Simulation of flux during electro-membrane extraction based on the Nernst-Planck equation

The present work has for the first time described and verified a theoretical model of the analytical extraction process electro-membrane extraction (EME), where target analytes are extracted from an aqueous sample, through a thin layer of 2-nitrophenyl octylether immobilized as a supported liquid membrane (SLM) in the pores in the wall of a porous hollow fibre, and into an acceptor solution present inside the lumen of the hollow fibre by the application of an electrical potential difference. The mathematical model was based on the Nernst-Planck equation, and described the flux over the SLM. The model demonstrated that the magnitude of the electrical potential difference, the ion balance of the system, and the absolute temperature influenced the flux of analyte across the SLM. These conclusions were verified by experimental data with five basic drugs. The flux was strongly dependent of the potential difference over the SLM, and increased potential difference resulted in an increase in the flux. The ion balance, defined as the sum of ions in the donor solution divided by the sum of ions in the acceptor solution, was shown to influence the flux, and high ionic concentration in the acceptor solution relative to the sample solution was advantageous for high flux. Different temperatures also led to changes in the flux in the EME system.     

Upper and Lower Hausdorff Dimension Estimates for Invariant Sets of k — 1 — Endomorphisms

For a special class of non–injective maps on Riemannian manifolds upper and lower bounds for the Hausdorff dimension of invariant sets are given in terms of the singular values of the tangent map. The upper estimation is based on a theorem by Douady and Oesterlé and its generalization to Riemannian manifolds by Noack and Reitmann , but additionally information about the noninjectivity is used. The lower estimation can be reached by modifying a method, derived by Shereshevskij for geometric constructions on the real line (also described by Barreira , for similar constructions in general metric spaces. The upper and lower dimension estimates for k — 1 — endomorphisms can for instance be applied to Julia sets of quadratic maps on the complex plane.     

Low-Temperature Photochemistry of Previtamin D: A Hula-Twist Isomerization of a Triene

What is the standard course of the cis – trans isomerization of nonpolar polyenes? Many results support a pathway in which only a central CH group rotates out of the plane, while the remaining parts of the molecule reorient within the plane (“hula-twist” mechanism). The intermediate structure through which the molecule passes corresponds to the geometry predicted for the conical intersection of the S₁ and S₀ potential energy surfaces (see picture).     

Inhibition of Cytosolic Phospholipase A2α Induces Apoptosis in Multiple Myeloma Cells

Cytosolic phospholipase A2α (cPLA2α) is the rate-limiting enzyme in releasing arachidonic acid and biosynthesis of its derivative eicosanoids. Thus, the catalytic activity of cPLA2α plays an important role in cellular metabolism in healthy as well as cancer cells. There is mounting evidence suggesting that cPLA2α is an interesting target for cancer treatment; however, it is unclear which cancers are most relevant for further investigation. Here we report the relative expression of cPLA2α in a variety of cancers and cancer cell lines using publicly available datasets. The profiling of a panel of cancer cell lines representing different tissue origins suggests that hematological malignancies are particularly sensitive to the growth inhibitory effect of cPLA2α inhibition. Several hematological cancers and cancer cell lines overexpressed cPLA2α, including multiple myeloma. Multiple myeloma is an incurable hematological cancer of plasma cells in the bone marrow with an emerging requirement of therapeutic approaches. We show here that two cPLA2α inhibitors AVX420 and AVX002, significantly and dose-dependently reduced the viability of multiple myeloma cells and induced apoptosis in vitro. Our findings implicate cPLA2α activity in the survival of multiple myeloma cells and support further studies into cPLA2α as a potential target for treating hematological cancers, including multiple myeloma.     

The octet rule in chemical space: generating virtual molecules

We present a generator of virtual molecules that selects valid chemistry on the basis of the octet rule. Also, we introduce a mesomer group key that allows a fast detection of duplicates in the generated structures. Compared to existing approaches, our model is simpler and faster, generates new chemistry and avoids invalid chemistry. Its versatility is illustrated by the correct generation of molecules containing third-row elements and a surprisingly adept handling of complex boron chemistry. Without any empirical parameters, our model is designed to be valid also in unexplored regions of chemical space. One first unexpected finding is the high prevalence of dipolar structures among generated molecules.     

