Том 62, № 6 (2017)

This review presents the instrumental methods used for chemical and phase composition investigation of gallstones. A great body of data has been collected in the literature on the presence of elements and their concentrations, obtained by fluorescence microscopy, X-ray fluorescence spectroscopy, neutron activation analysis, proton (particle) induced X-ray emission, atomic absorption spectroscopy, high-resolution gamma-ray spectrometry, electron paramagnetic resonance. Structural methods—powder X-ray diffraction, infrared spectroscopy, Raman spectroscopy—provide information about organic and inorganic phases in gallstones. Stone morphology was studied at the macrolevel with optical microscopy. Results obtained by analytical scanning and transmission electron microscopy with X-ray energy dispersive spectrometry are discussed. The chemical composition and structure of gallstones determine the strategy of removing stone from the body and treatment of patients: surgery or dissolution in the body. Therefore one chapter of the review describes the potential of dissolution methods. Early diagnosis and appropriate treatment of the disease depend on the development of clinical methods for in vivo investigation, which gave grounds to present the main characteristics and potential of ultrasonography (ultrasound scanning), magnetic resonance imaging, and X-ray computed tomography.

The method for X-ray wavelength tuning using an adaptive element (a quartz monolithic resonator modulated by a standing longitudinal low-frequency ultrasonic wave) has been proposed and implemented. This method is characterized by high tuning accuracy and possibility of scanning X-ray beam parameters with a time resolution of up to 3 μs.

The solid solution NH₄Al_0.62Cr_0.38(SO₄)₂ · 12H₂O was studied by X-ray diffraction. The crystal structure was determined in a series of the maximal subgroups Pa3̄ > R3̄ > P1̄ > P1. Reflections forbidden in sp. gr. Pa3̄ are indicative of symmetry lower than cubic. In the centrosymmetric models under consideration, all sulfate groups are oppositely oriented with respect to each other. In non-centrosymmetric sp. gr. P1, four of the eight sulfate groups have the same orientation, whereas the other four groups are oriented in an opposite direction.

X-ray diffraction study of two crystalline modifications of С₂Н₅O–C₆H₃(OН)–СН=N–C₆H₄–CH₃ (1a, sp. gr. Р2₁/n, and 1b, sp. gr. С2/c) and С₃H₇O–C₆H₃(OН)–СН=N–C₆H₄–C₄H₉ (2, sp. gr. Р2₁2₁2₁) has been performed. The 1a crystal structure contains two independent molecules. The molecules are conformationally nonrigid with respect to the mutual rotation of benzene rings; the dihedral angles between their planes are 29.19° and 26.00° in the independent molecules of 1a, 18.72° in the molecule of 1b, and 50.35° in the molecule of 2. The crystal packing of the compounds is discussed.

In this study, quantum chemical calculations based on the density functional theory have been carried out to examine the effects of N-[4-(3-methyl-3-phenyl-cyclobutyl)-thiazol-2-yl]-N′-pyridin-2-ylmethylene- chloro-acetic acid hydrazide. The calculated values are compared with the experimental data available for these molecules as a mean of validation of our proposed chemistry model. Aided by normal coordinate analysis and potential energy distributions, a confident vibrational assignment of all fundamentals is proposed herein. Additional support is given by ¹H and ¹³C NMR spectra recorded with the sample dissolved in CDCl₃ and by predicted chemical shifts at the B3LYP/6-31G(d)/6-311G+(d) levels obtained using the gauge-invariant atomic orbital method. The calculated HOMO and LUMO energies also confirm that the charge transfer occurs within the molecule. Thiazole-based compounds are potential storehouse for exploiting CH···O and CH···N hydrogen bonding interactions for molecular self-assembly.

