Salts of poly(4-vinylpyridinium) with bis(2-ethylhexyl) sulfosuccinate: Coils and globules of the single molecules observed by dynamic light scattering,stabilization of the reversed emulsions

Poly(4-vinylpyridine) derivatives alkylated with dimethylsulfate, octylbromide and dodecylbromide were synthesized. Counter ions in the polymer salts were substituted with bis(2-ethylhexyl)sulfosuccinate. The solutions of the polyelectrolyte-surfactant complexes in the mixtures of decane with chloroform were studied by dynamic light scattering. At high decane content all the complexes have expanded coil conformations. The increase of chloroform content over 60 vol.% leads to folding of the coils to globule state and to the appearance of the second peak on the DLS curves corresponding to the small fraction of large particles with hydrodynamic radii R ca 40–80 nm. The ability of the synthesized complexes to stabilize reversed emulsions was studied. It was shown that polymer complexes of AOT with comb-like polycations stabilize emulsions of water in 4:1 mixture of decane with chloroform. Addition of sodium chloride to the system markedly increases stabilizing effect of the comb-like polycations with AOT.     

Activating Effect of 3-Benzylidene Oxindoles on AMPK: From Computer Simulation to High-Content Screening

AMP-activated protein kinase (AMPK) is currently the subject of intensive study and active discussions. AMPK performs its functions both at the cellular level, providing the switch between energy-consuming and energy-producing processes, and at the whole body level, particularly, regulating certain aspects of higher nervous activity and behavior. Control of such a ‘main switch’ compensates dysfunctions and associated diseases. In the present paper, we studied the binding of 3-benzylidene oxindoles to the kinase domain of the AMPK α-subunit, which is thought to prevent its interaction with the autoinhibitory domain and thus result in the AMPK activation. For this purpose, we developed the cellular test system based on the AMPKAR plasmid, which implements the FRET effect, synthesized a number of 3-benzylidene oxindole compounds and simulated their binding to various sites of the kinase domain. The most probable binding site for the studied compounds was established by the correlation of calculated and experimental data. The obtained results allow to analyze various classes of AMPK activators using virtual and high-content screening.     

Photocatalytic hydrogen evolution from aqueous solutions of glycerol under visible light irradiation

Multiphase photocatalysts Pt/Cd_1−xZn_xS/ZnO/Zn(OH)₂ and single-phase photocatalysts Pt/Cd_1−xZn_xS were prepared by a two-step technique. The photocatalysts were characterized by a wide range of experimental techniques: X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray (EDX) spectroscopy, low-temperature N₂ adsorption/desorption, and UV/VIS spectroscopy. The photocatalytic activity was tested in a batch reactor in the reaction of hydrogen evolution from aqueous solutions of glycerol under visible light irradiation (λ > 420 nm). The highest achieved photocatalytic activity was 449 μmol H₂ per gram of photocatalyst per hour; the highest quantum efficiency was 9.6% (λ > 420 nm). The activity of the multiphase catalysts was shown to exceed that of the single-phase catalysts by a factor of 2.1, likely because of the heterojunctions between sulfides, oxides and hydroxides.     

New tolerant strains of purple nonsulfur bacteria for hydrogen production in a two-stage integrated system

In this study we described the isolation of eight new strains of purple non-sulfur bacteria resistant to salinity ≥30 g L⁻¹ and high concentration of VFAs (200 mM). These strains were characterized by their general physiological properties and the occurrence of hupSL genes. Some correlation was observed between the rate of H₂ photoproduction, the absence of hupSL genes and hydrogenase activity. Two fast-growing strains without hupSL genes showed high nitrogenase activity and hydrogen accumulation during growth on Ormerod medium. These strains were capable of H₂ photoproduction using non-treated dark culture (75% in water) after dark fermentation of starch at 30 g L⁻¹, unlike control strains, Rhodobacter capsulatus B10 and Rb. sphaeroides GL. New N7 and 13 strains identified as Rb. sphaeroides can be recommended for application in a two-stage H₂ production system.     

