Quantitation of imidazo[1,2‐a]quinoxaline derivatives in human and rat plasma using LC/ESI‐MS

Since several years, our group developed quinoxalinic compounds. Among the synthesized compounds, in the imidazo[1,2‐a]quinoxaline series, EAPB0203 has shown interesting activities both on melanoma and lymphoma. The structure of EAPB0203 has been modulated and a new compound, EAPB0503, exhibits an in vitro cytotoxic activity on melanoma cancer cell line 7–9 times higher than EAPB0203. We validated an LC/ESI‐MS method to simultaneously quantify EAPB0503 and its metabolite EAPB0603 in human and rat plasma. Chromatography was performed on a C8 Zorbax eclipse XDB column with a mobile phase consisting of acetronitrile and formate buffer gradient elution. LC‐MS data were acquired in SIM mode at m/z 305, 291, and 303 for EAPB0503, EAPB0603, and the internal standard, respectively. The drug/internal standard peak area ratios were linked via quadratic relationships to concentrations (low range: 5–300 μg/L, high range: 100–1000 μg/L). The method is precise (precision, ?14%) and accurate (recovery, 92–113%). Mean extraction efficiencies, >72% for each analyte, were obtained. The lower LOQs were 5 μg/L. This highly specific and sensitive method was successfully used to investigate plasma concentrations of EAPB0503 and EAPB0603 in a pharmacokinetic study carried out in rat and would also be useful in clinical trials at a later stage.     

Enantioselective addition of oxindoles to aliphatic α,β-unsaturated aldehydes

A highly enantioselective organocatalytic oxindole addition to α,β-unsaturated aldehydes is reported. The reaction is catalyzed by simple and commercially available chiral secondary amines, affording the corresponding adducts with good yields and with moderate diastereoselectivities.     

Full-field XRF instrument for cultural heritage: Application to the study of a Caillebotte painting

A novel full-field X-ray fluorescence spectrometer developed for cultural heritage applications is presented. Named “CartiX,” it was designed for routine deployment in the field (museum, archeological site) and uses a concept under development at NASA for planetary exploration. CartiX utilizes 2 miniature X-ray tubes, a square pore Micro-channel Plate X-ray Optic, and a direct-illumination CCD camera to collect spatially resolved X-ray fluorescence data from an area of 13 x 13 mm². We report here the application of CartiX to the analysis of a Gustave Caillebotte painting directly in the exhibition room. The Impressionists are renowned for their painting technique and their approach in capturing the effects of light in nature through a new use of color. They adopted innovative artistic practices consisting of short brushstrokes of unmixed colors that barely convey forms and give an effect of spontaneity and effortlessness that masks their often carefully constructed compositions. Here, we use high spatial resolution chemical data measured with CartiX to reveal the artist's complex use of pigments and the formation of alteration products and to help in the interpretation of the artist's choice of materials and their manipulation with small and thin brushstrokes.     

The Methyldiphenylsilylation of Carboxylic Acid Dianions1

The direct C-(methyldiphenylsilylation) of carboxylic acid dianions is reported.     

Synthesis of Furoates and Furfurylic Alcohol Esters Under Very Mild Conditions Using Supported Base Catalysis

Sym-phthaloyl chloride under controlled cathodic reduction is converted into trans-[1(3H)-isobenzofuranone, 3-(3-oxo-1(3H)-isobenzofuranylidene)]: trans-biphthalyl in 65% yield.     

The colourful feasibility problem

We study a colourful generalization of the linear programming feasibility problem, comparing the algorithms introduced by Bárány and Onn with new methods. This is a challenging problem on the borderline of tractability, its complexity is an open question. We perform benchmarking on generic and ill-conditioned problems, as well as recently introduced highly structured problems. We show that some algorithms can lead to cycling or slow convergence and we provide extensive numerical experiments which show that others perform much better than predicted by complexity arguments. We conclude that the most efficient method is a proposed multi-update algorithm.     

Isomorphisms of one-relator semigroup algebras

All isomorphisms between comutative semigroup algebras K[S] and K[T] are found when K is a field and S, T have two generators subject to a single homogeneous defining relation     

Bodily variability of zinc natural isotope abundances in sheep

Evidence is growing that the range of zinc stable isotope compositions, represented by the deviation of ⁶⁶Zn in permil units relative to a standard and expressed as δ⁶⁶Zn, is larger in organic matter than in inorganic material. This study reports the variations of δ⁶⁶Zn in various organs of sheep raised on a controlled diet. Zinc was purified by anion‐exchange chromatography. The Zn concentrations and Zn stable isotope compositions were determined by quadrupole inductively coupled plasma mass spectrometry and multi‐collector inductively coupled plasma mass spectrometry, respectively. The data show that δ⁶⁶Zn variability exceeds 1‰, with bone, muscle, serum and urine enriched in the heavy isotopes, and feces, red blood cells, kidney and liver enriched in light isotopes, all relative to the diet value. The ⁶⁶Zn enrichment of the circulating serum reservoir is likely to take place in the digestive tract, probably through the preferential binding of lighter isotopes with phytic acid, which is known to control the uptake of metallic elements. Mass balance calculations suggest that the ⁶⁶Zn depletion between diet and feces, which is not balanced by any other outward flux, leads to a secular isotopic drift in serum. A simple time‐dependent two‐box model, involving the gastro‐intestinal tract on the one hand and the muscle and bone on the other, predicts that the maximum ⁶⁶Zn enrichment, which equals the difference in δ⁶⁶Zn between diet and bulk (～0.25‰), is reached after about ten years. Therefore, a better understanding of the variations of natural abundance of Zn isotopes in animals and humans will probably bring new perspectives for the assessment of their Zn status. Copyright © 2010 John Wiley & Sons, Ltd.     

Noncommutative Dynamical Models with Quantum Symmetries

We define dynamical models on the q-Minkowski space algebra (which is a particular case of the Reflection Equation Algebra) as deformations (quantizations) of dynamical models with rotational symmetries, and we find their integrals. In particular, we introduce a q-analog of the Runge-Lenz vector and a q-analog of the dynamics in space-time with a spherically symmetric metric.