Details about molecular membrane dynamics in living cells, such as lipid-protein interactions, are often hidden from the observer because of the limited spatial resolution of conventional far-field ...optical microscopy. The superior spatial resolution of stimulated emission depletion (STED) nanoscopy can provide new insights into this process. The application of fluorescence correlation spectroscopy (FCS) in focal spots continuously tuned down to 30 nm in diameter distinguishes between free and anomalous molecular diffusion due to, for example, transient binding of lipids to other membrane constituents, such as lipids and proteins. We compared STED-FCS data recorded on various fluorescent lipid analogs in the plasma membrane of living mammalian cells. Our results demonstrate details about the observed transient formation of molecular complexes. The diffusion characteristics of phosphoglycerolipids without hydroxyl-containing headgroups revealed weak interactions. The strongest interactions were observed with sphingolipid analogs, which showed cholesterol-assisted and cytoskeleton-dependent binding. The hydroxyl-containing headgroup of gangliosides, galactosylceramide, and phosphoinositol assisted binding, but in a much less cholesterol- and cytoskeleton-dependent manner. The observed anomalous diffusion indicates lipid-specific transient hydrogen bonding to other membrane molecules, such as proteins, and points to a distinct connectivity of the various lipids to other membrane constituents. This strong interaction is different from that responsible for forming cholesterol-dependent, liquid-ordered domains in model membranes.
Expansins are small proteins that play a key role in modifying the structure of the cell wall during various physiological processes, in particular cell growth by elongation. Expansins are encoded by ...a large multigene family and are divided into four subfamilies, the main ones being alpha- and beta-expansins; the latter have received special development in cereals. Expansins are thought to modify the interactions of cellulose with xyloglucan (alpha-expansins) or with arabinoxylan (beta-expansins). At the same time, expansins do not have catalytic activity, the specific mechanism of their action is unclear, same as the physiological significance of such a wide variety of isoforms. To study the expression patterns of individual expansins, we conducted a transcriptomic analysis of all expansin genes identified in the maize genome using a convenient model system—zones of the maize growing primary root that differ in the stage of cell development and the composition of their cell walls. Of the 91 maize expansin genes, 67 were expressed in the root, and most expansin genes were characterized by a narrow range of zones with maximum transcript levels. Using a glycoarray containing 183 polysaccharides from the cell walls of plants of various species, we demonstrated that recombinant expansins AtEXPA1 and AtEXPB1 are able to bind to arabinogalactans and rhamnogalacturonans I and a number of other cell wall polysaccharides, which expands the list of their potential carbohydrate targets. Differences in the specificity of the interaction of alpha- and beta-expansins with various polysaccharides, both quantitatively and qualitatively, have been demonstrated. It has been hypothesized that the abundance of expansins in one plant organism and the fine regulation of their expression can be explained, at least in part, by the specific binding of individual expansins to specific cell wall polysaccharides.
The oxidative effects of nonthermal atmospheric–pressure argon plasma, which is an ionized gas produced under the action of microwave, are considered. The applicability of a ferrous sulfate dosimeter ...(Fricke dose meter) for measuring the oxidation properties of nonthermal plasma has been studied. It is shown that, under the influence of nonthermal plasma in a sample of a ferrous sulfate dosimeter, oxidants are formed, determined by the transition of iron from the divalent to trivalent state (the absorption peak at a wavelength of 304 nm). This allows us to conclude that a ferrous sulfate dosimeter can be used to quantify the oxidative potential of nonthermal plasma.
