Effect of Lithium Tetrafluoroborate on the Solubility of Carbon Dioxide in the Ionic Liquid 1-Butyl-3-Methylimidazolium Tetrafluoroborate

In this work, the phase behavior of the ternary system of carbon dioxide +1-butyl-3-methylimidazolium tetrafluoroborate?+?lithium tetrafluoroborate has been investigated. Mixtures of known concentrations of the salt, ionic liquid and carbon dioxide were prepared and their bubble point pressures were measured at different temperatures. Results are reported for this ternary system, at carbon dioxide concentrations of 20.2, 27.6 and 35.2?mol-% and salt concentrations of 0.0, 6.0, 11.5, 16.3 and 21.1?mol-% (on a carbon-dioxide free basis) and within temperature and pressure ranges of 293.15?C358.15?K and 1.2?C11.3?MPa, respectively. It was observed that the addition of the salt increased the bubble point pressure and its effect was concentration-dependent, i.e. at higher concentrations of the salt, higher pressures are required. This behavior is greater at higher temperatures.     

High-voltage power supplies to capillary and microchip electrophoresis

Over the past years, the development of capillary electrophoresis (CE) and microchip electrophoresis (ME) systems has grown due to instrumental simplicity and wide application. In both CE and ME, the application of a high voltage (HV) is a crucial step in the electrokinetic (EK) injection and separation processes. Particularly on ME devices, EK injection is often performed with three different modes: gated, pinched, and unpinched. In all these cases, different potential values may be applied to one or multiple channels to control the injection of small sample volumes as well as the separation process. For this reason, the construction of reliable HV power supplies (HVPS) is required. This review covers the advances of the development of commercial and laboratory-built HVPS for CE and ME. Moreover, it intends to be a guide for new developers of electrophoresis instrumentation.     

Theoretical study of disubstituted pyrrolopyrimidines as focal adhesion kinase inhibitors

An in silico molecular modeling study of selected 7H‐pyrrolo[2,3‐d]pyrimidines with FAK inhibitory activities was performed. Rigid docking of each inhibitor at the FAK catalytic site was employed to obtain the most appropriate starting structures, followed by molecular mechanics‐based energy minimizations associated with molecular dynamics at the FAK binding site using the AMBER force field. Theoretical values of interaction energies obtained from the geometry optimization calculations for the protein‐inhibitor complexes were compared with published IC₅₀ values for FAK and showed a reasonable correlation. Based on these results and in view of the geometry of the most potent inhibitors, two new molecular structures were designed as possible FAK inhibitors and submitted to the same theoretical procedures. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Molecular properties via a subsystem density functional theory formulation: a common framework for electronic embedding

In this article, we present a consistent derivation of a density functional theory (DFT) based embedding method which encompasses wave-function theory-in-DFT (WFT-in-DFT) and the DFT-based subsystem formulation of response theory (DFT-in-DFT) by Neugebauer [J. Neugebauer, J. Chem. Phys. 131, 084104 (2009)] as special cases. This formulation, which is based on the time-averaged quasi-energy formalism, makes use of the variation Lagrangian techniques to allow the use of non-variational (in particular: coupled cluster) wave-function-based methods. We show how, in the time-independent limit, we naturally obtain expressions for the ground-state DFT-in-DFT and WFT-in-DFT embedding via a local potential. We furthermore provide working equations for the special case in which coupled cluster theory is used to obtain the density and excitation energies of the active subsystem. A sample application is given to demonstrate the method.     

The rise of magnetochemistry from Ritter to Hurmuzescu

This paper describes the early history of magnetochemistry: the search for chemical effects of magnetism in the nineteenth century. Some early researchers, such as Johann Wilhelm Ritter, attempted to reproduce with magnets the effects that had been produced by electricity and Volta??s battery. For several decades, researchers successively reported positive results and denied claims concerning the effect of magnetism in oxidation, electrolysis, reduction of metals from saline solutions, crystallisation, change of colour of vegetable tinctures and other chemical reactions. In the two last decades of the nineteenth century some effects were accepted as real, and a thermodynamic theory of the influence of magnetic fields upon chemical reactions was developed. Finally, Dragomir Hurmuzescu was able to create reproducible experiments and measured the electromotive force between two electrodes, with or without the presence of magnetic fields, confirming the existence of the phenomenon and obtaining results compatible with the theoretical predictions. Afterwards, this magnetochemical effect was accepted as real, but the effect was weak and its practical importance was negligible. The subject was gradually forgotten.     

