Study of the interactions between phenolic compounds and micellar media using micellar solid-phase microextraction/gas chromatography

Solid-phase microextraction coupled to gas-chromatography with mass-spectrometry detection has been employed to establish the sensitivity indexes as well as to study the partition coefficients of phenols into ionic and nonionic micelles. The sensitivity indexes values can be used to estimate qualitatively the affinity between phenols and micelles. The studied phenols, some of them with high environmental interest, include chloro-, alkyl-, and methoxy-phenols. The results obtained in this work, using 85 microm polyacrylate fiber and anionic (sodium dodecyl sulphate), cationic (cetyltrimethylammonium bromide), and nonionic (Triton X-100 and polyoxyethylene-10-lauryl ether) surfactants, indicate that SPME is a viable method for estimating the micelle partition coefficients.     

Coupling of internal alkynes in tp(me2)ir derivatives: selective oxidation of a noncoordinated double bond of the resulting iridacycloheptatrienes

The reaction of different Tp(Me2)Ir derivatives and dimethylacetylene dicarboxylate (DMAD) allows the preparation of three different metallacycloheptatriene complexes and an unusual allyl-terminated metallacycle. The C atoms of distant C=C bonds in the metallacycles, including aromatic ones, can be converted selectively to the corresponding keto functionality under mild conditions.     

Surfactant solvation effects and micelle formation in ionic liquids

The formation of micelles in 1-butyl-3-methyl imidazolium chloride (BMIM-Cl) and hexafluorophosphate (BMIM-PF6) were explored using different surfactants and the solvation behavior of the new micellar-ionic liquid solutions examined using inverse gas chromatography.     

Determination of the Association Constant of 6-Thiopurine and Chitosan Grafted β-Cyclodextrin

The equilibrium constants (K) for the inclusion complex formationof -cyclodextrin (-CD) with Methyl Orange (MO) and substituted azoanilinium chlorides were determinedspectrophotometrically. Based on the results, the substituent effecton the inclusion complexation of -CD with azoanilinium chlorides was discussed indetail. Further, the solvent effects on the inclusion complexation of MO with -CD andheptakis(2,6-di-O-methyl)--cyclodextrin (DM--CD) wereexamined in aqueous organic mixtures with water-miscible organic compounds(dimethylsulfoxide, acetonitrile, N,N-dimethylformamide, and acetone). It was found that the K value for the inclusion complexformation with -CD and DM--CD decreases remarkably with increasing ratioof organic solvents, dependent of the surface tension of solvent mixtures.     

Rocking ratchets in two-dimensional Josephson networks: collective effects and current reversal

A detailed numerical study on the directed motion of ac-driven vortices and antivortices in 2D Josephson junction arrays with an asymmetric periodic pinning potential is reported. dc-voltage rectification shows a strong dependence on vortex density as well as an inversion of the vortex flow direction with ac amplitude for a wide range of vortex density around f = 1/2 (f = Ha(2)/Phi(0)), in good agreement with recent experiments by Shalóm and Pastoriza [Phys. Rev. Lett. 94, 177001 (2005)10.1103/PhysRevLett.94.177001]. The study of vortex structures, spatial and temporal correlations, and vortex-antivortex pairs formation gives insight into a purely collective mechanism behind the current reversal effect.     

Tuning the Nanoaggregates of Sialylated Biohybrid Photosensitizers for Intracellular Activation of the Photodynamic Response

In the endeavor of extending the clinical use of photodynamic therapy (PDT) for the treatment of superficial cancers and other neoplastic diseases, deeper knowledge and control of the subcellular processes that determine the response of photosensitizers (PS) are needed. Recent strategies in this direction involve the use of activatable and nanostructured PS. Here, both capacities have been tuned in two dendritic zinc(II) phthalocyanine (ZnPc) derivatives, either asymmetrically or symmetrically substituted with 3 and 12 copies of the carbohydrate sialic acid (SA), respectively. Interestingly, the amphiphilic ZnPc-SA biohybrid ( 1 ) self-assembles into well-defined nanoaggregates in aqueous solution, facilitating cellular internalization and transport whereas the PS remains inactive. Within the cells, these nanostructured hybrids localize in the lysosomes, as usually happens for anionic and hydrophilic aggregated PS. Yet, in contrast to most of them (e. g., compound 2 ), hybrid 1 recovers the capacity for photoinduced ROS generation within the target organelles due to its amphiphilic character; this allows disruption of aggregation when the compound is inserted into the lysosomal membrane, with the concomitant highly efficient PDT response.     

