Stereoselective Synthesis of Novel Diels–Alder Adducts of p-Substituted Methyl Thiocinnamates and Cyclopentadiene

This article describes the Diels–Alder reaction between methyl thiocinnamates, substituted at the para position by electron-donating and electron-withdrawing groups, with cyclopentadiene in the presence of catechol boron bromide (CBB) as a Lewis acid catalyst. The adduct configuration was confirmed by ¹H NMR coupling constants and single-crystal x-ray diffraction. Total endo stereoselectivity was observed in all reactions and was attributed to the effective secondary interaction between the boron atom and the incipient double bond in the norbonene resulting from the planar geometry of the catalyst. ¹³C NMR chemical shifts of the coordinated dienophile carbonyl carbons with CBB compared to those of the non coordinated thiocinammates suggest a strong complexation with the catalyst.     

Rhamnolipid emulsifying activity and emulsion stability: pH rules

Rhamnolipids have excellent emulsifying power with a variety of hydrocarbons, aromatic compounds and vegetable oils. This paper evaluates the effect of pH ranging from 3 to 9 on the emulsifying activity and stability of rhamnolipids and hydrophobic substrates (benzene, soybean oil and kerosene). Sodium dodecyl sulfate was used as a reference to compare the level of chemical and biological surfactant activity after 24 h (E(24)). The results indicate that pH exerts an influence over emulsion formation and stability. For rhamnolipids, peak emulsifying activity occurred under base conditions for all substrates, with the highest value achieved with kerosene at pH 8. The results of the present study demonstrate that rhamnolipids could replace chemical surfactants, such as SDS, in different industrial fields.     

Spin Seebeck coefficient of a molecular spin pump

Within a generalized version of previously considered model of a molecular spin pump controlled by an external electric field [J. Fransson and M. Galperin, Phys. Rev. B, 2010, 81, 075311] we discuss thermal properties of such spintronic devices. The spin Seebeck coefficient of a molecular spin pump is introduced, and several possible definitions of a nonequilibrium Seebeck coefficient are discussed. The influence of inelastic effects in spin transport on its thermospintronic characteristics are demonstrated within numerical examples.     

Isoswertisin flavones and other constituents from Peperomia obtusifolia

A phytochemical investigation of the leaves and stems of Peperomia obtusifolia (Piperaceae) yielded a new flavone C-diglycoside isoswertisin-4'-methyl-ether-2'α-L-rhamnoside (1), along with four known compounds: isoswertisin-2'α-L-rhamnoside (2), (+)-diayangambin (3), 2-episesalatin (4) and corchoionoside C (5). The structures of the two flavone C-diglycosides (1, 2) were elucidated on the basis of 1D and 2D NMR spectroscopy and MS spectrometric data. These flavones were evaluated by bioautographic assay against Cladosporium cladosporioides and C. sphaerospermum and showed weak antifungal activity.     

Development and in-house validation of allergen-specific ELISA tests for the quantification of Dau c 1.01, Dau c 1.02 and Dau c 4 in carrot extracts (<Emphasis Type="Italic">Daucus carota</Emphasis>)

Even though carrot allergy is common in Europe, the amount of different allergens in carrots is still unknown due to a lack of methods for quantitative allergen measurements. The current study aimed at the development of quantitative ELISA tests for the known carrot allergens, namely Dau c 1.01, Dau c 1.02, and Dau c 4 in pure carrot extracts. Monoclonal antibodies targeting the major carrot allergen isoforms Dau c 1.01 and Dau c 1.02 were generated and combined in sandwich ELISA with rabbit antisera against Api g 1, the celery homologue of Dau c 1. A competitive ELISA for the carrot profilin Dau c 4 was based on a polyclonal rabbit antiserum. The three ELISA tests were allergen-specific and displayed detection limits between 0.4 and 6 ng allergen/ml of carrot extract. The mean coefficient of variation (CV) as a means of intraassay variability of the Dau c 1.01, Dau c 1.02 and Dau c 4 ELISA tests was 8.1%, 6.9%, and 11.9%, and the mean interassay CV 13.3%, 37.1% and 15.6%, respectively. Target recovery ranged between 93 and 113%. In conclusion, the specific, accurate and reproducible quantification of three important carrot allergens may help to identify less allergenic carrot varieties, as well as to standardize the amount of allergens in extracts used for carrot allergy diagnosis.     