An antiaromatic compound 3,4,9,10-tetrahydrodicyclopenta[cd,lm] perylene, was synthesized by a coupling reaction. Its crystal structure was determined by X-ray diffraction. Crystal structures shows that the antiaromatic compounds are aggregated to J-aggregation materials. It further results ultrafast charge separation at organic interface and electron transfer in the aggregation materials. UV-vis spectrum shows that title compound has a broad UV-vis light absorbance at the wavelength range from 250 to 470 nm and a 2.67 eV energy gap value between the highest occupied and the lowest unoccupied molecular orbital energy levels.

A complex structural analysis of nuclear export protein NS2 (NEP) of influenza virus A has been performed using bioinformatics predictive methods and small-angle X-ray scattering data. The behavior of NEP molecules in a solution (their aggregation, oligomerization, and dissociation, depending on the buffer composition) has been investigated. It was shown that stable associates are formed even in a conventional aqueous salt solution at physiological рН value. For the first time we have managed to get NEP dimers in solution, to analyze their structure, and to compare the models obtained using the method of the molecular tectonics with the spatial protein structure predicted by us using the bioinformatics methods. The results of the study provide a new insight into the structural features of nuclear export protein NS2 (NEP) of the influenza virus A, which is very important for viral infection development.

The spatial organization of the genome is controlled by a special class of architectural proteins, including proteins containing BTB domains that are able to dimerize or multimerize. The centrosomal protein 190 is one of such architectural proteins. The purification, crystallization, and preliminary X-ray diffraction study of the BTB domain of the centrosomal protein 190 are reported. The crystallization conditions were found by the vapor-diffusion technique. The crystals diffracted to 1.5 Å resolution and belonged to sp. gr. P322₁. The structure was solved by the molecular replacement method. The structure refinement is currently underway.

The three-dimensional structure of the D456A mutant of the nicking endonuclease Nt.BspD6I was determined. According to the concept of the cleavage scaffold, the replacement of D456 by A456, which resulted in complete (100%) loss of nickase activity, was shown to be a trigger of structural changes in the cleavage-scaffold region. Besides, the displacement of Е482 and the rotation of Н449 toward the N-terminal domain initiate conformational changes in the D1 recognition subdomain of the N-terminal domain with the result that the centers of mass of the С- and N-terminal domains are brought into close proximity to each other. Electrostatic calculations showed that changes in the free energy and electrostatic interactions for the mutant nickase are distributed predominantly in the N-terminal domain and that these changes are not attenuated in a radial fashion away from the mutation site but have a distinct direction.

The microhardness and thermal stability of K₂Co_xNi₁–_x(SO₄)₂ · 6H₂O mixed crystals have been investigated. Microhardness peaks and dehydration onset temperatures are found in the composition range x = 0.05–0.23. The observed anomalies of properties are related to the anomalous changes in the structural parameters of the crystals in this composition range with an increase in the cobalt content. It is shown that structural imperfection of the crystals depends on the sectorial inhomogeneity and reaches a maximum at x = 0.43–0.54.

The structure and electrical and optical properties of β-Ga₂O₃–In₂O₃ thin films on sapphire substrates with different orientations have been investigated. The samples have been prepared by annealing of gallium–indium metallic films on sapphire substrates in air at different gallium-to-indium ratios in the initial mixture. The photoconductivity of these structures in the solar-blind ultraviolet spectral region has been examined.

Complex studies of magnetic periodic metallic systems based on Dy/Gd layers have been carried out by X-ray diffraction, resonance X-ray reflectometry, transmission electronic microscopy, and energydispersve microanalysis. The application of these methods and joint analysis of their results provide an effective approach to study of the structure and determination of the parameters of individual layers and interfaces and their structural quality with a high degree of reliability.

