The relationship between self-organization and membrane effects of aqueous dispersion systems of the thyroliberin oligopeptide

The relationship between rearrangement of the dispersed phase inducing considerable changes in the pH and nonmonotonic concentration dependences of membrane effects in aqueous systems of the endogenous regulatory peptide, thyroliberin (thyrotropin-releasing hormone), in 10^–3–10^–16 mol/L concentration range was demonstrated for the first time. The membrane structure modification in the 10^–13–10^–16 mol/L range was found to be due to accumulation of nanoassociates, while the oppositely directed pronounced structural changes in the 10^–6–10^–12 mol/L range may be associated with the coexistence and rearrangement of dispersed phases of various nature (domains and associates) whose action on membrane lipid components is regulated in this concentration range by the correlated changes in the dispersed phase parameters and pH.     

Total reflection X-ray fluorescence determination of rare earth elements in mineral water

A method is proposed for determination of lanthanum, cerium, praseodymium, neodymium, and samarium in mineral water by means of total-reflection X-ray fluorescence analysis. In this work, the combined technique of preconcentration of rare earth ions is used. This technique consists of coprecipitation of metal hydroxides on the collector (iron (III) hydroxide) and dispersive liquid–liquid microextraction of their complexes with 1-(2-pyridylazo)-2-naphthol by chloroform in the presence of ethanol. The use of the developed hybrid approach allows simultaneous determination of the mentioned metals in mineral water in the range n(10^–2–10¹) μg/L. The results of analysis of Arkhyz and Rychal-Su mineral waters by the proposed extraction–X-ray fluorescent method are confirmed by the literature data, obtained by inductively coupled plasma mass spectrometry.     

Application of microemulsions for the extraction of <Emphasis Type="Italic">o</Emphasis>-phthalate esters from soil with subsequent separation of microemulsions,simultaneous preconcentration,and gas chromatographic analysis of target components

The possible application of microemulsions as extractants for the extraction of o-phthalate esters from soils with the subsequent breakdown of microemulsions, simultaneous preconcentration of dialkhylphthalates in the organic phase, and their following gas chromatographic analysis with mass-spectrometric detection is demonstrated. The preconcentration factor was 18. The method is characterized by low detection limits, good selectivity, and reproducibility.     

Electronic properties of achiral and chiral gold nanotubes

The band structure of ten single-walled gold nanotubes of different radius and chirality angle have been calculated by the linearized augmented cylindrical wave method. For all tubes, the Fermi level crosses the half-filled band; therefore, the tubes are characterized by a metallic electronic structure. The band structure of the nanotubes changes relatively weakly with a change in nanotube structure. The valence band width for all the tubes is 9.1 eV. The density of states at the Fermi level remains unaltered with a change in chirality angle and decreases by 30% with an increase in radius from 3 to 12 Å.     

Effect of 3<Emphasis Type="Italic">d</Emphasis>-metal dopants on the electronic properties of hexagonal titanium dioxide nanotubes

The electronic structure of hexagonal TiO₂ nanotubes doped with 3d transition metals from Sc to Zn was calculated by the linearized augmented cylindrical wave method. The calculated densities of states demonstrate that the substitution of Sc, V, Co, Cu, or Fe atoms for a part of Ti atoms leads to the decrease in the band gap width of the material from 4 to 2 eV. Such nanotubes are promising materials for creation of electrodes for electrochemical photolysis of water.     

Phase equilibria in the Cu<Subscript>2</Subscript>S–La<Subscript>2</Subscript>S<Subscript>3</Subscript>–EuS system

Phase equilibria in the isothermal (970 K) and polythermal LaCuS₂–EuS, Cu₂S–EuLaCuS₃, LaCuS₂–EuLa₂S₄, and EuLaCuS₃–EuLa₂S₄ sections of the Cu₂S–La₂S₃–EuS system have been studied. EuLaCuS₃ (annealing at 1170 K) is of orthorhombic system, space group Pnma, a = 8.1366(1) Å, b = 4.0586(1) Å, c = 15.9822(2) Å, is isostructural to Ba₂MnS₃, and incongruently melts by the reaction EuLaCuS_3cryst (0.50 EuS; 0.50 LaCuS₂) ? 0.22 EuS SS (0.89 EuS; 0.11 LaCuS₂) + 0.78 liq (0.39 EuS; 0.61 LaCuS₂); ΔН = 52 J/g. The Cu₂S–La₂S3–EuS system has been found to contain five major subordinate triangles. At 970 K, tie-lines lie between EuLaCuS₃ and the Cu₂S, EuS, LaCuS₂, and EuLa₂S₄ phases and between the LaCuS₂ phase and the γ-La₂S₃–EuLa2S4 solid solution. Eutectics are formed between LaCuS₂ and EuLaCuS₃ at 26.0 mol % of EuS and T = 1373 K and between EuLaCuS3 and EuLa₂S₄ at 29.0 mol % of EuLa₂S₄ and T = 1533 K.     