Continuous full filling capillary electrochromatography-electrospraying chromatographic nanoparticles

The influence of instrumental parameters affecting the ionization in continuous full filling capillary electrochromatography/electrospray ionization mass spectrometry (CFF‐CEC/ESI‐MS) was investigated. The investigated parameters were the BGE and sheath liquid ion strength and organic modifier content, the nebulizer gas pressure, and the concentration of nanoparticles in the BGE. It was found that the nebulizer pressure had the largest influence on the separation efficiency and apparent retention. It was shown that even the lowest pressure investigated was sufficient to guide the nanoparticle flow away from the mass spectrometer inlet. A nebulizer pressure of 5 psi was found to be optimal; increasing the pressure significantly decreased the separation efficiency due to the generation of a hydrodynamic flow. Generally, the ion strength of both the BGE and the sheath liquid were found to have very moderate effects on the separation of a homologous series of dialkyl phthalates, whereas the ionization efficiency was found to be unaffected by the nanoparticles and the separation efficiency was found to increase with increasing concentrations up to 3.8 mg/mL, whereafter it was observed to drop. The optimized method was linear over a wide concentration range and presented LOD and LOQ more than threefold lower than those previously reported using CFF‐CEC/ESI‐MS.     

Optimizing the extraction, separation and quantification of tricyclic antidepressant drugs in human plasma with CE-ESI-TOF-MS using cationic-coated capillaries

In this study, the extraction and CE-ESI-TOF-MS analysis of tricyclic antidepressant (TCA) drugs imipramine, desipramine, clomipramine and norclomipramine in human plasma has been optimized. The CE capillaries were modified with ω-iodo-alkyl ammonium salt (M7C4I coating) to reduce analyte adsorption to the silica wall. The use of a strong cation exchange (SCX) solid-phase extraction (SPE) column specifically designed for the extraction of basic drug species from biofluids gave very clean extracts with high and reproducible recoveries. The extraction recoveries were ranging between 87 and 91% with % RSD values of 0.5-1.7% (n=3). The obtained strong cation exchange-SPE extracts of the TCA in human plasma only contained the analytes of interest. The optimized CE separation conditions were obtained by adding ACN and acetic acid to the sample while using an aqueous BGE. The CE-ESI-TOF-MS analysis was performed within 6 min for all TCA analytes under the optimized condition with peak efficiencies up to 1.4 x 10? plates/m and an average % RSD of the migration times of the analytes of 0.3% (n=5). The presented method can readily be used for the extraction and quantification of basic drug species in human biological fluids and in pharmaceutical formulations.     

Spectroscopic properties of a perfluorinated ketone for PLIF applications

This work identifies the fluorescence characteristics of a perfluorinated ketone, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, further referred to as fluoroketone. This compound is suitable for use with the third harmonic of an Nd:YAG laser for quantitative concentration measurements, as it exhibits strong emission even for relatively low excitation and has a near-linear response of fluorescence intensity with concentration. This makes it suitable for a broad range of fluorescence applications. The absorption cross-section of 3.81 × 10⁻¹⁹ cm² was found to be constant for a temperature range of 293–441 K and a pressure range of 1–18 atm. A calibration line has been generated that relates the concentration of gaseous and liquid fluoroketone with its absorption coefficient.     

Controlled‐Atmosphere Flame Fusion Single‐Crystal Growth of Non‐Noble fcc,hcp, and bcc Metals Using Copper,Cobalt, and Iron

The growth of noble‐metal single crystals via the flame fusion method was developed in the 1980s. Since then, there have been no major advancements to the technique until the recent development of the controlled‐atmosphere flame fusion (CAFF) method to grow non‐noble Ni single crystals. Herein, we demonstrate the generality of this method with the first preparation of fcc Cu as well as the first hcp and bcc single crystals of Co and Fe, respectively. The high quality of the single crystals was verified using scanning electron microscopy and Laue X‐ray backscattering. Based on Wulff constructions, the equilibrium shapes of the single‐crystal particles were studied, confirming the symmetry of the fcc, hcp, and bcc single‐crystal lattices. The low cost of the CAFF method makes all kinds of high‐quality non‐noble single crystals independent of their lattice accessible for use in electrocatalysis, electrochemistry, surface science, and materials science.     

Completing the Redox-Series of Silicon Trisdioxolene: ortho-Quinone and Lewis Superacid Make a Powerful Redox Catalyst

Quinones are mild oxidants, the redox potentials of which can be increased by supramolecular interactions. Whereas this goal has been achieved by hydrogen bonding or molecular encapsulation, a Lewis acid-binding strategy for redox amplification of quinones is unexplored. Herein, the redox chemistry of silicon tris(perchloro)dioxolene 1 was studied, which is the formal adduct of ortho-perchloroquinone Q^Cl with the Lewis superacid bis(perchlorocatecholato)silane 2 . By isolating the anionic monoradical 1 ^{. −} , the redox-series of a century-old class of compounds was completed. Cyclic voltammetry measurements revealed that the redox potential in 1 was shifted by more than 1 V into the anodic direction compared to Q^Cl , reaching that of “magic blue” or NO⁺. It allowed oxidation of challenging substrates such as aromatic hydrocarbons and could be applied as an efficient redox catalyst. Remarkably, this powerful reagent formed in situ by combining the two commercially available precursors SiI₄ and Q^Cl .