On the significance of the anchoring group in the design of antenna materials based on phthalocyanine stopcocks and zeolite L

The synthesis of stopcocks based on zinc phthalocyanine for selective adsorption at the channel entrances of zeolite L is reported. The introduction of either an inert SiMe? moiety, an imidazolium cation or a reactive isothiocyanate (NCS) group allows attachment to the channel entrances of zeolite L through van der Waals interactions, electrostatic interactions, or covalent binding, respectively. Stopcocks that rely on van-der-Waals-driven adsorption require careful selection of the solvent used for the deposition onto the zeolite surface to avoid a nonspecific distribution of the molecules. Regarding the design of photonic antenna systems, a stopcock with a cationic tail was found to be the most convenient, based on the observation that efficient energy transfer from molecules located in the zeolite nanochannels is more readily obtained than in the other cases.     

Highly stable cooperative distortion in a weak Jahn-Teller d2 cation: perovskite-type ScVO3 obtained by high-pressure and high-temperature transformation from bixbyite

A novel ScVO(3) perovskite phase has been synthesized at 8 GPa and 1073 K from the cation-disordered bixbyite-type ScVO(3). The new perovskite has orthorhombic symmetry at room temperature, space group Pnma, and lattice parameters a = 5.4006(2) ?, b = 7.5011(2) ?, and c = 5.0706(1) ? with Sc(3+) and V(3+) ions fully ordered on the A and B sites of the perovskite cell. The vanadium oxygen octahedra [V-O(6)] display cooperative Jahn-Teller (JT) type distortions, with predominance of the tetragonal Q(3) over the orthorhombic Q(2) JT modes. The orthorhombic perovskite shows Arrhenius-type electrical conductivity and undergoes a transition to triclinic symmetry space group P-1 close to 90 K. Below 60 K, the magnetic moments of the 4 nonequivalent vanadium ions undergo magnetic long-range ordering, resulting in a magnetic superstructure of the perovskite cell with propagation vector (0.5, 0, 0.5). The magnetic moments are confined to the xz plane and establish a close to zigzag antiferromagnetic mode.     

Study of the capillary electrophoresis profile of intact α-1-acid glycoprotein isoforms as a biomarker of atherothrombosis

α-1-Acid glycoprotein (AGP) is a serum glycoprotein that presents several isoforms. Changes in the isoforms of AGP have been related to different pathological states including cardiovascular diseases (CVDs) such as acute myocardial infarction. However, to our knowledge, the role of variations of AGP isoforms as a potential biomarker of atherothrombosis has not been addressed. In this work, a preliminary study about differences in the capillary zone electrophoresis (CZE) profile of intact (non-hydrolyzed) AGP isoforms between healthy individuals and patients with atherothrombosis, specifically abdominal aortic aneurysm (AAA) and carotid atherosclerosis (CTA), has been performed. Biological samples (plasmas and sera) were analyzed by CZE after immunoaffinity chromatography purification. Up to 13 peaks corresponding to groups of isoforms of intact AGP from plasma samples were detected by CZE-UV. Electrophoretic profiles were aligned, peaks assigned, and linear discriminant analysis (LDA) of percentage of the corrected areas of AGP peaks was employed to discriminate and classify the CZE profiles of AGP samples. LDA enabled to accomplish 92.9% of correct classification of the AGP samples when the three groups of samples were considered. Besides, the LDA model showed high predictive power in the groups healthy vs. sick, healthy vs. AAA, and healthy vs. CTA. The described method was a successful approach to study the potential of AGP isoforms profile as a biomarker of atherothrombosis. To the best of our knowledge this has been the first time that a possible role of the CZE profile of intact AGP isoforms as a biomarker of vascular diseases has been demonstrated.     

A simplified Quick, Easy, Cheap, Effective, Rugged and Safe approach for the determination of trihalomethanes and benzene, toluene, ethylbenzene and xylenes in soil matrices by fast gas chromatography with mass spectrometry detection

A method based on simplified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction followed by large-injection volume-fast gas chromatography and mass spectrometry detection has been developed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane and bromoform) and BTEX (benzene, toluene, ethylbenzene and xylenes) in soil samples.The simplified version of QuEChERS used meets the requirements of the “green chemistry” and provides reliable results with high sample throughput, low solvent consumption, little labour and the use of materials commonly employed in laboratories. The GC device used is equipped with a programmable temperature vaporizer (PTV), with a liner packed with Tenax-TA^®. Using the solvent-vent mode, the PTV allows the injection of large volumes of sample, affording an improvement in the sensitivity of the method. The chromatographic conditions used here allowed the separation of the compounds in less than 5.50 min. Good linearity was obtained for all the target compounds, with highly satisfactory repeatability and reproducibility values. The limits of detection were in the 0.2 to 15 μg kg⁻¹ range. The method was validated by the analysis of two certified reference materials.     