Electronic properties and dissociative photoionization of thiocyanates. Part II. Valence and shallow-core (sulfur and chlorine 2p) regions of chloromethyl thiocyanate, CH2ClSCN

A combination of photoelectron spectroscopy and synchrotron based photoelectron photoion coincidence (PEPICO) spectra has been applied to investigate the electronic structure and the dissociative ionization of the CH(2)ClSCN molecule in the valence region. The PES is assigned with the electronic structure calculations at the outer-valence Green's function and symmetry adapted cluster/configuration interaction (SAC-CI) levels offer an explanation of our experimental results. Upon vacuum ultraviolet irradiation the low-lying radical cation, located at 10.39 eV is formed. The molecular ion is observed in the time-of-flight mass spectra, together with the CH(2)SCN(+) and CH(2)Cl(+) daughter ions. The total ion yield spectra have been measured in the S 2p and Cl 2p regions and several channels have been determined in dissociative photoionization events for the core-excited species. Thus, by using time-of-flight mass spectrometry and synchrotron radiation the relative abundances of the ionic fragments and their kinetic energy release values were obtained from both PEPICO and photoelectron photoion photoion coincidence spectra. Possible fragmentation processes are discussed and compared with that found for the related CH(3)SCN species.     

Higher-order zincates as transmetalators in alkyl-alkyl negishi cross-coupling

Negishi revisited: higher-order alkyl zincates have been subjected to Negishi coupling with alkyl bromides. For the first time, coupling takes place in straight THF, i.e., without a salt additive and a high dielectric co-solvent. This provides evidence that it is the higher-order zincate that undergoes transmetalation to Pd, and not mono-anionic zincates or any of the other species present in the Schlenk equilibrium.     

Another side of the oxazaphospholidine oxide chiral ortho-directing group

A new ferrocenyl oxazaphospholidine oxide 3 was synthesized together with its P-epimer 2 in the reaction of ferrocene lithium with phosphoramidite chloride 1. 3 was successfully derivatized into planar chiral 1,2-ferrocenes, including phosphine ligands, via highly diastereoselective ortho-lithiation and subsequent functionalization; these compounds display opposite planar chirality to those obtained from 2. Some of these 1,2-ferrocenes were further lithiated, allowing for the introduction of a free phosphine group at the oxazaphospholidine ring. The X-ray structures of the compounds 2 and 3 as well as those of the new 1,2-ferrocenes 4 and 7 have been determined.     

Histidine affinity chromatography-based methodology for the simultaneous isolation of Escherichia coli small and ribosomal RNA

Research on RNA has led to many important biological discoveries and the improvement of therapeutic technologies. In particular, there is a great focus on small RNA and ribosomal RNA owing to their key functions in the cell, which make them excellent therapeutic targets. Although the study of these RNA classes is progressing, some limitations have been found regarding the use of suitable techniques that are able to produce and isolate biologically competent and chemically stable RNA. To address this, we have developed a novel histidine affinity chromatography-based isolation methodology for small and ribosomal RNA molecules. The new procedure involves three main steps: (1) cell lysis with guanidinium buffer, (2) RNA primary isolation with ammonium sulfate precipitation and (3) histidine affinity chromatography to specifically purify small RNA and ribosomal RNA from other Escherichia coli impurities (genomic DNA and proteins). The RNA quality assessment revealed that both RNA species were obtained with a high recovery, integrity and purity. The potential of this method to achieve a reproducible RNA isolation with appropriate quality has been demonstrated and it should have broad application in the structural, biophysical and biomedical investigation of systems involving RNA components.     

What is the flow activation volume of entangled polymer melts?

We evaluate the flow activation volume in polymer melts of isotactic polypropylene and atactic polystyrene with step-shear experiments at different melt temperatures. The melt is initially sheared with constant shear rate until the attainment of a melt state with nearly constant viscosity. Perturbations to this experiment, involving shear steps in short-time intervals with decreasing rates, are induced next. Measurements of the shear stress value at each shear rate step allow the evaluation of an experimental (apparent) flow activation volume. The true flow activation volume is evaluated by extrapolating the experimental data to infinite shear stress values. The value obtained is larger than the physical volume of the chain and agrees with the volume of a tube confining chains with a molecular weight between M _n and M _w. Besides supporting the validity of tube model, experiments based on this protocol may be used on model polymer samples, in composites with nanoparticles and in polymer blends to access the validity of mechanisms considered by flow models.