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51.
Lafaye A Junot C Ramounet-Le Gall B Fritsch P Tabet JC Ezan E 《Rapid communications in mass spectrometry : RCM》2003,17(22):2541-2549
This work reports the use of reverse-phase liquid chromatography coupled to electrospray ion trap (QIT) mass spectrometry for the analysis of the metabolome in rat urine. An injection of 20 microL of urine into the chromatographic system is followed by a slow gradient elution and mass spectrometric detection in the scanning mode from m/z 100-1000 in both positive and negative modes. Over a time scale of 90 min, 30 and 20 resolved peaks were observed in the positive and the negative modes, respectively, corresponding to the presence of a few hundred m/z ratios. By using a QIT analyzer, data-dependent tandem mass spectrometry of selected m/z ratios identified several compounds in rat urine and characterized various chemical families, including carboxylic acids, amines, sulfated compounds, glucuronides and glycosides, by the observation of characteristic fragment ions or neutral losses. The method has been applied to the investigation of the chronic toxicity of heavy metals in rat urine. A few tens of m/z ratios, differing in intensity more than threefold from control values, were observed in both positive and negative modes. The time variations for some selected ions suggest that LC/ESI-MS could allow selective characterization of biomarkers in response to specific toxic compounds. 相似文献
52.
Anne Astier Jean-Claude Daran Yves Jeannin Catherine Rigault 《Journal of organometallic chemistry》1983,241(1):53-68
Syntheses and single-crystal X-ray diffraction studies have been completed on two cycloruthenapentadienyl (CO)6Ru2L2 derivatives, with L = CH2OHC = CCH2OH and C2H5C=CCH2CH2OH respectively. Crystal data are as follows: for [(CO)3RuC4(CH2OH)4]Ru(CO)3·H2O, P21/c, a 13.72(1), b 9.501(4), c 14.86(1) Å, β 101.10(6)°, Rw = 0.052 for 1911 reflections; for [(CO)3RuC4(CH2CH2OH)2(C2H5)2]Ru(CO)3, P21/c, a 9.191(3), b 16.732(4), c 14.903(3) Å, β 113.61(4)°, Rw = 0.042 for 2865 reflections. Both compounds are built up from binuclear units, each unit being regarded as a Ru(CO)3 fragment π-bonded to a cycloruthenapentadienyl ring. The molecular parameters are compared with those of known cyclometallapentadienyl complexes of transition metals. The presence of a semi-bridging CO group is discussed. 相似文献
53.
54.
Monique Nanot Francine Queyroux Jean-Claude Gilles 《Journal of solid state chemistry》1979,28(2):137-147
The homologous phases corresponding to the formula AnBnO3n+2 observed in the systems: La2Ti2O7CaTiO3, Nd2Ti2O7CaTiO3 and Ca2Nb2O7CaTiO3, have a structure derived from the structure of perovskite by periodic crystallographic shears, which delimitate n octahedra thick sheets. In the [0 1 0]1 direction, the sheets are following each other with two types of arrangement.Crystals of terms n = 4,5, 5 and 6 were investigated by X-ray diffraction. According to the type of arrangement of the sheets, the phases studied have either an orthorhombic symmetry or a monoclinic symmetry, this last one giving rise to merohedral twins. 相似文献
55.
Jean-Claude Leclerc 《International journal of quantum chemistry》1976,10(5):781-789
Introduction of noninteger powers of r (or the elliptical coordinate ξ) in the definition of the 1s AO is shown to give better approximate wave-functions for the ground states of H2 and He than other functions of comparable complexity. This trend is examined for various definitions of hybrid Slater–Gaussian orbitals using a limited CI . The best optimized single-term expansion energy is only 0.000160 a.u. above the “SCF limit” for H2 at R = 1.4 a.u. and 0.000382 a.u. for He at R = 1.3 a.u. 相似文献
56.
The palladium-catalyzed benzylic-like nucleophilic substitution of acetates derived from benzofuran, benzothiophene and indole was investigated. The asymmetric substitution on racemic 1-(2-benzofuryl)ethyl acetate gave disappointing results, but the substitution product was obtained in 98% ee from (S)-1-(2-benzofuryl)ethyl acetate with overall retention of configuration. 相似文献
57.
