPb2O(OH)Br3

Inhaltsübersicht. Die erstmals dargestellte Verbindung HgPb₂O(OH)Br₃ kristallisiert orthorhombisch in der Raumgruppe Aba2 (Nr. 41) mit den Gitterkonstanten a = 14,652(3) Å, b = 14,6491(8) Å, c = 7,782(2) Å und Z = 8. Die Bestimmung der Kristallstruktur mit Einkristallmethoden zeigte “isolierte”, verzerrt würfelförmige Baugruppen der Zusammensetzung [Hg₂Pb₄O₂(OH)₂]. Diese Einheiten werden von Bromidionen umhüllt. HgPb₂O(OH)Br₃ stellt damit hinsichtlich des strukturellen Aufbaus ein Bindeglied zwischen den Verbindungen [Pb₄(OH)₄](ClO₄)₄ · 2H₂O [1] und Pb₉O₄Br₁₀ [2] dar. Preparation and Crystal Structure of HgPb₂O(OH)Br₃ The new compound, HgPb₂O(OH)Br₃ was prepared and investigated by X-ray crystal structure analysis. Crystals of orthorhombic symmetry show space group Aba2 (No. 41) with lattice parameters a = 14.652(3) Å, b = 14.6491(8) Å, c = 7.782(2) Å, and Z = 8. Remarcable structural units with heterocubane skeleton were found. The [Hg₂Pb₄O₂(OH)₂] group forms a new member of the structural class between [Pb₄(OH)₄] and [Pb₈O₄] units with the relating compounds [Pb₄(OH)₄)](ClO₄)₄ · 2 H₂O [1] und Pb₉O₄Br₁₀ [2].     

Copolymer of Di (methacryloyloxymethyl) naphthalene and divinylbenzene as a column packing for high-performance liquid chromatography

Summary A new porous polyaromatic ester packing was synthetized for high performance liquid chromatography. The relationship between retention and chain length of the members of homologous series of alkylbenzenes, N-alkylanilines, alkylarylethers, alkylbenzoates and alkylarylketones on this new stationary phase using different eluents was investigated. Using the alkylarylketone scale the retention indices of the homologues and test compounds were calculated. The results were compared with those obtained for poly (styrene-divinylbenzene) polymers. For both types of packing the first members of each homologous series gave non-linear behaviour. The methylene group index increments are different for the studied homologous series; thus there is no simple additivity of the retention indices. The efficiency of the porous polymeric columns is a function of the capacity factor of the solute and the organic component of the eluent.     

Molecular aggregation in the ternary system deca glycerol dioleate/heptane/water

The phase diagram for the ternary system deca glycerol dioleate(DGD)/heptane/water was established at 25 °C. In this phase diagram it was seen that the reverse micellar solution phase extends in its area until the water content reaches 35–45 wt%, at which a liquid crystalline phase begins to appear. On the basis of the experimental results of specific conductivity, viscosity, etc. for the samples containing a definite amount of DGD (0,1 M), and varying relative amounts of heptane and water, the mechanism of the transition of reverse micellar structures to liquid crystalline phase is discussed.