New possibilities of X-ray nanocrystallography of biological macromolecules based on X-ray free-electron lasers

X-ray serial nanocrystallography is a new technique for determining the three-dimensional structure of biological macromolecules from data on the diffraction of ultrashort pulses generated by X-ray free-electron lasers. The maximum achievable resolution for a set of experimental data as a function of the sample sizes and parameters of the equipment is estimated based on simulations of the diffraction process with allowance for changes in the electronic structure of the atoms of the sample under the influence of X-rays. Estimates show that nanocrystallography greatly enhances the possibilities of X-ray analysis, reducing the requirements for the minimum permitted size of the crystals and enabling to explore poorly crystallizable molecular objects, such as many membrane proteins and complexes of macromolecules.     

Ozonocatalytic decomposition of glyoxal and glyoxylic and formic acids in the presence of iron(III) ions

Rate constants of reactions of ozone with glyoxal, glyoxylic and formic acid in aqueous solutions at pH 1.5 were determined. It was shown that iron(III) in the form of ions accelerates oxidation of glyoxal and glyoxylic acid, but does not influence reaction between ozone and formic acid. It was established that the catalyst acts effectively if its concentration is comparable to the concentration of the oxidized substrate, the optimal stoichiometric ratio (Fe³⁺/substrate) being close to 1/3. The catalytic reaction mechanism was studied using a competitive chelate ligand, oxalic acid. We concluded that the catalytic activity of iron(III) in the investigated reaction was due to its ability to form chelate complexes in which the substrate was more easily oxidized by molecular ozone.     

The kinetics of low-temperature oxidation of cobalt nanoparticles in porous media

The kinetics of oxidation of Co nanoparticles used in heterogeneous catalysis in silica gels and alumina with various porous structures was studied at room temperature. A mathematical model describing processes in the system was suggested. The experimental observations were qualitatively explained.     

Consistency of crystal-lattice parameters and thermalexpansion coefficients in five-component heterostructures based on compounds AIIIBV

The possibility of expansion of the limits of variation in the width of the forbidden band in five component solid solutions of compounds A^IIIB^V with consistency of crystallattice parameters and thermal-expansion parameters of the binary substrate and epitaxial layer is analyzed. Possible regions, and the corresponding character, of variation in composition in five-component solid solutions of compounds A_IIIB^V with simultaneous consistency of the crystal-lattice parameters and thermal-expansion coefficients with the binary substrates are identified.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 59–64, January, 1989.     

Oxidative dehydrogenation of propane on the VO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/CeZrO/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> supported catalyst

The oxidative dehydrogenation of propane on a supported vanadium catalyst was studied (the support was a complex oxide system consisting of a ceria–zirconia solid solution deposited on γ-Al₂O₃ (CeZrO/γ-Al₂O₃)). A comparative analysis of the properties of the support and the catalyst prepared on its basis was performed. The support and catalyst were characterized by the BET method, scanning electron microscopy, X-ray diffraction analysis, and Raman spectroscopy. The catalytic properties of the catalyst and support were studied in propane oxidation at 450 and 500°C with pulse feeding of the reagent. The effect of propane on the support was found to improve the oxidative properties of the latter. This behavior of the support is related to the preparation procedure, which leads to the formation on its surface of the crystalline phase of the ceria–zirconia solid solution and amorphous ZrO₂ and Al₂O₃ phases and/or their solid solution. Similar processes occur with the catalyst support during the oxidative dehydrogenation, giving rise to additional active centers (CeVO₄).     

Oxidizing of ferulic acid with the use of polyoxometalates as catalysts

The kinetics of catalytic oxidation for ferulic acid with polyoxometalates used as catalysts was studied. The effect of pH and concentrations of the principal reacting components on the process kinetics was studied. A kinetic scheme of oxidation is proposed, and the values of a number of kinetic parameters of the process are determined.     

The ozonization of model lignin compounds in aqueous solutions catalyzed by Mn(II) ions

The influence of Mn(II) ions on the rate of the reaction between ozone and model lignin compounds, guaiacol and veratrole, was studied. The catalyst did not influence the rate of the destruction of the aromatic ring and intermediate ozonolysis products, compounds with conjugated double bonds, in acid media but substantially increased the rate of oxidation of saturated carboxylic acids, ketoacids, and aldehydes. Ozone consumption then increased from 2 to 5 moles per mole of the transformed substrate. A mechanism of the catalytic action of Mn(II) in reactions between ozone and the compounds studied was suggested.     

Catalytic reactions of hydrocarbons promoted by coordination unsaturated Zr and Ti compounds: A density functional theory study

The paper is a review of a series of publications devoted to a number of homogeneous and heterogeneous catalytic reactions, their mechanisms, and energy characteristics. These reactions are promoted by coordination unsaturated compounds of Ti and Zr and proceed with cleavage and/or formation of C-C and C-H bonds in the hydrocarbon chain (polymerization reaction of ethylene, styrene, and butadiene-1,3, hydrogenolysis and hydroisomerization of linear and branched alkanes, and H/D isotope exchange in alkanes). A high-level quantum chemical method (DFT, PBE functional, gauss type TZ2p basis sets, the original PRIRODA program) was applied for the catalytic systems under the study. The nature and the structure of the active center, detailed mechanisms, and energy profile of the reaction of the substrate with a catalytic particle are considered. We compare our data with the results of both experimental and theoretical contributions from other authors.