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Abstract: We have studied the concentration of vitamins A (retinol) and E (α-tocopherol) in the tissues of the bank vole (Myodes(Clethrionomys) glareolus) and common shrew (Sorex araneus) inhabiting the northern periphery of its natural habitat. The distribution of vitamin A in the common shrew and bank vole tissues is similar: the highest concentration is found in the liver, and the lowest level is found in the heart. Age-related differences in the retinol concentration are detected in the kidneys of the two species, as well as in the skeletal muscle of the shrew. A significantly lower vitamin E concentration is found in all organs of young shrews before wintering, compared to adult overwintered animals, while in the bank vole no such age-related differences are found. Interspecies differences in the levels of vitamins A and E in the liver of overwintered animals are revealed. The results obtained show that the concentration of vitamins A and E in the tissues of the bank vole and the common shrew is determined by metabolic processes and the ecological characteristics of the species. The level of vitamins in the common shrew depends largely on age.

Abstract—: The paper presents the results of structural studies of model niello compositions reproducing historical niello inlays on encolpion crosses from the Suzdal Opolye. The specifics of the formation of inlay phases at different stages of its melting are analyzed. Comparison of the modeling results and historical niello shows that the microstructural features of archaeological samples correspond to niello production by melting.

Seven polynorbornene samples containing trimethylsilyl side groups that were prepared by the addition polymerization of 5-trimethylsilyl-2-norbornene in the presence of catalytic systems (π-C5H9NiCl)2-methylaluminoxane and nickel naphthenate-methylaluminoxane have been studied by translational isothermal diffusion and viscometry. The molecular masses of the polymer samples are measured. Kuhn-Mark-Houwink equations for diffusion coefficient Dand intrinsic viscosity [η] are determined in toluene at 25°C: D= 6.94 × 10−4M−0.61and [η] = 1.53 × 10−3M0.82. The equilibrium rigidity of polymers chains is estimated as A= 47 ± 9 Å. The conformational features of the silicon-containing polynorbornene are analyzed by the PM3 quantumchemical semiempirical method on the basis of simulation of its decamer chain fragments. In terms of microstructure and equilibrium rigidity, the above-described addition poly(trimethylsilylnorbornene) is close to poly(trimethylsilylpropyne) synthesized using niobium pentachloride as a catalyst. This finding explains similar membrane gas-separation properties of these polymers.

Abstract: The molecular mass and hydrodynamic dimensions of molecules of two fullerene-containing polymers which differ in the preparation procedure and the mode of fullerene C60 binding were determined by means of static and dynamic light scattering and transport techniques (diffusion, sedimentation, gel permeation chromatography). It was established that the molecular masses of polymeric C60 derivatives determined by means of static light scattering are substantially above those measured by means of the transport techniques. Using as an example a polystyrene specimen containing 6.2 wt % C60 prepared according to the widespread technique of solvent evaporation from a mutual fullerene and polymer solution, it was shown that the multicomponent nature, the compositional inhomogeneity, and a lack of coincidence in the signs of refractive index increments for structurally different components of fullerene-containing polymers may cause anomalies in the intensity of light scattering by solutions of these compounds.

Abstract: The molecular properties and composition of fullerene-containing polystyrenes prepared through evaporation of solvent from the combined solution of a polymer and C60 in benzene have been studied by viscometry, translational isothermal diffusion, GPC, UV spectroscopy, and electrooptical Kerr effect measurements. With this procedure of C60 introduction into the polymer, a partial depolymerization of the parent polystyrene takes place. It has been shown that the composites contain fullerene in two forms: a smaller part of C60 is bound to macromolecules, while a larger part of C60 is incorporated into the composition of low-molecularmass adducts—the products arising from the interaction of fullerene with fullerene-induced depolymerized polystyrene.

Abstract: Comparative analysis of the methods for determination of the intrinsic viscosity of both neutral and polyelectrolyte molecules is made.