Copper(II), nickel(II), and zinc(II) complexes with <Emphasis Type="Italic">o</Emphasis>-tozylaminobenzaldehyde 4,6-dimethylpyrimidyl hydrazone

o-Tosylaminobenzaldehyde dimethylpyrimidyl hydrazone and its copper(II), nickel(II), and zinc(II) complexesare synthesized and studied. According to the X-ray diffraction data, the zinc(II) complex has the structure of a tetragonal pyramid with the N₃O donor ligand environment. According to EPR and magnetochemistry data, the copper(II) complex has a similar structure of the chelate core. In the nickel(II) complex, the solvent molecule completes the coordination core to an octahedron.     

Adsorption and catalytic properties of sulfated aluminum oxide modified with cobalt ions

The adsorption properties of sulfated aluminum oxide (9% SO ₄ ^2- /γ-Al₂O₃) and a cobalt-containing composite (0.5%Сo/SO ₄ ^2- /γ-Al₂O₃) based on it are studied via dynamic sorption. The adsorption isotherms of such test adsorbates as n-hydrocarbons (C₆–C₈), benzene, ethylbenzene, chloroform, and diethyl ether are measured, and their isosteric heats of adsorption are calculated. It is shown that the surface sulfation of aluminum oxide substantially improves its electron-accepting properties, and so the catalytic activity of SO ₄ ^2- /γ-Al₂O₃ in the liquid-phase alkylation of benzene with octene-1 at temperatures of 25–120°C is one order of magnitude higher than for the initial aluminum oxide. It is established that additional modification of sulfated aluminum oxide with cobalt ions increases the activity of this catalyst by 2–4 times. It is shown that adsorption sites capable of strong specific adsorption with both donating (aromatics, diethyl ether chemosorption) and accepting molecules (chloroform) form on the surface of sulfated γ-Al₂O₃ promoted by cobalt salt.     

Calculation of the formation enthalpies,standard entropies,and standard heat capacities of alkali and alkaline-earth germanates

The formation enthalpies, standard entropies, and standard heat capacities of alkali and alkaline-earth germanates were determined by regression analysis with allowance for error in the initial data (weights). The potentialities of the presented method of calculation appreciably grew due to the possibility to enhance the array of initial data independently of the crystal structure of compounds. The thermodynamic properties of alkali germanates were estimated for the first time and could be used in the physicochemical models of magmatic melts.     

Theoretical study of V<Subscript>20</Subscript>O<Subscript>50</Subscript> oxovanadate cluster compounds with alkali metal atoms

The energies and structural and spectroscopic characteristics of model М _n V₂₀O₅₀ systems corresponding to compounds of the V₂₀O₅₀ oxovanadate cluster with alkali metal atoms (M = Li, K; n = 1–20) have been calculated by the density functional theory method (B3LYP). It has been demonstrated that, in the K _n V₂₀O₅₀ compounds, all the metal atoms are coordinated in the outer sphere to the edges of the hollow dodecahedral V₂₀O₅₀ cage to form three-center O_t?K?O_t bridges with terminal oxygen atoms. In the Li _n V₂₀O₅₀ compounds, the metal atoms can be coordinated both outside and inside the V₂₀O₅₀ cage. At n = 4, the most favorable isomer is endohedral Li₄O₄@V₂₀O₄₆ in the quintet state (S = 5), in which the four Li atoms are located in the inner cavity of the inverted O₄@V₂₀O₄₆ isomer of the oxovanadate cluster with four O atoms oriented to the cage center and form with them a corrugated eight-membered ring Li₄O₄. The decrease in energy caused by the formation of the endohedral isomer (4Li + V₂₀O₄₅₀ → Li₄O₄@V₂₀O₄₆) is estimated at ~377 kcal/mol. The exohedral isomer 4Li ? V₂₀O₅₀ (S = 5), in which the Li atoms are coordinated to the outside of the V₂₀O₅₀ cage, is ~23 kcal/mol less favorable. For the other members of the Li series with n from 4 to 20, the endohedral isomers with the inner Li₄O₄ ring remain preferable. At n > 4, the extra Li atoms fill the outer sphere of the cage, being coordinated to its edges to form three-center O_t?Li?O_t bridges with terminal oxygen atoms. The specific energy of formation of Li _n V₂₀O₅₀ (by the scheme nLi + V₂₀O₄₅₀ → Li₄O₄@V₂₀O₄₆Li_n-4) per Li atom monotonically decrease from ~98 (n = 2) to ~80 kcal/mol (n = 20). For K _n V₂₀O₅₀, these energies are ~20?25 kcal/mol lower than for the lithium analogues and decrease from ~80 (n = 2) to ~64 kcal/mol (n = 12). The atoms of both alkali metals in the M _n V₂₀O₅₀ systems have large positive effective charges (0.85e?0.92e for K and 0.65e?0.78e for Li), which also monotonically decrease with increasing n. The addition of each alkali metal atom is accompanied by its ionization (М → М⁺) along with the reduction of one of the neighboring pentavalent vanadium atoms to the tetravalent state (V^V → V^IV) and localization of the unpaired electron in its 3d shell. For all Li _n V₂₀O₅₀ complexes, the states with maximal multiplicity and parallel spins are the most preferable.