Sensitivity enhancement for the analysis of naproxen in tap water by solid-phase extraction coupled in-line to capillary electrophoresis

SPE coupled in-line to CE, as the strategy to enhance the concentration sensitivity in CE, has been used to enrich naproxen in tap water samples. In this study, a microcartridge containing an octadecyl silica (C18) sorbent was placed near the inlet within the separation capillary column. The optimum conditions were obtained when naproxen in an acidic aqueous solution (pH 3.5) was loaded into the capillary at 930 mbar for 30 min, and 20 mM ammonium acetate in methanol/water (70:30 v/v) was used as both an elution solution and a separation BGE. Under these conditions, the sensitivity was enhanced 1820-fold with respect to normal hydrodynamic injection, and the LOD achieved was 0.2 microg/L. To show the capability of the in-line SPE-CE method, tap water samples were analysed after a pretreatment consisting in an off-line C18-SPE procedure. The recovery of this procedure was higher than 80%. Under these conditions, naproxen could be detected at a concentration of 10 ng/L; so the potential of the procedure for the sensitive analysis of this type of drugs in water samples was demonstrated. Afterwards, these results were compared with those previously obtained for naproxen in water samples using different sample stacking techniques.     

Plasma surface modification of chitosan membranes: characterization and preliminary cell response studies

Surface modification of biomaterials is a way to tailor cell responses whilst retaining the bulk properties. In this work, chitosan membranes were prepared by solvent casting and treated with nitrogen or argon plasma at 20 W for 10-40 min. AFM indicated an increase in the surface roughness as a result of the ongoing etching process. XPS and contact angle measurements showed different surface elemental compositions and higher surface free energy. The MTS test and direct contact assays with an L929 fibroblast cell line indicated that the plasma treatment improved the cell adhesion and proliferation. Overall, the results demonstrated that such plasma treatments could significantly improve the biocompatibility of chitosan membranes and thus improve their potential in wound dressings and tissue engineering applications.     

An optimized luciferase bioluminescent assay for coenzyme A

A new bioluminescent method for coenzyme A (CoA) quantification is described. It is based on the enzymatic conversion of dehydroluciferyl-adenylate (L-AMP) into dehydroluciferyl-coenzyme A (L-CoA) by firefly luciferase (E.C. 1.13.12.7) (LUC), which causes a flash of light that can be measured in a luminometer. The method was subjected to optimization using experimental design methodologies to obtain optimum values for the concentrations of L-AMP ([L-AMP]), luciferase ([LUC]), ATP ([ATP]) and luciferin ([LH₂]). This method has a linear response over the range of 0.25–4 μM of CoA, with a limit of detection (LOD) of 0.24 μM and a limit of quantification (LOQ) of 0.80 μM. The assay has a relative standard deviation of about 7%. By coupling this optimized procedure to bioluminescent detection, a sensible and robust method can be obtained for the analysis of CoA.     

1H‐Indazole and 2H‐indazole derivatives of androsta‐5,16‐dien‐3β‐ol

The title compounds, 17‐(1H‐indazol‐1‐yl)androsta‐5,16‐dien‐3β‐ol, (I), and 17‐(2H‐indazol‐2‐yl)androsta‐5,16‐dien‐3β‐ol, (II), both C₂₆H₃₂N₂O, have an indazole substituent at the C17 position. The six‐membered B ring of each compound assumes a half‐chair conformation. A twist of the steroid skeleton is observed and reproduced in quantum‐mechanical ab initio calculations of the isolated molecule using a molecular orbital Hartree–Fock method. In the 1H‐indazole derivative, (I), the molecules are joined in a head‐to‐head fashion via O—H...O hydrogen bonds, forming chains along the a axis. In the 2H‐indazole derivative, (II), the molecules are joined in a head‐to‐tail fashion with one of the N atoms of the indazole ring system acting as the acceptor. The hydrogen‐bond pattern consists of zigzag chains running along the b axis. Substituted steroids have proven to be effective in inhibiting androgen biosynthesis through coordination of the Fe atoms of some enzymes, and this study shows that indazole‐substituted steroids adopt twisted conformations that restrict their intermolecular interactions.     

5α‐Androst‐3‐en‐17‐one oxime

The title compound, C₁₉H₂₉NO, is a C17‐oxime derivative of a potent aromatase inhibitor, which surprisingly has been found to have no inhibitory power. It crystallizes with two independent molecules in the asymmetric unit. C=N—O—H...N hydrogen bonds link pairs of molecules to form dimers almost parallel to the bc plane. Cohesion of the structure is also due to another three C—H...O hydrogen bonds directed along the a axis. This hydrogen‐bonding scheme can be correlated to the almost complete loss of inhibitory power of the title compound.     