Abstract: Samples of sodium polystyrenesulfonate of molecular weights varying in a 20-fold range were synthesized. The hydrodynamic behavior of the samples was studied in a 0.2 M NaCl solution in which the initial polyelectrolyte effects are suppressed. Relationships between the molecular weight and the translational friction coefficient and intrinsic viscosity were obtained. The theory describing the hydrodynamic behavior of wormlike chains with taking into account both the percolation effects and the excluded-volume effects was applied to estimation of the length of the statistical segment and the cross section of the sodium polystyrenesulfonate molecules in 0.2 M NaCl solution.

Abstract Star-like water-soluble macromolecules with fullerene as the branching site were synthesized by the reaction of fullerene C60 with polyvinylpyrrolidone whose molecules contain one terminal primary amino group. The initial and C60-containing polymers were studied by UV spectroscopy, thin-layer chromatography, centrifugal sedimentation, translation diffusion, and viscometry in aqueous buffer solutions. Diffusion-sedimentation and sedimentation two-detector analyses of the initial and fullerene-containing samples were performed. The molecular weights of the polymers were estimated by the Svedberg equation. The proportion of the fullerene-containing segment in the samples synthesized was determined, and the number of the branches in the fullerene-containing macromolecules was estimated.

The birefringence of thin films of poly(1-trimethylsilylpropyne) with 55 : 45 ratio of units with transand cisconfigurations of the -C = C- bonds was studied by the method of an oblique polarized beam. The surface birefringence coefficients were determined for films of various thicknesses. A theory of birefringence in the surface layers of polymer films was suggested, based on the assumed exponential decrease in the orientation order parameters of the molecular chain fragments with increasing distance from the film surface.

Electron–diffraction and mass–spectrometric studies of saturated vapor of scandium tris–dipivaloyl–methanate showed that at 135(5)°, the vapor contains only monomeric Sc(thd)3, whose structural parameters ra, rg, and rαwere determined. The internuclear distances in the chelate ring were found to be rαSc=O) = 2.066(5)Å, rα(O=C) = 1.272(3)Å, and rα(C=Cr) = 1.385(3)Å. The ScO6coordination polyhedron has a D3symmetry configuration close to a regular antiprism. The angle of rotation of the O=O=O trigonal faces relative to their position in a regular prism is 25.7(1.5)°.

The methods of the Kerr effect and solution hydrodynamics were applied to study the electrooptical and hydrodynamic properties of samples of disubstituted polyacetylenes, poly(1-trimethylsilyl-1-propynes), prepared by polymerization of 1-trimethylsilyl-1-propyne with NbCl5and TaCl5/BuLi as catalysts. The experimental electrooptical characteristics of polymers were compared with those calculated by PM3 semiempirical quantum-chemical method.

The stability constants of 1 : 1 complexes of ammonium ion with 18-crown-6 in water and aqueous dioxane (dioxane weight fraction 0.2, 0.4, 0.6, and 0.8) in the range 283-318 K were determined electrometrically, and the thermodynamic parameters of the complexation were calculated. The stability of the complexes is determined by the enthalpy factor. The contributions from the Gibbs energy of solvation of NH4+ion, 18-crown-6·NH4+complex, and free 18-crown-6 to stabilization of the complex with increasing content of dioxane in the mixed solvent were estimated. The thermodynamics of complexation of ammonium, sodium, and potassium ions with 18-crown-6 in aqueous-organic solvents, such as water-2-propanol, water-acetone, and water-dioxane, were compared considering the effects of reactant solvation. The variations of the conformational component of the Gibbs energy of solvation of 18-crown-6 and the parameters of selective solvation of the reactants were evaluated. The influence of the dielectric permittivity and donor-acceptor properties of mixed aqueous-organic solvents on the Gibbs energy of complexation and solvation of the cations and 18-crown-6 was subjected to correlation analysis.

Synchronous electron diffraction and mass spectrometric investigation of the saturated vapor of scandium tris-acetylacetonate was carried out. It was stated that at 155(5)°C the vapor contains only monomeric Sc(aa)3molecules, whose structural parameters ra, rg, and rαwere determined. The internuclear distances in the chelate ring were found to be rα(Sc–O) = 2.076(4) Å, rα(O–C) = 1.271(3) Å, rα(C–Cr) = 1.386(4) Å. The coordination polyhedron ScO6has a nearly antiprism structure of D3symmetry. The angle of rotation of the O–O–O trigonal faces relative to their position in a regular prism is 26.8(1.1)°.

