Quantification of fenitrothion and its main metabolites in poplar leaves by isotope dilution gas chromatography-mass spectrometry coupled with solid-phase microextraction

A sensitive and specific method for determining fenitrothion and its main metabolites, 3-methyl-4-nitrophenol and fenitrooxon, in poplar leaves using deuterated isotopes as the internal standard is described. The analytes and the labeled isotopes were extracted from leaves by solid-phase microextraction and subsequently analysed by gas chromatography coupled with mass spectrometry. The method had a chromatographic run time of 17.0 min and good linearity over the range 0.01-10 mg kg(-1). The detection limits ranged between 2.5 and 0.6 microg kg(-1). The isotopic dilution technique allowed improving significantly the repetitivity even using different fibers with the same coating (RSD<5.1%). The method was applied successfully to study the persistence of fenitrothion in forestal matrices in a poplar forest after cannon spray application of the insecticide.     

Correlation and prediction of partition coefficient between the gas phase and water, and the solvents dry methyl acetate, dry and wet ethyl acetate, and dry and wet butyl acetate

Experimental partition coefficient data have been compiled from the published literature for the water/methyl acetate, water/ethyl acetate and water/butyl acetate partition systems, log P data, and for the gas/methyl acetate, gas/ethyl acetate and gas/butyl acetate partition systems, log K data. Application of the Abraham solvation parameter model to the sets of partition coefficients leads to equations that correlate the log P data and log K data to 0.18 log units for the three dry alkyl acetate solvents. Slightly larger deviations were noted for solute partition into both wet ethyl acetate and wet butyl acetate. The derived correlations were validated using training set and test set analyses.     

Poly‐l‐Lactic Acid Nanofiber–Polyamidoamine Hydrogel Composites: Preparation,Properties, and Preliminary Evaluation as Scaffolds for Human Pluripotent Stem Cell Culturing

Electrospun poly‐l ‐lactic acid (PLLA) nanofiber mats carrying surface amine groups, previously introduced by nitrogen atmospheric pressure nonequilibrium plasma, are embedded into aqueous solutions of oligomeric acrylamide‐end capped AGMA1, a biocompatible polyamidoamine with arg‐gly‐asp (RGD)‐reminiscent repeating units. The resultant mixture is finally cured giving PLLA‐AGMA1 hydrogel composites that absorb large amounts of water and, in the swollen state, are translucent, soft, and pliable, yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant, since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds, the composites prove capable of maintaining short‐term undifferentiated cultures of human pluripotent stem cells in feeder‐free conditions.

     

Studies toward the total synthesis of axinellamine and massadine

Intramolecular Diels-Alder reactions of several N-O linked 4-vinylimidazole dimers provide the expected adduct in moderate to good yield as a single, all trans stereoisomer, along with smaller amounts of the inverse electron demand adduct. Oxidative rearrangement of the cycloadducts occurs on treatment with Davis' reagent, providing a single spiro imidazolone in good yield and with excellent levels of stereocontrol albeit epimeric at the spiro center found in axinellamine and massadine.     

Simple and rapid determination of biogenic amines in wine by liquid chromatography-electrospray ionization ion trap mass spectrometry

A rapid liquid chromatographic-electrospray ionisation ion trap mass spectrometry (LC-ESI-ITMS) method has been developed for the routine analysis of eight of the most oenologically important biogenic amines in wine without any sample pre-treatment. The method involves addition of heptylamine as an internal standard (IS) and the direct injection of filtered wine samples previously diluted with ultra high purity (UHP) water. The full-scan MS-MS spectra and the identical retention times to those of reference standards were used for unequivocal identification of the analytes. For most amines, the most abundant ions were derived from the loss of an ammonia group, while in the case of spermine and the I.S. the major product ions arose from the loss of 1,3-propyldiamine and the production of adduct with water, respectively. Detection was achieved in positive ionisation with an ion trap mass spectrometer operating in multiple-reaction monitoring (MRM) mode. The method allowed accurate determination of the analytes in the range 0.5-40 ng mL⁻¹. Within-day and between-day relative standard deviation percentages were <8% and <12%, respectively. The overall process was successfully applied to identify and quantify biogenic amines in Rioja red wines. The new method is sensitive, rapid, cheap and less labour intensive.     

Thalidomide analogs from diamines: Synthesis and evaluation as inhibitors of TNF-alpha production

Fourteen thalidomide analogs bearing two phthalimido units were prepared in high yields (83-94%) by condensation of different diamines with phthalic or 3-nitrophthalic anhydride. An in vitro investigation of the compounds as inhibitors of the TNF-alpha production was performed. The inhibition was higher for compounds bearing amino and nitro groups and was modulated by increasing the size of the spacers between the phthalimide groups.     

Influence of the support and precursor compounds on the sintering and coking of supported nickel oxyreforming catalysts

In this paper the activity, selectivity and mainly stability of nickel catalysts in the oxyreforming reaction are analyzed. The catalysts were prepared employing different precursors (nickel nitrate and nickel acetylacetonate) on α-Al₂O₃ and α-Al₂O₃ modified by a layer of aluminium oxide. The catalytic sample obtained from nickel acetylacetonate on the modified support showed the best stability.     

Effects of NR1 splicing on NR1/NR3B-type excitatory glycine receptors

Background  

N-methyl-D-aspartate receptors (NMDARs) are the most complex of ionotropic glutamate receptors (iGluRs). Subunits of this subfamily assemble into heteromers, which – depending on the subunit combination – may display very different pharmacological and electrophysiological properties. The least studied members of the NMDAR family, the NR3 subunits, have been reported to assemble with NR1 to form excitatory glycine receptors in heterologous expression systems. The heterogeneity of NMDARs in vivo is in part conferred to the receptors by splicing of the NR1 subunit, especially with regard to proton sensitivity.