Jean-Claude Berthet Jean-Francois Le Mar chal Michel Ephritikhine 《Journal of organometallic chemistry》1994,480(1-2):155-161
The monocyclooctatetraene uranium complex [U(COT)(I)2(THF)2] (COT=η-C8H8; THF=tetrahydrofuran), isolated from the reaction of bis(cyclooctatetraene)uranium with iodine, is a precursor for the synthesis of the alkyl derivatives [U(COT)(CH2Ph)2i (HMPA) 2], [U(COT)(CH2SiMe3)2(HMPA)] (HMPA=hexamethyl phosphorous triamide) and [U(COT)CH2SiMe3)3] [Li(THF)3] and of the mixed-ring compounds [U(COT)(η-C5R5)(I)] (R=H or Me). The last were used to prepare the amide and alkyl complexes [U(COT)(η-C5H5)(N{SiMe3}2)] and [U(COT)(η-C5Me5)(CH2SiMe3)]. 相似文献
58.
Classical inhibitors of human cytochrome P450 3A4 activity, such as ketoconazol and quercetin, are tested to prove the efficiency of a new metabolisation model using living entire cells. Grapefruit juice is a well-known potent inhibitor of cytochrome P450 3A4 activity. With regard to the clinical relevance of grapefruit juice-drug interactions, an investigation of other common juices is undertaken with this in vitro model. The CYP3A4 activity is measured by the formation of the 6beta-hydroxytestosterone, which is quantified by an isocratic high performance liquid chromatography. It is demonstrated for the first time that lemon juice significantly inhibits by 60+/-3% the CYP3A4-mediated oxidation. Grapefruit juice inhibits this activity by 82+/-4%. The mechanism of lemon juice inhibition is competitive, whereas it is mixed for grapefruit juice. These results suggest that our in vitro model combined with our analytical method is applicable for the investigation of the inhibition of CYP3A4 not only by chemical inhibitors but also by natural food products. 相似文献
59.
Budimir N Fournier F Bailly T Burgada R Tabet JC 《Rapid communications in mass spectrometry : RCM》2005,19(13):1822-1828
The tripodal ligand N,N,N-tris[(1,hydroxy-2-pyridinon-6-yl)amide]propylamine was synthesized. It is composed of an anchor (nitrogen atom), a functional group (hydroxamate), and also a spacer of variable length defined by the number of methylene groups linking the anchor and the functional group. The characterization of this ligand in the presence of several divalent metal cations (Fe(II), Mn(II), Co(II) and Cu(II)), performed by electrospray ionization mass spectrometry (ESI-MS and ESI-MS/MS), allowed elucidation of oxidation states and also of different fragmentation patterns. The importance of the spacer length was studied in the case of the iron binary complex by comparing this ligand with another with a shorter spacer. In this way the stabilizing conditions, in which hydrogen bonds are implicated, were clarified. 相似文献
60.
The sensitivity of saturated aliphatic ketone stretching frequencies, vCO to structure and solvent effects is expressed by a four-term equationvco = 1740 + I(XXX) -0.24 G + 2.10?3G ·I(XXX)The four terms represent: the frequency of the base element (acetone) calculated in the absence of intermolecular interactions; the contribution of intramolecular environment E given by structure parameter I(itXXX) previously established in gas phase; that of the intermolecular environment related to the Allerhand and Schleyer G parameter; that of solvent-solute interactions. This equation covers an experimental range of 78 cm?1 for 192 measurements in four highly diverse solvents (C6H14, CC14, CH3CN, CHBr3) with a standard deviation of 1.6 cm?1; it expresses an overall statistical behavior, but masks individual behaviors. The latter are determined by comparing two characteristic parameters of ketones, a topological parameter I(XXX), and p expressing solvent sensitivity [slope of straight lines ν = f(G)]; they are Interpreted in terms of geometrical effect, variation of valency angles and of conformations. 相似文献