M. V. Kovalchuk

Crystal growth of phosphopantetheine adenylyltransferase, carboxypeptidase t, and thymidine phosphorylase on the international space station by the capillary counter-diffusion method

Crystals of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis, thymidine phosphorylase from Escherichia coli, carboxypeptidase T from Thermoactinomyces vulgaris and its mutant forms, and crystals of complexes of these proteins with functional ligands and inhibitors were grown by the capillary counter-diffusion method in the Japanese Experimental Module Kibo on the International Space Station. The high-resolution X-ray diffraction data sets suitable for the determination of high-resolution three-dimensional structures of these proteins were collected from the grown crystals on the SPring-8 synchrotron radiation facility. The conditions of crystal growth for the proteins and the data-collection statistics are reported. The crystals grown in microgravity diffracted to a higher resolution than crystals of the same proteins grown on Earth.

The crystal structure and chemistry of several palygorskite samples with different geneses

The structure, chemical composition, and properties of palygorskites from several deposits in the Russian Federation, Ukraine, Uzbekistan, and Slovakia have been investigated by transmission electron microscopy, microanalysis, X-ray diffraction, IR spectroscopy, and thermal analysis. It is shown that the palygorskites formed under different physicochemical conditions may significantly differ in chemical composition, morphology, and defect structure. Depending on the formation conditions, palygorskites decompose differently upon heating.

X-ray fluorescence methods for investigations of lipid/protein membrane models

The protective effect of the bisphosphonate drug xydiphone (K,Na-ethidronate) on membrane-bound enzyme damaged by lead ions has been studied. A protein/lipid film of Ca-ATPase/phosphatedylethanolamine deposited on a silicon substrate was used as a model system. The position of lead ions within the molecular film before and after the xydiphone treatment was determined using the total-reflection X-ray fluorescence method. This technique is based on the simultaneous measurement of the X-ray reflection and the yield of the fluorescence radiation excited by X-ray inelastic scattering. The possibility of directly locating lead ions is the main advantage of this approach. Xydiphone has been found to effectively eliminate lead ions that have been incorporated into Ca-ATPase molecules during a preliminary incubation in lead acetate solution. The lead ions that were bound at the sites of the Ca-ATPase attachment to the phospholipid monolayer have proved to be inaccessible for xydiphone. A preliminary incubation of Ca-ATPase in the xydiphone solution precluded the incorporation of lead ions into the protein.

X-ray phase-contrast methods

This review is devoted to a comparative description of the methods for forming X-ray phase-contrast images of weakly absorbing (phase) objects. These include the crystal interferometer method, the Talbot interferometer method, diffraction-enhanced X-ray imaging, and the in-line method. The potential of their practical application in various fields of science and technology is discussed. The publications on the development and optimization of X-ray phase-contrast methods and the experimental study of phase objects are analyzed.

X-ray acoustic resonators for controlling the spatial characteristics of X-radiation

The paper presents the results of studying the acoustic characteristics of special X-ray acousto-optical elements designed for precision control of X-ray beam parameters with time resolution. X-ray measurements revealed a number of specific features of oscillations of X-ray acoustic elements not exhibited in standard electromechanical measurements. The existence of these features is confirmed by numerical calculations computations of the acoustic fields in this type of elements.

The belok station for protein crystallography on the synchrotron radiation beam from the bending magnet in the Sibir-2 storage ring

Design modifications made in the initial project of the Belok station in the Sibir-2 storage ring and the alignment and calibration methods are considered. The main operating parameters of the station are reported. Protein single crystals in a capillary at T = 293 K and without a capillary at T = 95 K, powders (angular resolution Δ2ϑ = 0.04°), and nanocrystalline Na and Cl2 precipitates (sizes, shape, and orientation) in electron-irradiated NaCl crystals have been investigated. The problem of focusing of a short-wavelength synchrotron radiation beam with sagittal bending of the second crystal in the double-crystal monochromator at a limited source-to-sample distance is solved in the Belok project.

X-ray total external reflection fluorescence study of LB films on solid substrate

The distribution of heavy ions inside a thin LB film and the structure perfection of organic layers have been studied by registering fluorescence excited by X-ray evanescent/standing wave fields under conditions of total external reflection. The possibility of the application of new complicated artificial multilayer systems as substrates for structure characterization of LB films deposited on them was revealed.

Investigation of Surface-Layer Structure of Single Crystals with Triple-Crystal X-ray Diffractometry

The possibilities of the X-ray triple-crystal diffractometry (TCD) method in studying the tails of rocking curves of both a perfect crystal and a crystal with a disturbed surface layer are shown. It was found that at large deviation angles (a) from the Bragg condition the pseudopeak of the TCD curves significantly exceeds the main peak. The thermal diffuse scattering in the monochromator crystal is discussed as one of the reasons for this effect. This phenomenon is also responsible for the violation of the I(a)ocl/a 2 dependence in double-crystal diffractometry (DCD). By measuring the intensities of the main peaks of TCD curves, it is possible to separate the diffuse and the coherent scattering components in the rocking curves obtained by DCD.

New method for measuring rocking curves in X-ray diffractometry by ultrasonic modulation of the lattice parameter

A method for measuring double-crystal rocking curves with the aid of an X-ray-acoustic analyzer is proposed and implemented. This method makes it possible to perform precise measurements with a high time resolution and without the mechanical rotation of the crystal. The results of testing the method are presented.

New possibilities of the x‐ray standing wave method in multiple diffraction of synchrotron radiation

Results of measurements of the reflected beam intensity and photoelectron yield under conditions of dynamical 111/220 diffraction of synchrotron x‐ray radiation are presented. The experiments were carried out on beam lines 15C and 14B at the Photon Factory. Two possible multicrystal arrangements were used for the preprocessing of the incident beam. In the first one, a double‐crystal Si (111) monochromator was used for monochromation and collimation of the x‐ray beam in the vertical plane and a Si (220) channel‐cut crystal was used for collimation in the horizontal plane. The second crystal arrangement is based on a (111)‐oriented Si crystal adjusted for a six‐beam Laue diffraction condition. The anomalously transmitted (μt/γ0 ≊ 40) beam was used as an incident beam in the x‐ray standing wave measurements. The angular dependence of the total photoelectron yield was measured using a gas flow proportional counter.