Cobalt nanoparticles (3–7 nm in size) obtained by cobalt carbonyl decomposition in 1,2-dichlorobenzene in the presence of surfactants (trioctylphosphine oxide and oleic acid) have been studied by a complex of structural methods: small-angle X-ray scattering, electron diffraction, and transmission electron microscopy. The nanoparticles synthesized are found to consist of the cubic ε-Со phase; their crystal structure is described within the sp. gr. P4₁32, a = 6.097 Å. Using small-angle X-ray scattering, the size and shape of nanoparticles have been determined directly in the liquid dispersion. Most of the particles have a spherical shape; their average size is ≈3.5 ± 0.5 nm, which agrees with the electron microscopy data. Possible factors causing the ε-phase formation during synthesis of metallic Co nanoparticles are discussed.

A comparative analysis of the relationship between the morphological forms and magnetic properties of natural goethite particles from the crust of weathering of the Far East and Vietnam basalts and pure, chemically synthesized goethite particles was performed using Mössbauer spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. It is shown how the shape of biogenic goethite particles affects their magnetic properties, which significantly differ from the magnetic properties of chemically synthesized samples.

Data on the morphology and normal growth rate of the (110) and (001) faces, velocities of step motion, and slopes of dislocation hillocks on the (001) face of K₂Co_xNi₁–_x(SO₄)₂ · 6H₂O crystals at different supersaturations of solutions with a Co/Ni ratio equal to 1: 1 or 1: 2 have been obtained using a Michelson interferometer. The morphology of the (110) faces is found to be the same for solutions of both compositions. Powerful dislocation sources with large Burgers vectors dominate on the (001) face. The morphology of the (001) surface is rougher than that of (110), especially in a 1: 2 solution at high supersaturation. The (110) faces grow more slowly as compared with (001). The kinetic coefficients of steps on the (001) face are identical in the 1: 1 and 1: 2 solutions. The influence of the kinetic and morphological characteristics of (001) faces on the single-crystal quality is analyzed.

A comparative estimation of the size parameters of clusters of precrystallization liquid phase (PLP) of metals and critical crystalline nuclei has revealed the sizes of critical crystalline nuclei to be smaller than those of PLP clusters. Based on the results of estimation of the radii of critical crystalline nucleus by the methods of classical theory and molecular dynamics, it has been found for the first time that the radius of critical crystalline nucleus is about 0.2–0.4 of the PLP cluster radius. This fact confirmed the hypothesis of Ubellode et al. about the formation of a transition layer with a partially ordered structure between the solid and liquid phases. A scheme of the nucleation and growth of a crystalline nucleus under conditions of transition layer formation is proposed.

A new time-of-flight neutron reflectometer GRAINS with a horizontal sample plane (vertical scattering plane) has recently been put into operation at the pulsed reactor IBR-2 (JINR, Dubna). The scattering geometry applied makes it possible to carry out complex studies of nanostructured interfaces in solid and liquid states by measuring the specular reflectivity and the intensity of diffuse scattering of thermal neutrons from open surfaces and hidden interlayer boundaries, including solid-liquid interfaces, over a wide momentum transfer range. The classical analysis of specular reflectivity allows one to determine the scattering length density profile in the object under study in a direction perpendicular to the interface for a thickness of ~100 nm with a resolution of 1 nm. The analysis of off-specular (diffuse) neutron scattering makes it possible to characterize lateral correlations on surfaces and interlayer boundaries. The paper summarizes the first experience in the operation of the GRAINS reflectometer. The instrument characteristics are presented together with the possibilities for experiments with solid and liquid samples illustrated with simple systems. Further steps for the development of the reflectometer are discussed.

An approach to the description of local atomic disorder (short-range order) in single crystals by the mixed-symmetry method based on Bragg scattering data is proposed, and the corresponding software is developed. In defect-containing crystals, each atom in the unit cell can be described by its own symmetry space group. The expression for the calculated structural factor includes summation over different sets of symmetry operations for different atoms. To facilitate the search for new symmetry elements, an “atomic disorder expert” was developed, which estimates the significance of tested models. It is shown that the symmetry lowering for some atoms correlates with the existence of phase transitions (in langasite family crystals) and the anisotropy of physical properties (in rare-earth dodecaborides RB₁₂).