Small-angle X-ray scattering study of the influence of solvent replacement (from H<Subscript>2</Subscript>O to D<Subscript>2</Subscript>O) on the initial crystallization stage of tetragonal lysozyme

The composition of lysozyme solutions in D₂O under conditions favorable for the formation of tetragonal crystals has been investigated at different protein concentrations by small-angle X-ray scattering using the synchrotron radiation. In addition to lysozyme monomers, dimeric and octameric species are found in the crystallization solutions; the octamer content increases with an increase in the protein concentration. A comparison of the data with those obtained under similar conditions but with H₂O used as a solvent has shown that the replacement of light water with heavy one leads to increase of octamer volume fraction in solution.     

Effect of severe plastic deformation by torsion on the properties and structure of the Ni54Mn21Ga25 and Ni54Mn20Fe1Ga25 alloys

The effect of one-percent substitution of iron for manganese on the physical (magnetic, electrical, thermal, and galvanomagnetic) properties and the crystal structure of the Ni₅₄Mn₂₁Ga₂₅ alloy has been investigated. It has been demonstrated that the deviation of the alloy composition from the stoichiometric composition Ni₅₀Mn₂₅Ga₂₅ leads to the formation of a mixed ferromagnetic-antiferromagnetic state. The atomic disordering and nanostructuring of the alloys under investigation due to the severe plastic deformation by torsion in Bridgman anvils to sizes of 10–20 nm result in the suppression of reversible magnetically controlled shape memory effects.     

Thermal stability of organic layered systems based on lead stearate

The structural variation in multilayer Langmuir-Blodgett films of lead stearate caused by heat treatment under different conditions in the temperature range 20–100°C is investigated by X-ray reflectometry and high-resolution electron diffraction. Successive annealing of the samples is shown to not alter the initial layered structure at temperatures of 60, 80, and 100°C; partial disturbance of the layered structure occurs upon successive annealing at 80°C and 100°C. Significant disturbance of the structure is observed when the films are heated immediately to 100°C. In all these cases, the orthorhombic (pseudomonoclinic) lattice, with the lattice constants: a = 0.496, b = 0.738, c = 9.60 nm, α = β = γ = 90°, space group P2/1b, formed by transferring monolayers onto the substrate is retained in the crystalline domains of the film.     

Effect of cobalt doping on thermoelastic martensitic transformations and physical properties of magnetic shape memory alloys Ni50 − x Co x Mn29Ga21

The magnetic and thermoelastic martensitic transformations and physical properties (magnetization, electrical resistivity, thermoelectric power, relative elongation, and thermal expansion coefficient) of multicomponent magnetic shape memory alloys Ni_{50 ? x} Co _x Mn₂₉Ga₂₁ (x = 0, 1, 2, 3, 10 at %) have been investigated. The critical temperatures of thermoelastic martensitic transformation and magnetic transitions have been determined. It has been found that the alloy with 10 at % Co undergoes a martensitic transformation in the temperature range of 6–10 K.     

Formation of partially ordered organic planar systems based on the in situ control of their structural organization

The possibilities of significantly improving the quality of planar systems based on photoactive porphyrin–fullerene dyads, layers based on cytochrome c and cardiolipin, and lysozyme crystals and films using a complex of in situ X-ray methods and simulation are described. The potential of X-ray phase-sensitive and surface-sensitive methods developed by M.V. Koval’chuk and researchers from his school in monitoring all stages of synthesis of partially ordered organic structure is demonstrated. This approach shows its efficiency for in situ studies: starting from the formation of complexes in solutions up to the growth of protein films and crystals.     

X-ray diffraction and X-ray standing-wave study of the lead stearate film structure

A new approach to the study of the structural quality of crystals is proposed. It is based on the use of X-ray standing-wave method without measuring secondary processes and considers the multiwave interaction of diffraction reflections corresponding to different harmonics of the same crystallographic reflection. A theory of multiwave X-ray diffraction is developed to calculate the rocking curves in the X-ray diffraction scheme under consideration for a long-period quasi-one-dimensional crystal. This phase-sensitive method is used to study the structure of a multilayer lead stearate film on a silicon substrate. Some specific structural features are revealed for the surface layer of the thin film, which are most likely due to the tilt of the upper layer molecules with respect to the external normal to the film surface.     

Formation of long-period nanostructural phases in Ni<Subscript>2</Subscript>MnGa-based <Emphasis Type="Italic">L</Emphasis>2<Subscript>1</Subscript> alloys with thermoelastic martensitic transitions

The crystalline structures of martensite phases in Ni₂MnGa-based ternary alloys have been studied in a wide range of temperatures and compositions transmission and scanning electron microscopy, X-ray diffraction, and electron diffraction. It is found that long-period nanostructural phases with thin-plate morphology are formed as a result of martensitic transformation in Ni₂MnGa-based alloys.     

Small-angle X-ray scattering study of conditions for the formation of growth units of protein crystals in lysozyme solutions

The structural composition of lysozyme solutions favorable for the formation of the tetragonal form of protein crystals was studied by synchrotron-based small-angle X-ray scattering depending on the protein concentration and the temperature. Along with lysozyme monomers, dimers and octamers are found in crystallization solutions; the octamer content increases with an increase in the protein concentration.     

In situ study of the growth and degradation processes in tetragonal lysozyme crystals on a silicon substrate by high-resolution X-ray diffractometry

The results of an in situ study of the growth of tetragonal lysozyme crystals by high-resolution X-ray diffractometry are considered. The crystals are grown by the sitting-drop method on crystalline silicon substrates of different types: both on smooth substrates and substrates with artificial surface-relief structures using graphoepitaxy. The crystals are grown in a special hermetically closed crystallization cell, which enables one to obtain images with an optical microscope and perform in situ X-ray diffraction studies in the course of crystal growth. Measurements for lysozyme crystals were carried out in different stages of the crystallization process, including crystal nucleation and growth, developed crystals, the degradation of the crystal structure, and complete destruction.