Comparative energetics of glucose and xylose metabolism in ethanologenic recombinantEscherichia coli B

This study compared the anaerobic catabolism of glucose and xylose by a patented, recombinant ethanologenicEscherichia coli B 11303:pLOI297 in terms of overall yields of cell mass (growth), energy (ATP), and end product (ethanol). Batch cultivations were conducted with pH-controlled stirred-tank bioreactors using both a nutritionally rich, complex medium (Luria broth) and a defined salts minimal medium and growth-limiting concentrations of glucose or xylose. The value of Y_ATP was determined to be 9.28 and 8.19 g dry wt cells/mol ATP in complex and minimal media, respectively. Assuming that the nongrowth-associated energy demand is similar for glucose and xylose, the mass-based growth yield (Y _x/s , g dry wt cells/g sugar) should be proportional to the net energy yield from sugar metabolism. The value ofY _x/s was reduced, on average, by about 50% (from 0.096 g/g glu to 0.051 g/g xyl) when xylose replaced glucose as the growth-limiting carbon and energy source. It was concluded that this observation is consistent with the theoretical difference in net energy (ATP) yield associated with anaerobic catabolism of glucose and xylose when differences in the mechanisms of energy-coupled transport of each sugar are taken into account. In a defined salts medium, the net ATP yield was determined to be 2.0 and 0.92 for glucose and xylose, respectively.     

Compounds of nickel(II) with 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rmL: The structures of [Ni(rmL)](ClO4)2 · 0.5H2O and cis-[Ni(rmL)(acac)]ClO4

The imine functions of [Ni(mL¹)](ClO₄)₂ (mL¹ = meso-7RS,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) are reduced by using NaBH₄ in acetonitrile/methanol to form the meso–meso and rac–meso isomeric cyclic tetramine complex cations [Ni(mmL²)]²⁺ and [Ni(rmL²)]²⁺ (mml² = 5RS,7RS,12SR,14SR- and rmL² = 5SR,7RS,12SR,14SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) in ca. 8:1 proportions. [Ni(rmL²)]²⁺ is also prepared from rmL², formed in <1% yield by the reduction of mL¹ by NaBH₄ in ethanol. Square planar singlet ground state (S = 1) salts [Ni(rmL²)](ClO₄)₂ and [Ni(rmL²)][ZnCl₄] and triplet ground state (S = 3) trans-di-ligand octahedral compounds trans-[Ni(rmL²)X₂] ,μ-Y-trans-[Ni(rmL²)Y] and folded macrocycle compounds cis-[Ni(rmL²)(acac)]CIO₄ (acac⁻ = pentane-2,4-dionato), cis-[{Ni(rmL²)}₂(C₂O₄)](ClO₄)₂, cis-[Ni(rmL²)(H₂O)₂](ClO₄)₂ and cis-[Ni(rmL²)X₂], X⁻ = Cl⁻, Br⁻, are described. The S = 1 salt 1SR,4SR,5SR,7RS,8RS,11RS,12SR,14SR-[Ni(rmL²)](ClO₄)₂ · 0.5H₂O has a disordered structure with Ni(II) in square planar coordination by the nitrogen atoms of the macrocycle, in N-configuration III, with Ni–N_mean = 1.96(2) Å. The six-membered chelate rings both have chair conformations, with the phenyl substituents equatorially oriented and with the methyl substituents disordered over axial and equatorial orientations. The S = 3 compound cis-1SR,4SR,5SR,7RS,8SR,11SR,12SR,14SR-[Ni(rmL²)(acac)]ClO₄ has N-configuration V. The macrocycle is folded along N¹–Ni–N⁸, adjacent to the phenyl substituents {N1–Ni–N8 = 176.45(6), N4–Ni–N11 = 98.16(6)°}, with mean Ni–N = 2.09(2) Å and mean Ni–O = 2.121(5) Å. Both six-membered chelate rings have chair conformations with the methyl substituents equatorially oriented, while one has the phenyl substituent equatorially and the other has it axially oriented. The structures of the isomeric [M(rmL²)(acac)]ClO₄, [M(rrL²)(acac)]CIO₄ and [M(mmL²)(acac)]ClO₄ compounds are compared.     

