Refined Structure of Langmuir Lysozyme Films on Single-Crystal Silicon Wafers According to X-Ray Reflectivity Data

Crystallography Reports - Thin lysozyme films on single-crystal silicon wafers have been studied by X-ray reflectivity. The films have been formed using the modified Langmuir–Schaefer method...     

Observation of strong virtual scattering under three-beam (220, 371) X-ray diffraction in TeO<Subscript>2</Subscript> single crystal

A strong effect of virtual scattering has been experimentally observed when studying the nearly coplanar three-beam (220, 371) X-ray diffraction in a paratellurite single crystal under high-resolution double-crystal X-ray diffraction using MoK _α1 radiation. One characteristic feature of this effect is that the angular dependence of the first (strong) reflection intensity and its shape barely change in the three-beam range of parameters, whereas very strong changes are observed for the second (weak) reflection not only in the three-beam range but also far beyond it, which is related to the variation in the two-beam diffraction parameter due to virtual scattering. The changes observed are asymmetric and make it possible to determine the triplet combination of structure-factor phases.     

Aging of Whey Gels in the Presence of Organic Colloids

Effects of organic colloids on gelation of curds and aging of whey gels are studied. The influence of some physicochemical factors on the predicted macrokinetic characteristics of whey gels is revealed.     

Measurement of piezoelectric constants of lanthanum-gallium tantalate crystal by X-ray diffraction methods

A method for measuring piezoelectric constants of crystals of intermediate systems by X-ray quasi-multiple-wave diffraction is proposed and implemented. This technique makes it possible to determine the piezoelectric coefficient by measuring variations in the lattice parameter under an external electric field. This method has been approved, its potential is evaluated, and a comparison with high-resolution X-ray diffraction data is performed.     

Modification of the Langmuir–Schaefer method for fabrication of ordered protein films

A modification of the Langmuir–Schaefer method for the fabrication of high-quality protein films on a solid substrate was proposed and applied to lysozyme. The procedure relies on the use of a pre-prepared protein solution, the parameters of which correspond to crystallization conditions. A lysozyme Langmuir monolayer was shown to be formed with the involvement of complexes, namely, dimers and octamers of protein molecules that are present in such protein solutions. These complexes apparently retain the structure after spreading a protein solution onto an aqueous subphase in a Langmuir trough. The thickness of the film after the transfer of the monolayer, which was formed by the proposed procedure, onto a solid substrate corresponds to the diameter of the octamer and this film is dense, continuous, and uniform, as was demonstrated by several methods: X-ray reflectivity, total external reflection X-ray standing wave, and atomic force microscopy. A layer of chloride ions that formed under the Langmuir monolayer was found at the air–protein film interface. This fact confirms an important role of the precipitating agent (chloride ions) in all steps of the formation of lysozyme films.     

Study of the specific features of single-crystal boron microstructure

A complex study of the structure of β-boron single crystal grown by the floating-zone method, with sizes significantly exceeding the analogs known in the literature, has been performed. The study includes X-ray diffraction analysis and X-ray diffractometry (measurement of pole figures and rocking curves), performed on both laboratory and synchrotron sources; atomic-resolution scanning transmission electron microscopy with spherical aberration correction; and energy-dispersive microanalysis. X-ray diffraction analysis using synchrotron radiation has been used to refine the β-boron structure and find impurity Si atoms. The relative variations in the unit-cell parameters a and c for the crystal bulk are found to be δa/a ≈ 0.4 and δc/c ≈ 0.1%. X-ray diffractometry has revealed that the single-crystal growth axis coincides with the [\(2\bar 2013\)] crystallographic axis and makes an angle of 21.12° with the [0001] threefold axis. Electron microscopy data have confirmed that the sample under study is a β-boron crystal, which may contain 0.3–0.4 at % Si as an impurity. Planar defects (stacking faults and dislocations) are found. The results of additional measurements of the temperature dependence of the thermal conductivity of the crystal in the range of 50–300 K are indicative of its high structural quality.     

Modern Trends in the In Vitro Production and Use of Callus,Suspension Cells and Root Cultures of Medicinal Plants

This paper studies modern methods of producing and using callus, suspension cells and root cultures of medicinal plants in vitro. A new solution for natural product production is the use of an alternative source of renewable, environmentally friendly raw materials: callus, suspension and root cultures of higher plants in vitro. The possibility of using hairy root cultures as producers of various biologically active substances is studied. It is proven that the application of the genetic engineering achievements that combine in vitro tissue culture and molecular biology methods was groundbreaking in terms of the intensification of the extraction process of compounds significant for the medical industry. It is established that of all the callus processing methods, suspension and root cultures in vitro, the Agrobacterium method is the most widely used in practice. The use of agrobacteria has advantages over the biolistic method since it increases the proportion of stable transformation events, can deliver large DNA segments and does not require special ballistic devices. As a result of the research, the most effective strains of agrobacteria are identified.     

Coplanar three-beam X-ray diffraction study in TeO<Subscript>2</Subscript> single crystal using synchrotron radiation

The results of the first experimental study of coplanar three-beam X-ray diffraction in a paratellurite (TeO₂) single crystal using synchrotron radiation on a Kurchatov synchrotron radiation source are presented. Four cases with (220, 371), (220, 464), (220, 370), and (110, 557) indices have been investigated. In all cases the change of the rocking curve shape of the weak reflection has been observed due to the multibeam interaction resulting in the appearance of two peaks in the reflection curve corresponding to two scattering mechanisms: amplitude and resonance. The origin of the insufficient resolution in the experiments has been considered. It has been shown that the obtained data correspond to the results of the computer simulation.