Synthesis,structure and properties of eight novel molybdenum(VI) complexes of the types: [MoO2LD] and [{MoO2L}2D] (L = thiosemicarbazonato ligand,D = N-donor molecule)

Eight new molybdenum(VI) complexes with 4-(diethylamino)salicylaldehyde and 2-hydroxy-3-methoxybenzaldehyde thiosemicarbazones have been prepared. They were characterized as mononuclear [MoO₂LD] or dinuclear [{MoO₂L}₂D] complexes. In all the compounds the MoO₂²⁺ core is coordinated by a tridentate ONS thiosemicarbazonato ligand and by the N-donor molecule (imidazole, pyridine or γ-picoline). All the complexes were characterized by chemical analysis, IR spectroscopy and thermogravimetry. Three of the mononuclear complexes, dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(pyridine)]molybdenum(VI), dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(γ-picoline)]molybdenum(VI) and dioxo[(2-hydroxy-3-methoxybenzaldehyde thiosemicarbazonato)(imidazole)]molybdenum(VI) were also characterized by single-crystal X-ray structural analysis. A spectrophotometric method for the determination of molybdenum based on extraction of ion-pairs formed by the cationic surfactant and the [MoO(SCN)₄]⁻ anion is described.     

Determination of uranium and thorium in complex samples using chromatographic separation, ICP-MS and spectrophotometric detection

The paper describes a research of possible application of UTEVA and TRU resins and anion exchanger AMBERLITE CG-400 in nitrate form for the isolation of uranium and thorium from natural samples. The results of determination of distribution coefficient have shown that uranium and thorium bind on TRU and UTEVA resins from the solutions of nitric and hydrochloric acids, and binding strength increases proportionally to increase the concentration of acids. Uranium and thorium bind rather strongly to TRU resin from the nitric acid in concentration ranging from 0.5 to 5 mol L⁻¹, while large quantities of other ions present in the sample do not influence on the binding strength. Due to the difference in binding strength in HCl and HNO₃ respectively, uranium and thorium can be easily separated from each other on the columns filled with TRU resin. Furthermore, thorium binds to anion exchanger in nitrate form from alcohol solutions of nitric acid very strongly, while uranium does not, so they can be easily separated. Based on these results, we have created the procedures of preconcentration and separation of uranium and thorium from the soil, drinking water and seawater samples by using TRU and UTEVA resins and strong base anion exchangers in nitrate form. In one of the procedures, uranium and thorium bind directly from the samples of drinking water and seawater on the column filled with TRU resin from 0.5 mol L⁻¹ HNO₃ in a water sample. After binding, thorium is separated from uranium with 0.5 mol L⁻¹ HCl, and uranium is eluted with deionised water. By applying the described procedure, it is possible to achieve the concentration factor of over 1000 for the column filled with 1 g of resin and splashed with 2 L of the sample. Spectrophotometric determination with Arsenazo III, with this concentration factor results in detection limits below 1 μg L⁻¹ for uranium and thorium. In the second procedure, uranium and thorium are isolated from the soil samples with TRU resin, while they are separated from each other on the column filled with anion exchanger in alcohol solutions. Anion exchanger combined with alcohol solutions enables isolation of thorium from soil samples and its separation from a wide range of elements, as well as spectrophotometric determination, ICP-MS determination, and other determination techniques.     

Using an electrical potential to reversibly switch surfaces between two states for dynamically controlling cell adhesion

Smart surfaces presenting both antifouling molecules with a charged functional group at their distal end, and molecules that are terminated by RGD peptides for cell adhesion, were fabricated and characterized (see picture). By applying potentials of +300 or -300?mV, the surfaces could be dynamically switched to make the peptide accessible or inaccessible to cells.     

The manganese ion of the heterodinuclear Mn/Fe cofactor in Chlamydia trachomatis ribonucleotide reductase R2c is located at metal position 1

The essential catalytic radical of Class-I ribonucleotide reductase is generated and delivered by protein R2, carrying a dinuclear metal cofactor. A new R2 subclass, R2c, prototyped by the Chlamydia trachomatis protein was recently discovered. This protein carries an oxygen-activating heterodinuclear Mn(II)/Fe(II) metal cofactor and generates a radical-equivalent Mn(IV)/Fe(III) oxidation state of the metal site, as opposed to the tyrosyl radical generated by other R2 subclasses. The metal arrangement of the heterodinuclear cofactor remains unknown. Is the metal positioning specific, and if so, where is which ion located? Here we use X-ray crystallography with anomalous scattering to show that the metal arrangement of this cofactor is specific with the manganese ion occupying metal position 1. This is the position proximal to the tyrosyl radical site in other R2 proteins and consistent with the assumption that the high-valent Mn(IV) species functions as a direct substitute for the tyrosyl radical.     

"Click"-modification of a functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) soluble in organic solvents

A PEDOT-based conductive copolymer soluble in organic solvents was synthesized electrochemically using dihexyl-EDOT and azidomethyl-EDOT as monomers and was successfully post-functionalized by "click"-cycloaddition reaction with a functionalized terminal alkyne under mild heterogeneous conditions.