Comprehensive analysis of polycyclic aromatic hydrocarbons in wastewater using stir bar sorptive extraction and gas chromatography coupled to tandem mass spectrometry

The objective of this study was the optimization and comparison of two extraction methods for the determination of polycyclic aromatic hydrocarbons (PAHs) in wastewater (WW). A distribution study of the target compounds between the aqueous phase and the suspended particulate matter (SPM) has been performed in order to establish whether the analysis of both phases is necessary. In this sense, the feasibility of stir bar sorptive extraction (SBSE) and solid-phase extraction (SPE) for the determination of 24 PAHs in WW samples has been evaluated. The results demonstrated the suitability of SBSE to perform a comprehensive analysis of liquid samples containing high amounts of SPM, such as in the determination of PAHs in WWs. A gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) method has been also optimized for the separation and detection of the target compounds, avoiding the co-elution of some groups of isomers, such as benzo[b], [j] and [k] fluoranthenes and indene[1,2,3-cd]pyrene/dibenz[a,h]anthracene. For that purpose, a specific capillary column developed for PAH determination was used. The SBSE procedure was validated and adequate parameters (such as recovery, linearity, precision, limits of detection and quantification) were obtained. Finally, the validated method was applied to the analysis of real samples collected from an experimental WW treatment plant, detecting some PAHs at concentrations in the range 0.007-0.022 μg L(-1).     

Influence of quantum effects on the physisorption of molecular hydrogen in model carbon foams

The physisorption of molecular hydrogen in model carbon foams has been investigated from 50 K to room temperature. The study is carried out within the framework of the density functional theory for quantum liquids at finite temperatures. Calculations are performed in the grand canonical ensemble, i.e., the adsorbed fluid is assumed to be in equilibrium with an external gas of hydrogen molecules with concentrations ranging from 8×10(-4) kg m(-3) to n=71 kg m(-3). It is shown that, while strong zero-point energy effects are present even at room temperature, the adsorption isotherms exhibit only a weak dependence on the explicit incorporation of the bosonic exchange symmetry of hydrogen molecules. The increase of the average particle density prevents the deviations from the Maxwell-Boltzmann statistics to become noticeable if the system is cooled down. The volumetric storage capacity of these materials at low temperatures is about one half of the U. S. Department of Energy goal, while the gravimetric capacity is still far from the standards required by mobile applications. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed.     

Excited electron-bubble states in superfluid 4He: a time-dependent density functional approach

We present a systematic study on the excited electron-bubble states in superfluid (4)He using a time-dependent density functional approach. For the evolution of the 1P bubble state, two different functionals accompanied with two different time-development schemes are used, namely an accurate finite-range functional for helium with an adiabatic approximation for electron versus an efficient zero-range functional for helium with a real-time evolution for electron. We make a detailed comparison between the quantitative results obtained from the two methods, which allow us to employ with confidence the optimal method for suitable problems. Based on this knowledge, we use the finite-range functional to calculate the time-resolved absorption spectrum of the 1P bubble, which in principle can be experimentally determined, and we use the zero-range functional to real-time evolve the 2P bubble for several hundreds of picoseconds, which is theoretically interesting due to the break down of adiabaticity for this state. Our results discard the physical realization of relaxed, metastable configurations above the 1P state.     

Study on the conformational equilibrium of the alanine dipeptide in water solution by using the averaged solvent electrostatic potential from molecular dynamics methodology

The ASEP/MD method has been employed for studying the solvent effect on the conformational equilibrium of the alanine dipeptide in water solution. MP2 and density functional theory (DFT) levels of theory were used and results were compared. While in gas phase cyclic structures showing intramolecular hydrogen bonds were found to be the most stable, the stability order is reversed in water solution. Intermolecular interaction with the solvent causes the predominance of extended structures as the stabilizing contacts dipeptide-water are favoured. Free-energy differences in solution were calculated and PPII, α(R), and C5 conformers were identified as the most stable at MP2 level. Experimental data from Raman and IR techniques show discrepancies about the relative abundance of α(R) y C5, our results support the Raman data. The DFT level of theory agrees with MP2 in the location and stability of PPII and α(R) forms but fails in the location of C5. MP2 results suggest the possibility of finding traces of C7eq conformer in water solution, in agreement with recent experiments.     

Studies on the adsorption of cell impurities from plasmid-containing lysates to phenyl boronic acid chromatographic beads

Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins.