Influence of sialic acid and bacterial sialidase on differential adhesion of Pseudomonas aeruginosa to epithelial cells

Epithelial cell lines from several tissues show a differential sensitivity to Pseudomonas aeruginosa adherence. A549 (lung), HepG2 (liver) and Caco-2 (colon) cells presented an adhesion index of about 3, 1.5 and 5 CFU/cell, respectively, whereas Mz-Ch cell lines (gallbladder cholangiocytes) presented adhesion indexes up to 35. These variations could be associated with the variable amount of sialic acid in cell surface glycoconjugates. Moreover, the presence of free sialic acid in culture media induces the secretion by P. aeruginosa of a sialidase which is able to hydrolyze glycoconjugate-linked sialic acid. As shown with A549 cells, this specific hydrolysis increases bacterial adhesion, probably by unmasking new binding sites onto the cell surface.     

Polyvinyl‐Locked versus Free Quaterthiophene: Effect of Spatial Constraints on the Electronic Properties of n‐Hexylquaterthiophene

A soluble, low‐weight fraction of poly(α‐vinyl,ω‐n‐hexyl‐quaterthiophene), PT4Hex, having n‐hexylquaterthiophenes as side‐chain groups, is prepared by free‐radical polymerization of α‐vinyl,ω‐n‐hexyl‐quaterthiophene and the corresponding properties compared to those of free di‐n‐hexylquaterthiophene (T4Hex). Optical analysis (absorption and emission) and X‐ray diffraction data indicate that in the polyvinyl‐locked architecture the quaterthiophene pendants adopt a cofacial arrangement with a mutual distance close enough for π–π orbitals to overlap (～4 Å). As a consequence of the close chain packing, a shift of the reduction potential of about 0.5 V toward less negative values with respect to free T4Hex, is found for PT4Hex films. Due to its enhanced electron affinity, PT4Hex displays an electron‐acceptor behavior when blended with alkylated and silylated quaterthiophenes acting as donors.     

Preparation of a novel polystyrene-based urea resin

A urea-functionalized polystyrene-resin with a Rink linker was prepared by adaptation of a solution-phase synthesis to solid-phase chemistry. Thereby, a resin-bound acylurea was formed by reacting a Rink-amide resin with trichloroacetyl isocyanate, followed by the thermal removal of the trichloroacetyl group and thus generating the unsubstituted solid-supported urea.     

Self-assembly of nanoscale supramolecular truncated tetrahedra

Two nanoscale truncated tetrahedra were synthesized via Pt(II)-mediated self-assembly. The first resulted from the reaction of 3 equiv of cis-Pt(PMe3)2(OTf)2 and 2 equiv of 1,3,5-tris(4-pyridylethynyl)benzene, giving a truncated tetrahedron with a diameter of approximately 25 A. The second, analogous structure was obtained by the self-assembly of cis-Pt(PMe3)2(OTf)2 and 1,3,5-tris(4-pyridyl-trans-ethenyl)benzene. These two truncated tetrahedra were crystallized after partially exchanging the counterion to cobalticarborane for the X-ray structural analysis.     

Quantification of the plant-derived hallucinogen Salvinorin A in conventional and non-conventional biological fluids by gas chromatography/mass spectrometry after Salvia divinorum smoking

A gas chromatography method with mass spectrometric detection is described for the determination of Salvinorin A, the main active ingredient of the hallucinogenic mint Salvia divinorum. The method was validated in plasma, urine, saliva and sweat using 17-alpha-methyltestosterone as internal standard. The analytes were extracted from biological matrices with chloroform/isopropanol (9:1, v/v). Chromatography was performed on a 5% phenyl methyl silicone capillary column and analytes were determined in the selected ion monitoring mode. The method was validated over the concentration range 0.015-5 microg/mL plasma, urine and saliva and 0.01-5 microg/patch in the case of sweat. Mean recoveries ranged between 77.1 and 92.7% for Salvinorin A in different biological matrices, with precision and accuracy always better than 15%. The method was applied to the analysis of urine, saliva and sweat from two consumers after smoking 75 mg plant leaves to verify the presence of the active ingredient of S. divinorum in human biological fluids as a biomarker of plant consumption. Salvinorin A was detected in urine (2.4 and 10.9 ng/mL) and saliva (11.1 and 25.0 ng/mL), but not in sweat patches from consumers.     