The preparative chemical method, X-ray diffraction analysis, and vacuum sublimation method are used to show that the mechanical treatment of mixtures of calcium chloride with sodium salts of acetylacetone, trifluoroacetylacetone, dipivaloylmethane, or acetylacetoimine induces their interaction, forming volatile calcium β-diketonates and sodium chloride. Heating of the reaction mixtures results in sublimation of the obtained calcium β-diketonate and nonreacted sodium β-diketonate; this is impeded by the formation of poorly volatile forms.

The structure and the relative stability of the N-, Cα-, and Cβ-anions of pyrrole, its mono- and dimethyl derivatives, and their adducts with carbon disulfide were studied by the ab initiomethod (MP2/6-31+G*//RHF/6-31+G*). The substituent effect on the reaction path is considered. For unsubstituted pyrrole, the stability of the adducts decreases in the series Cα> N > Cβ. The stability of the N-adducts decreases considerably in the presence of the methyl groups introduced into the α-position in view of steric interactions. Possible reasons for the experimentally observed formation of the thermodynamically less stable N-adduct of the unsubstituted pyrrole and for the absence of N-adducts in reactions of the methyl derivatives with CS2are discussed.

Stability constants of Na+complexes with 18-crown-6-ether and thermodynamic characteristics of the complex formation in water and mixed water-dioxane solvents (0.2, 0.4, 0.6, and 0.8 wt. fraction of dioxane, 283-318 K) were determined by the method of EMF of galvanic circuits without transfer. Comparative thermodynamic analysis of the complex 18-crown-6Na+formation reactions in water-dioxane, water-acetonitrile, water-acetone, water-methanol, and water-2-propanol mixtures was carried out. Contributions of the Gibbs energies of transfer (ΔGt) of 18-crown-6Na+, Na+, and the ligand to the increase in the stability of the complexes on replacement of water by mixed water-dioxane solvents were estimated. It was shown that the increase in the stability of sodium crown ether complexes primarily depends on solvation of the complex cation and desolvation of the central cation. Changes in the conformational Gibbs energy of the ligand and quantitative parameters of selective solvation of the reagents were estimated.

Abstract:  Ceruloplasmin is a multi-copper oxidase, which contains most of the copper present in the plasma. It is an acute-phase reactant that exhibits a two- to three-fold increase over the normal concentration of 300 μg/ml in adult plasma. However, the precise physiological role(s) of ceruloplasmin has been the subject of intensive debate and it is likely that the enzyme has a multi-functional role, including iron oxidase activity and the oxidation of biogenic amines. The three-dimensional X-ray structure of the human enzyme was elucidated in 1996 and showed that the molecule was composed of six cupredoxin-type domains arranged in a triangular array. There are six integral copper atoms per molecule (mononuclear sites in domains 2, 4 and 6 and a trinuclear site between domains 1 and 6) and two labile sites with roughly 50% occupancy. Further structural studies on the binding of metal cations by the enzyme indicated a putative mechanism for ferroxidase activity. In this paper we report medium-resolution X-ray studies (3.0–3.5 Å) which locate the binding sites for an inhibitor (azide) and various substrates [aromatic diamines, biogenic amines and (+)-lysergic acid diethylamide, LSD]. The binding site of the azide moiety is topologically equivalent to one of the sites reported for ascorbate oxidase. However, there are two distinct binding sites for amine substrates: aromatic diamines bind on the bottom of domain 4 remote from the mononuclear copper site, whereas the biogenic amine series typified by serotonin, epinephrine and dopa bind in close vicinity to that utilised by cations in domain 6 and close to the mononuclear copper. These binding sites are discussed in terms of possible oxidative mechanisms. The binding site for LSD is also reported.