Zur Bildung von Fullerenen und endohedralen Metallofullerenen: Darstellung im Hochfrequenzofen

Formation of Fullerenes and Endohedral Metallofullerenes: Preparation in a Radiofrequency Furnace A thermodynamic analysis of the reaction of formation is presented for C₆₀. The alternative route for the preparation of fullerenes by evaporating carbon in a RF-furnace is described. This process is characterized by its broad variability and by comparatively mild conditions which, in addition, may be measured and controlled rather precisely. Thus, it offers favorite facilities for the production of soots with high contents of fullerenes and endohedral fullerenes. So far, LaC₈₂ could be extracted using toluene.     

Synthesis and luminescent properties of Eu-complexes with 2-acyl-1,3-indandionates (ACIND) and TPPO ligands: The first X-ray structure of Eu–ACIND complex

Europium complexes presenting general formulas [Eu(ACIND)₃(H₂O)₂] and [Eu(ACIND)₃(TPPO)₂] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)₃(H₂O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P2₁/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C_2ν. Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process.     

The electronic structures of urazole,pyrrole, and their ions. The σ-π separability problem

Ab initio all-electron LCGTO-SCF-MO calculations have been made on the 5-membered ring nitrogen heterocycles urazole (C₂H₃N₃O₂), pyrrole (C₄H₅N), and their ion radicals. Wavefunctions were obtained, population analyses made, and electron density contour maps drawn. The results show that for urazole considerable polarity develops in the bonds as a result of a large shift of charge towards the nitrogen atoms at the expense of the carbon and hydrogen atom -electrons with only little effect on the oxygen atom charges. In addition, it is concluded that the -electron approximation should be used with great caution for this type of molecule since the - separability conditions are not well satisfied.

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Zusammenfassung Für die Fünfring-Stickstoffheterocylen Urazol (C₂H₃N₃O₂), Pyrrol (C₄H₅N) und ihre Ionenradikale wurden ab initio Rechnungen nach der LCGTO-SCF-MO-Methode durchgeführt, wobei alle Elektronen berücksichtigt wurden. Die Besetzungszahlen wurden ermittelt und die Elektronendichten graphisch dargestellt. Die Rechnungen zeigen, daß für Urazol eine beträchtliche Polarität in den -Bindungen vorhanden ist. Der Grund dafür liegt in der starken Verschiebung der -Ladung in Richtung des Stickstoffatoms auf Kosten der -Elektronen des Kohlenstoffs und Wasserstoffs. Die -Ladungen am Sauerstoff werden kaum beeinflußt. Von einer -Elektronenapproximation für diese Art von Molekülen wird abgeraten, da die --Separationsbedingungen nur ungenügend erfüllt werden.

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Résumé Calculs ab-initio LCGTO-SCF-MO pour tous les électrons des hétérocycles pentagonaux: urazole (C₂H₃N₃O₂), pyrrole (C₄H₅N) et de leurs ions-radicaux. Après obtention des fonctions d'onde, l'analyse de population est affectuée et les cartes de densité électronique sont dréssées. Les résultats indiquent que l'urazole présente une forte polarité dans les liaisons sigma résultant d'un transfert de charge sigma vers les atomes d'azote aux dépens des atomes de carbone et d'hydrogène et en affectant peu les atomes d'oxygène. De plus, la séparabilité sigma pi n'est pas bien satisfaite dans ce type de molécule.

     

Determination of total taurine in pet foods by liquid chromatography of the dansyl derivative: collaborative study

A liquid chromatographic (LC) method for the determination of total taurine in pet foods was evaluated in a collaborative study. Ten laboratories assayed 6 blind duplicate pairs of wet and dry pet foods. The taurine in the 6 sample pairs ranged from low (170 mg/kg) to high (2250 mg/kg) concentrations as is. Collaborators also assayed a sample of known taurine concentration for familiarization purposes. Samples were hydrolyzed to release bound taurine, which was subsequently converted to the dansyl derivative and quantitated by gradient-elution LC with fluorescence detection. Repeatability relative standard deviations, RSDr, ranged from 3.2 to 10.0%; reproducibility relative standard deviations, RSDR, ranged from 6.1 to 16.1%. The method has been adopted Official First Action status by AOAC INTERNATIONAL.     