Role of counteranions in polymeric ionic liquid-based solid-phase microextraction coatings for the selective extraction of polar compounds

A polymeric ionic liquid (PIL) poly(1-vinyl-3-hexylimidazolium chloride) (poly(ViHIm⁺Cl⁻)) was designed as a coating material for solid phase microextraction (SPME) to extract polar compounds including volatile fatty acids (VFAs) and alcohols. The extracted analytes were analyzed by using gas chromatography (GC) coupled with flame ionization detection (FID). Extraction parameters of the HS–SPME–GC–FID method, such as ionic strength, extraction temperature, pH and extraction time were optimized. Calibration studies were carried out under the optimized conditions to further evaluate the performance of the PIL-based SPME coating. For comparison purposes, the PIL poly(1-vinyl-3-hexylimidazolium bis[(trifluoromethyl)sulfonyl]imide) (poly(ViHIm⁺NTf₂⁻)) was also used as the SPME coating to extract the same analytes. The results showed that the poly(ViHIm⁺Cl⁻) PIL coating had higher selectivity towards more polar analytes due to the presence of the Cl⁻ anion which provides higher hydrogen bond basicity than the NTf₂⁻ anion. The limits of detection (LODs) determined by the designed poly(ViHIm⁺Cl⁻) PIL coating ranged from 0.02 μg L⁻¹ for octanoic acid and decanoic acid and 7.5 μg L⁻¹ for 2-nitrophenol, with precision values (as relative standard deviation) lower than 14%. The observed performance of the poly(ViHIm⁺Cl⁻) PIL coating was comparable to previously reported work in which commercial or novel materials were used as SPME coatings. The selectivity of the developed PIL coatings was also evaluated using heptane as the matrix solvent. This work demonstrates that the selectivity of PIL-based SPME coatings can be simply tuned by incorporating different counteranions to the sorbent coating.     

Adaptive Evolution of <Emphasis Type="Italic">Escherichia coli</Emphasis> Inactivated in the Phosphotransferase System Operon Improves Co-utilization of Xylose and Glucose Under Anaerobic Conditions

Modification of the phosphoenolpyruvate/sugar phosphotransferase system (PTS) has shown improvement in sugar coassimilation in Escherichia coli production strains. However, in preliminary experiments under anaerobic conditions, E. coli strains with an inactive PTS and carrying pLOI1594, which encodes pyruvate decarboxylase and alcohol dehydrogenase from Zymomonas mobilis, were unable to grow. These PTS⁻ strains were previously evolved under aerobic conditions to grow rapidly in glucose (PTS^- Glucose⁺ phenotype). Thus, in this work, applying a continuous culture strategy under anaerobic conditions, we generate a new set of evolved PTS⁻ Glucose⁺ mutants, VH30N1 to VH30N6. Contrary to aerobically evolved mutants, strains VH30N2 and VH30N4 carrying pLOI1594 grew in anaerobiosis; also, their growth capacity was restored in a 100%, showing specific growth rates (μ ~ 0.12 h⁻¹) similar to the PTS⁺ parental strain (μ = 0.11 h⁻¹). In cultures of VH30N2/pLOI1594 and VH30N4/pLOI1594 using a glucose–xylose mixture, xylose was totally consumed and consumption of sugars occurred in a simultaneous manner indicating that catabolic repression is alleviated in these strains. Also, the efficient sugar coassimilation by the evolved strains caused an increment in the ethanol yields.     

Structure and properties of clay nano‐biocomposites based on poly(lactic acid) plasticized with polyadipates

The use of nano‐biocomposites based on plasticized poly(lactic acid) (PLA) has been proposed as a way to improve the polymer ductility and to expand PLA applications window. Novative nano‐biocomposites were elaborated with PLA plasticized by polyadipates (15 wt%) with different molar masses (from 1500 to 2500 Da), with 2.1 wt% of an organo‐modified montmorillonite (O‐MMT). These materials showed enhanced ductility and barrier properties. The clay was swelled in liquid polyadipates prior to their blending with PLA to facilitate chains intercalation and nanofiller exfoliation during melt‐blending. In certain processing conditions, quite homogenous and exfoliated structures were obtained, as shown by X‐ray diffraction (XRD) and transmission electronic microscopy (TEM) results. Irrespective of the average molar mass of the polyadipate, the clay addition induced a reduction in around 25% in oxygen transmission rate (OTR) without an important detriment in tensile properties. Nano‐biocomposites prepared with higher molar masses polyadipates showed the highest thermal stability as well as the lowest OTR, resulting in very promising and novative materials for different applications such as soft packaging. Copyright © 2010 John Wiley & Sons, Ltd.     

Resin diterpenes from Austrocedrus chilensis

Seventeen diterpenes belonging to the labdane, abietane and isopimarane skeleton classes were isolated from the resin of the Chilean gymnosperm Austrocedrus chilensis and identified by spectroscopic and spectrometric methods. The diterpene 12-oxo-labda-8(17),13E-dien-19 oic acid is reported for the first time as a natural product and 14 diterpenes are reported for the first time for the species.