Simultaneous analysis of 13C‐glutathione as its dimeric form GSSG and its precursor [1‐13C]glycine using liquid chromatography/isotope ratio mass spectrometry

Determination of glutathione kinetics using stable isotopes requires accurate measurement of the tracers and tracees. Previously, the precursor and synthesized product were measured with two separate techniques, liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) and gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). In order to reduce sample volume and minimize analytical effort we developed a method to simultaneously determine ¹³C‐glutathione as its dimeric form (GSSG) and its precursor [1‐¹³C]glycine in a small volume of erythrocytes in one single analysis. After having transformed ¹³C‐glutathione into its dimeric form GSSG, we determined both the intra‐erythrocytic concentrations and the ¹³C‐isotopic enrichment of GSSG and glycine in 150 µL of whole blood using liquid chromatography coupled to LC/IRMS. The results show that the concentration (range of µmol/mL) was reliably measured using cycloleucine as internal standard, i.e. with a precision better than 0.1 µmol/mL. The ¹³C‐isotopic enrichment of GSSG and glycine measured in the same run gave reliable values with excellent precision (standard deviation (sd) <0.3‰) and accuracy (measured between 0 and 5 APE). This novel method opens up a variety of kinetic studies with relatively low dose administration of tracers, reducing the total cost of the study design. In addition, only a minimal sample volume is required, enabling studies even in very small subjects, such as preterm infants. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthèse d'analogues bihétérocycliques du phénanthrène: Les méthyl-1-[1]benzothinéo,benzoséléno[2,3-b ]pyrroles,et méthyl-1-[1]benzofuro,benzothiéno et benzoséléno[3,2-b ]pyrroles

The condensation of ethyl sarcosinate on 2- or 3-halogeno 3- or 2-formyl[1]benzofuran. benzothiophene or benzoselenophene, and on the related 2h-[1]-3-benzoheteroyclanones is described. In the last instances the resulting compounds were formylated in teh 2-position with subsequent. After hydrolysis and decarboxylation, the I1methy][1]benzothieno-, benzoseleno [2,3-b]pyrroles were were thus obtained.     

Acylaluminum dichlorides

Evidence has been obtained for the formation of acylaluminium dichlorides by transmetalation between Cp₂Zr(Cl)(acyl) and AlCl₃. They have been shown to be reactive toward electrophiles at both the carbon and the oxygen of the acyl group.     

Complexes amines du rhodium(I) : I. Complexes du type chloro-monoamine cyclooctadiène- 1,5 rhodium(I) et leurs produits de réaction avec l''oxyde de carbone

The reaction of amines with [(RhClCod)₂] (Cod = 1,5-cyclooctadiene) gives monomeric compounds [RhCl(Am)Cod](Am = amine). Elementary analyses as well as IR and NMR spectra are consistent with their structure.On treatment with carbon monoxide at atmospheric pressure these compounds give a series of complexes, [RhCl(Am)(CO)₂], identified by elementary analyses and IR spectra.The thermolysis of [RhCl(Aam)(CO)₂] with Aam = allyamine gives [{RhCl(Aam)CO_n}] not perfectly isolated. The reaction of [{RhCl(CO)₂}₂] with 2-vinylpyridine leads to the same kind of compound [{RhCl(Vpy)CO_m}] with Vpy = 2 -vinylpyridine. This latter complex is identified by elementary analysis. The IR spectra of these two complexes show that the olefinic double bond of amines β,γ-insaturated interacts with a rhodium atom. Their properties are discussed.     

Convergence of relaxation schemes for conservation laws

We study the stability and the convergence for a class of relaxing numerical schemes for conservation laws. Following the approach recently proposed by S. Jin and Z. Xin we use a semilinear local relaxation approximation, with a stiff lower order term, and we construct some numerical first and second order accurate algorithms, which are uniformly bounded in the L^∞ and BV norms with respect to the relaxation parameter. The relaxation limit is also investigated.     

Degree of equivariant maps between generalized G-manifolds

Yasuhiro Hara in [Topology Appl. 148 (2005), 113–121] and Jan Jaworowski in [J. Fixed Point Theory Appl. 1 (2007), 111–121] studied, under certain conditions, the degree of equivariant maps between free G-manifolds, where G is a compact Lie group. The main results obtained by them involve data provided by the classifying maps of the orbit spaces. In this paper, we extend these results by replacing the free G-manifolds by free generalized G-manifolds over ${\mathbb{Z}}$ .     

Flatness Properties of S-Posets

We investigate the Galois coverings of weakly shod algebras. For a weakly shod algebra not quasi-tilted of canonical type, we establish a correspondence between its Galois coverings and the Galois coverings of its connecting component. As a consequence we show that a weakly shod algebra which is not quasi-tilted of canonical type is simply connected if and only if its first Hochschild cohomology group vanishes.     

Antidiarrhoeic effect and dereplication of the aqueous extract of Annona crassiflora (Annonaceae)

We investigated the antidiarrhoeic effect of the aqueous extract of Annona crassiflora leaves (AEAC). The AEAC decreased the diarrhoeic stools and enteropooling induced by castor oil, without altering total faecal output; moreover, the distance travelled by charcoal meal in the intestine was increased. Twenty-eight compounds were identified by LC-DAD-MS in the AEAC, including flavonoids, alkaloids and proanthocyanidins. In addition, two oligomeric series of condensed tannins of up to nine flavan-3-ol units were characterised by MALDI-MS. These data suggest that the antidiarrhoeic effect of the AEAC is related to its ability to inhibit intestinal secretion and/or to increase intestinal absorption. Moreover, the prokinetic effect of AEAC, together with its inhibitory effect on enteropooling induced by castor oil, explains why this extract decreased diarrhoeic faeces without altering the total faecal output. All these effects are in agreement with the pharmacological activity reported in the literature for many of the secondary metabolites identified.     

Structural and electronic effects in metallocene catalysts studied by x‐ray techniques

A series of metallocenes, namely, [Cp₂ZrCl₂], [(MeCp)₂ZrCl₂], [(nBuCp)₂ZrCl₂], [(iBuCp)₂ZrCl₂], [(tBuCp)₂ZrCl₂], [Et(Ind)₂ZrCl₂], [Et(IndH₄)₂ZrCl₂], and [MeSi₂(Ind)₂ZrCl₂)] were analyzed by extended x‐ray absorption fine structure (EXAFS) and x‐ray photoelectron spectroscopy (XPS). Complementary techniques, UV–vis spectroscopy and cyclic and differential pulse voltammetry, were employed to characterize the organometallic complexes. The catalysts were evaluated in ethylene polymerization, having methylaluminoxane (MAO) as the cocatalyst, and the resulting polymers were characterized by gel permeation chromatography. The structural and electronic effects caused by the coordination sphere around the metal center and their effects on the catalytic activity and polymer characteristics are discussed. Copyright © 2008 John Wiley & Sons, Ltd.