Low‐dimensional compounds containing cyano groups. I. catena‐Poly[[[dicyanoargentato(I)‐κN]bis(4‐methylpyridine‐κN)copper(II)]‐μ‐dicyanoargentato(I)‐κ2N:N′]

The structure of the title compound, [Cu(C₆H₇N)₂{Ag(CN)₂}₂]_n, is made up of neutral zigzag chains of [–NC–Ag–CN–Cu(4‐Mepy)₂{Ag(CN)₂}–NC–Ag–CN–] (4‐Mepy is 4‐methyl­pyridine). Neighbouring chains are linked by weak argentophilic interactions, with Ag?Ag distances of 3.2322 (12) Å. The Cu atom, which lies on a twofold rotation axis, is pentacoordinated by one monodentate Ag(CN)₂^? anion [Cu—N 1.985 (3) Å], the atoms of which lie on the same rotation axis, and by bridging di­cyano­argentate anions [2 × Cu—N 2.0827 (19) Å], with Ag atoms on inversion centres. The coordination polyhedron is completed by two 4‐Mepy mol­ecules [2 × Cu—N 2.038 (2) Å], which occupy the axial positions of a distorted trigonal bipyramid.     

Temperature‐dependent conformational analysis of cyclononane: An ab initio study

Quantum chemical methods were used for the theoretical determination of the conformational population for the relevant conformers of cyclononane, i.e., TBC, TCB, TCC, and M4 (or C1), which have been previously investigated experimentally through detailed examination of the nuclear magnetic resonance (NMR) spectrum. Our best Gibbs free energy result, evaluated with MP4(SDTQ)/6‐31G(d,p)//MP2/6‐31G(d,p) energy differences and MP2/6‐31G(d,p) thermal corrections, lead to a temperature‐dependent population in excellent agreement with the experimental results based on the analysis of the low temperature ¹³C NMR spectrum. The nice agreement with experiment is achieved using MP2 harmonic frequencies for the evaluation of vibration partition functions within the standard statistic thermodynamics formalism. Theoretical temperature‐dependent infrared (IR) and ¹³C NMR spectra were simulated and compared with experimental data, which confirmed the ab initio conformational population reported here. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Trialkylhydridoalanate RxR′3-xAlH⊖ [R = CMe3; R′ = CH(SiMe3)2]

Trialkylhydridoalanates R_xR′_3?xAlH^? [R = CMe₃; R′ = CH(SiMe₃)₂] The very strong base tert-butyl lithium reacts in the presence of chelating tetramethylethylendiamine with the aluminium organyls Al[CH(SiMe₃)₂]₂CMe₃ 1 and Al[CH(SiMe₃)₂](CMe₃)₂ 2 not under proton abstraction from the C? H acidic elementorganic substituent, but under β-elimination and addition of the thereby formed LiH to the coordinatively unsaturated aluminium atom. Two alanates — [Hal{CH(SiMe₃)₂}₂CMe₃]^? 3 and [HAl{CH(SiMe₃)₂}(CMe₃)₂]^? 4 each with Li(TMEDA)₂^⊕ as counterion — were isolated; they exhibit separate anions and cations in solid state as shown by a crystal structure determination on 3 . In absence of the chelating amine tert-butyl lithium decomposes under the catalytic effect of the aluminium compound to LiH, which does not add to aluminium and precipitates in a reactive form.     

Synthesis and circular dichroism studies of steroidal schiff bases of biogenic amines

A number of imines (Schiff bases) have been prepared from ketosteroids (estrone, estrone-3-methyl ether, androsterone, epiandrosterone, 5α-cholestan-3-one, 6-ketocholestanol and testosterone) and primary amines (phenethylamine, tyramine and hexanamine). The CD spectra of these compounds have been measured in methanol. Except for the testosterone imines, the azomethine n-π^* band (~ 235 nm) exhibited the same sign (but not as high an ellipticity) as the parent ketone's n - π^* band (~295 nm). The imines of the estrogens (estrone and estrone 3-methyl ether) gave CD spectra characterized by a negative ¹L_b Cotton effect ([θ] ? -1000) near 280 nm and a band near 230 nm ([θ] ? +19,000) which is considered the sum of a positive azomethine n - π^* Cotton effect and positive aromatic ¹L_a Cotton effect(s). The ¹L_a band originating in the amine moiety was prominent in the CD of 5α-cholestan-3-one and 6-ketocholestanol phenethylamine imines. When aromatic Cotton effects originating in the amine moiety were detected, they were of the same sign as the n - π^* Cotton effect.