Integral stable manifolds in Banach spaces

We establish the existence of smooth integral stable manifoldsfor sufficiently small perturbations of nonuniform exponentialdichotomies in Banach spaces. We also consider the case of anonautonomous dynamics given by a sequence of C¹ maps. The optimalsmoothness of the manifolds is obtained at the same time astheir existence, using a convenient lemma of Henry. Furthermore,we obtain not only the exponential decay of the dynamics alongthe stable manifolds, but also of its derivative. In addition,we give a characterization of the stable manifolds in termsof the maximal exponential growth rate that is allowed, we discusshow the manifolds vary with the perturbations, and we discusstheir equivariance with respect to a sequence of linear operators.     

Botanical Characterization of Guiera senegalensis Leaves

Guiera senegalensis J. F. Gmel. (Combretaceae) is one of the most important West African medicinal plants, often used to treat a variety of microbial infections. The most frequently used plant part is the leaf, its medicinal use being corroborated by several in vitro antimicrobial activity studies. However, quality criteria for pharmaceutical use, including botanical identification, are not yet determined. Aiming the establishment of such criteria, the present work deepens today's knowledge on G. senegalensis leaf morphology and anatomy, the anatomical characters of both leaf transversal section and powdered leaves being hereby presented for the first time. The most useful characters for identification purposes are leaf isobilateral organization, with similar upper and lower surfaces and a palisade parenchyma on both surfaces; trichome insertion points on both epidermis, surrounded by polar arrangements of cells; tomentose indumentum on the upper epidermis consisting of compartmented and uniseriated trichomes with long, curved, or straight terminal cells; brown scales, isolated or inserted into the epidermis, formed by radially arranged cells surrounding a central cell, with a more or less circular form and a conspicuous base; calcium oxalate cluster crystals, isolated or inserted into the palisade parenchyma and absent in lateral veins.     

A quantum mechanical strategy to investigate the structure of liquids: the cases of acetonitrile, formamide, and their mixture

A computational strategy based on quantum mechanical (QM) calculations and continuum solvation models is used to investigate the structure of liquids (either neat liquids or mixtures). The strategy is based on the comparison of calculated and experimental spectroscopic properties (IR-Raman vibrational frequencies and Raman intensities). In particular, neat formamide, neat acetonitrile, and their equimolar mixture are studied comparing isolated and solvated clusters of different nature and size. In all cases, the study seems to indicate that liquids, even when strongly associated, can be effectively modeled in terms of a shell-like system in which clusters of strongly interacting molecules (the microenvironments) are solvated by a polarizable macroenvironment represented by the rest of the molecules. Only taking into proper account both these effects can a correct picture of the liquid structure be achieved.     

One-electron reduction of superoxide radical-anions by 3-alkylpolyhydroxyflavones in micelles. Effect of antioxidant alkyl chain length on micellar structure and reactivity

In micellar solutions, one-electron reduction of (*)O 2 (-) radical-anions by 3-alkylpolyhydroxyflavones (FnH) with alkyl chains of n = 1, 4, 6, 10 carbons produces phenoxyl radicals ( (*)Fn) identical to those obtained by one-electron oxidation by (*)Br 2 (-) radical-anions or by repair of tryptophan radicals. In cetyltrimethylammonium bromide (CTAB), F1H localizes in the Stern layer, and alkyl chains of other FnH solubilize in the hydrophobic interior, interacting with cetyl tails. This interaction produces more compact micelles with lower intramicellar fluidity, as suggested by the increase in the pseudo-first-order rate constant of (*)Fn formation ( k 1) from approximately 390 s (-1) for n = 1 to 610 s (-1) for n = 10, leading to an intramicellar bimolecular rate constant of 1 x 10 (5) M (-1) s (-1). Additionally, (*)F1 and (*)F4 decay by intermicellar bimolecular reaction (2 k = 20 and 2 x 10 (5) M (-1) s (-1), respectively) whereas other (*)Fn radicals are stable over seconds due to increased localization with regards to the Stern layer. In contrast, the thick uncharged hydrophilic palisade layer and the compact hydrophobic core of Triton X100 micelles are responsible for a much higher microviscosity resulting in a decrease in k 1 from approximately 15.6 s (-1) for n = 1 to 9.6 s (-1) for n = 10.