Membrane-assisted solvent extraction of seven phenols combined with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) was applied for the determination of seven phenols (phenol, 2-chlorophenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 4-chloro-3-methylphenol, 2,4,6-trichlorophenol and pentachlorophenol) with log Kow (octanol-water-partition-coefficient) between 1.46 (phenol) and 5.12 (pentachlorophenol) in water. The extraction solvents cyclohexane, ethyl acetate and chloroform were tested and ethyl acetate proved to be the best choice. The optimisation of extraction conditions showed the necessity of adding 5 g of sodium chloride to each aqueous sample to give a saturated solution (333 g/L). The pH-value of the sample was adjusted to 2 in order to convert all compounds into their neutral form. An extraction time of 60 min was found to be optimal. Under these conditions the recovery of phenol, the most polar compound, was 11%. The recoveries of the other analytes ranged between 42% (2-chlorophenol) and 98% (2,4-dichlorophenol). Calibration was performed using large volume injection (100 microL injection volume). At optimised conditions the limits of detection were between 0.01 and 0.6 microg/L and the relative standard deviation (n = 3) was on average about 10%. After the method optimisation with reagent water membrane-assisted solvent extraction was applied to two contaminated ground water samples from the region of Bitterfeld in Saxony-Anhalt, Germany. The results demonstrate the good applicability of membrane-assisted solvent extraction for polar analytes like phenols, without the necessity of derivatisation or a difficult and time-consuming sample preparation.     

Photochromic properties of thienylpyrrole azo dyes in solution

The photochromic behaviour of thienylpyrrole azo dyes in THF solutions was studied for the first time. The photochromic properties are strongly dependent on the substitution pattern on the dyes. Nitro-substituted thienylpyrrole azo dyes are particularly interesting since they exhibit very fast colouration/decolouration processes. The activation energies of these compounds are among the lowest values reported for heterocyclic azo dyes. These compounds show aggregation phenomena in freshly prepared solutions of THF, which lead to variable photochromic behaviours. Only after 1-5 h the solutions reach equilibrium and then reproducible photochromic behaviour can be observed.     

Solubility of Propene in Water and in a Mineral Medium for the Cultivation of a XanthobacterStrain

Solubility measurements of propene in water at atmospheric pressure and at thirteen temperatures in the range 293.15–323.15 K were carried out with a precision of 0.3%, using an apparatus based on the saturation method. The mole fractions, at a gas partial pressure of 101.325 kPa, were fitted to a Clarke–Glew–Weiss equation, which was used to calculate the standard molar Gibbs energy, enthalpy, and entropy changes for the process of transferring the propene molecules from the gaseous to the water phase. Solubility measurements of propene in the growth medium ofXanthobacter Py2 at 298.15, 303.15, and 308.15 K were also carried out at atmospheric pressure. These experimental data, expressed in Ostwald coefficients at the total pressure of 101.325 kPa, were about 2% lower than their water counterparts.     

Convergent Synthesis of Naphthylisoquinoline Alkaloids: Total Synthesis of (+)-O-Methylancistrocline

A highly convergent synthesis of the methyl ether derivative 2a of the naphthylisoquinoline alkaloid ancistrocline (2) is described. The key step involves a stereoselective biaryl coupling between the chiral oxazoline 3 and the Grignard reagent 4 derived from the optically active tetrahydroisoquinoline 8. The atropisomeric mixture was then converted to the separable acetamides 11 and 12, which were obtained in a ratio of 16:84 and an overall yield of 32% for the three steps. The major atropisomer 12 was then converted into O-methylancistrocline (2a), which was identical to a semisynthetic sample derived from the related alkaloid ancistrocladinine (14).     

Anion Controlled Supramolecular Self‐Assembly of Tetraprotonated Tris[2‐(benzylamino)ethyl]amine

The novel supramolecular assembly of composition [{(bz₃tren)H₄}⁴⁺ · (ReO₄)^— · 3(Cl)^—] resulted from the self‐organization of a mixture of tris[2‐(benzylamino)ethyl]amine (bz₃tren), HCl and NH₄ReO₄ at a molar ratio of 1:4.7:1 in methanol. The crystal architecture is characterized by stacks of repeating sandwich‐type building blocks that contain charge‐assisted N—H···O(Re) hydrogen bonds [N···O 2.81‐2.86Å] and weaker C—H···O(Re) interactions [C···O 3.11Å]. The stacks are further linked by N—H···Cl [N···Cl 3.03Å] and weaker C—H···Cl [C···Cl 3.47‐3.74Å] interactions into two‐dimensional layers bordered by the benzyl groups of the [(bz₃tren)H₄]⁴⁺ cations. Edge‐to‐face C—H···π interactions involving the aromatic rings occur within and between the layers. The protonation constants of bz₃tren in methanol were determined by potentiometric titration. The corresponding structures of the ligand in its different protonation states were calculated at the DFT‐level.