Structure of atmospheric-pressure fuel-rich premixed ethylene flame with and without ethanol

Effect of ethanol (EtOH) addition to unburnt gas mixture on the species pool in a fuel-rich flat, premixed, laminar ethylene flame at atmospheric pressure is studied experimentally and by chemical kinetic modeling. Mole fraction profiles as a function of height above burner of various stable and labile species including reactants, major products and intermediates (C₁–C₄ hydrocarbons) are measured using molecular beam mass spectrometry with electron ionization in C₂H₄/O₂/Ar and C₂H₄/EtOH/O₂/Ar flames. The experimental profiles are compared with those calculated using three different chemical kinetic mechanisms. Performances and deficiencies of the mechanisms are discussed. An analysis of the mechanisms is carried out in order to identify the reason of the ethanol effect on the mole fraction of propargyl, the main precursor of benzene. A modification of some mechanisms in order to improve their capability to predict acetylene and diacetylene mole fraction profiles is proposed.     

Electrophilic Fluorination of Aromatics with Selectfluor™ and Trifluoromethanesulfonic Acid1

1-(chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane bis (tetrafluoroborate) [Selectfluor™ F-TEDA-BF₄ (TEDA = triethylenediamine)] in the presence of trifluoromethanesulfonic acid has been found to be a very effective reagent system for the direct electrophilic fluorination of a wide variety of aromatic compounds under mild reaction conditions to the corresponding fluoroaromatics in good to excellent yields.     

Catalysts for sanitary air cleaning from ozone

The results of the kinetic study of ozone decomposition over carbon fibrous materials and metal complex compounds (CuCl₂) supported on them at ozone concentrations in the 3.1 × 10^–8–3.1 × 10^–5 mol/l range are presented. Ozone decomposition occurs mainly in a catalytic way with the steady-state regime attainment depending on CFM physico-chemical as well as structural characteristics and macrokinetic factors of the process. Copper (II) catalyzes decomposition of ozone microconcentrations only. The data obtained can be a base for the development of sanitary air cleaning units and respirators (protective gas-masks).     

Comb-like poly(4-vilylpyridinium) salts with dodecylsulfate, sodium bis(2-ethylhexyl) sulfosuccinate and bromide counter ions. Small-angle X-ray scattering and dynamic light scattering study

Poly(4-vinylpyridine) derivatives alkylated with dimethylsulfate, octylbromide and dodecylbromide were synthesized. Bromide anions in the polymer salts were substituted with octylsulfate, dodecylsulfate or bis(2-ethylhexyl)sulfosuccinate (AOT) anions using ion-exchange reactions. The small-angle X-ray scattering (SAXS) studies of the structure of the comb-like polysalts demonstrated their highly-ordered structure. Loading the comb-like polycation with the surfactant anions leads to additional ordering of the polysalts structure. In the case of large AOT anions the transition from lamella to hexagonal structure is observed. Polyelectrolyte - surfactant complexes (PEC) of poly(4-vinyl-1-methylpyridinium) cation with octylsulfate and dodecylsulfate counter ions demonstrate a higher degree of order than the comb-like polymers having a similar chemical structure. The SAXS studies were complemented by dynamic light scattering study of the solutions of the polymers in chloroform. In the solution the comb-like polymers and their complexes with linear surfactants have coil conformations with the size of the coils close to that of the original poly-4-vinylpyridine. The conformations of PECs with octylsulfate and dodecylsulfate counter ions are more unfolded than those of the corresponding comb-like polymers.     

Preparation of Hard Alloy WC and WC – Co Mixtures with Reduction and Carbidizing Treatment of Oxidized Tungsten Containing Scrap

A method of single-stage reduction and carbidizing treatment of oxidized tungsten containing scrap (hard alloys of the VK type and tungsten wire) is proposed. Procedures are suggested for preparing very fine tungsten carbide of stoichiometric composition without adding carbon black by reduction and carbidizing treatment of oxidized tungsten wire scrap and also with introduction of solid carbon (carbon black) during reduction and carbidizing treatment of oxidized hard alloy scrap.