Staphylococcal enterotoxins are prototype superantigens characterized by their ability to bind to major histocompatibility complex (MHC) class II molecules and subsequently activate a large fraction of T‐lymphocytes. The crystal structure of staphylococcal enterotoxin type A (SEA), a 27 kDa monomeric protein, was determined to 1.9 A resolution with an R‐factor of 19.9% by multiple isomorphous replacement. SEA is a two domain protein composed of a beta‐barrel and a beta‐grasp motif demonstrating the same general structure as staphylococcal enterotoxins SEB and TSST‐1. Unique for SEA, however, is a Zn2+ coordination site involved in MHC class II binding. Four amino acids including Ser1, His187, His225 and Asp227 were found to be involved in direct coordination of the metal ion. SEA is the first Zn2+ binding enterotoxin that has been structurally determined.

Staphylococcal enterotoxins are prototype superantigens characterized by their ability to bind to major histocompatibility complex (MHC) class II molecules and subsequently activate a large fraction of T‐lymphocytes. The crystal structure of staphylococcal enterotoxin type A (SEA), a 27 kDa monomeric protein, was determined to 1.9 A resolution with an R‐factor of 19.9% by multiple isomorphous replacement. SEA is a two domain protein composed of a beta‐barrel and a beta‐grasp motif demonstrating the same general structure as staphylococcal enterotoxins SEB and TSST‐1. Unique for SEA, however, is a Zn2+ coordination site involved in MHC class II binding. Four amino acids including Ser1, His187, His225 and Asp227 were found to be involved in direct coordination of the metal ion. SEA is the first Zn2+ binding enterotoxin that has been structurally determined.

Crystal structures for both native and recombinant forms of yeast fumarase from Saccharomyces cerevisiaehave been completed to moderate resolution by two separate laboratories. The recombinant form was obtained by the construction of an expression plasmid for Escherichia coli. Despite a high level of amino acid sequence similarity, purification of the eukaryotic enzyme from the wild-type prokaryotic enzyme was feasible. The crystal structure of the native form, NY-fumarase, encompasses residues R22 through M484, while the recombinant form, RY-fumarase, consists of residues S27 through L485. Both crystal structures lack the N-terminal translocation segment. Each subunit of the homo-tetrameric protein has three domains. The active site is formed by segments from each of three polypeptide chains. The results of these studies on the eukaryotic proteins are unique, since the recombinant form was done in the absence of dicarboxylic acid and has an unoccupied active site. As a comparison, native fumarase was crystallized in the presence of the competitive inhibitor, meso-tartrate. Meso-tartrate occupies a position close to that of the bound citrate molecule found in the active site of the E. colienzyme. This inhibitor participates in hydrogen bonding to an active-site water molecule. The independent determination of the two structures provides further evidence that an active-site water molecule may play an active role in the fumarase-catalyzed reaction.

1.When the surface layers of steel 20KhN3A are saturated in nitriding with nitrogen to 0.6–0.8; 0.4–0.5, and 0.3–0.4% at a distance from the surface of 0.05, 0.3, and 0.6 mm, respectively, a structure forms with high strength, increased amount of residual nitrogen austenite, stability of the martensite to loss of strength and of the residual austenite to ? ? aM transformation both in the surface zones of the case and in the region of action of the reversed tangential contact stresses.2.Strengthening heavy-duty driving pinions of steel 20KhN3A of the final reduction gear of tractors by nitriding with increased nitrogen potential and immediate quenching increases considerably the resistance to contact fatigue, regardless of the fact that the case is thinner than a case obtained by case-hardening with repeated quenching.

1.The addition of 0.001% B increases the scaling resistance of steel Kh23N13 at 900–1100°C (the same as an addition of 0.1–0.2% rare earth metal). Increasing the boron content to 0.0028% lowers the scaling resistance of the steel.2.The effect of boron in the oxidation process appears at the stage of diffusion growth of the oxide layer. It is probable that small boron additions increase the breakaway energy of metal ions from the crystal lattice, which reduces the flow of ions into the scale and reduces the weight gain of steel with 0.001% B.3.The lower scaling resistance of the steel with 0.0028% B is evidently due to the presence of excess phases — undissolved borides and carbides, the interfaces of which have an elevated chemical activity.

The addition of 0.08–0.20% V changes the fine structure of cast steel 45FL after quenching and tempering as compared with steel 45L without vanadium — the mosaic block size decreases and microdistortions increase. The effect of vanadium on the intragranular structure of the steels investigated is greatest at elevated tempering temperatures (550–600°).