An improved mathematical model was constructed to describe the geometrically and physically nonlinear deformation of specimens of a fiber-reinforced plastic with a rectangular cross-section. The ...specimens had thin elastic side tabs on the clamping ends in the test fixture to transfer the external load to the specimens in kinematic loadings (by the friction forces that arise between the tabs and rigid elements of the test fixture). The specimens had the form of a three-layered rod. For the tabs, the S. P. Timoshenko shear model taking into account the transverse compression was used. For the middle layer across the thickness, a linear approximation for the transverse displacement and a cubic approximation for the axial displacement were accepted. The kinematic relations and equilibrium equations of the theory were obtained based on geometrically nonlinear relations of elasticity theory in a simplified quadratic approximation. They contained geometrically nonlinear terms that, having the necessary degree of accuracy and content, make it possible to identify the classical bending and nonclassical transverse shear buckling modes of the specimens during their compression tests. For unidirectional fiber-reinforced plastics, the physical nonlinearity was taken into account only in the relationship between the transverse shear stress and the corresponding shear strain. When compressing a ±45 fiber-reinforced plastic, the physical nonlinearity was also taken into account in the relation between the normal stress in the specimen cross-section and the corresponding axial strain.
In the first part of the article 1, a physically and geometrically nonlinear boundary-value problem, that describes the compression of a fiber-reinforced plastic rod with 0
s
layup, was formulated. ...The rod had a rectangular cross-section and thin elastic side tabs. The boundary-value problem was reduced to a system of integral-algebraic equilibrium equations containing Volterra integral operators of the second type. To find its numerical solution, the method of finite sums in the variant of integrating matrices was used. The advantage of the method is the possibility of a strong local thickening of the computational grid in the region of large gradients of solutions. Based on the algorithm constructed, an application software package was developed. The results of computational experiments showed that the test specimens under compression according to one of the most commonly used test schemes predominantly failed when the localized transverse shear stresses reached their ultimate values. Failure was also possible according to the shear buckling mode in stress concentration zones. The identification of such modes was possible by using a proposed refined geometrically and physically nonlinear deformation model built in the quadratic approximation with account of transverse shear strains and transverse compression. To verify the numerical method developed, physical experiments were carried out on unidirectional carbon-fiber-reinforced specimens with 0
s
layup. They showed a good agreement between the theoretical and experimental results of the research.
The formulation of the acoustoelasticity problem is given on the basis of refined motion equations of orthotropic plates. These equations are constructed in the first approximation by reducing the ...three-dimensional equations of the theory of elasticity to the two-dimensional equations of the theory of plates, where the approximation of the transverse tangential stresses and the transverse reduction stress is made with the help of trigonometric basis functions in the thickness direction. Wherein at the points of the boundary (front) surfaces, the static boundary conditions of the problem for tangential stresses are satisfied exactly and for transverse normal stress — approximately. Accounting for internal energy dissipation in the plate material is based on the Thompson—Kelvin—Voigt hysteresis model. In case of formulating problems on dynamic processes of plate deformation in vacuum, the equations are divided into two separate systems of equations. The first of these systems describes non-classical shear-free, longitudinal-transverse forms of movement, accompanied by a distortion of the flat form of cross sections, and the second system describes transverse bending-shear forms of movement. The latter are practically equivalent in quality and content to the analogous equations of the well-known variants of refined theories, but, unlike them, with a decrease in the relative thickness parameter, they lead to solutions according to the classical theory of plates. The motion of the surrounding the plate acoustic media is described by the generalized Helmholtz wave equations, constructed with account of energy dissipation by introducing into consideration the complex sound velocity according to Skudrzyk.
Early Ontogeny of Introduced Hydrangea Species Murzabulatova, F. K.; Shigapov, Z. Kh; Polyakova, N. V.
Russian journal of developmental biology,
03/2021, Letnik:
52, Številka:
2
Journal Article
Recenzirano
This work describes early ontogeny of
Hydrangea
L. species introduced into the Bashkir Cis-Urals. In
Hydrangea,
the four distinct age-states of the virginile ontogenetic period, namely seedlings, ...juveniles, immatures and mature vegetative plants, were identified and their morphologic features and development chronology were described. Hydrangeas become juvenile, on average, 25 days after germination, as the second true pair of leaves appears; they enter an immature state in their third year of life, as their stem starts branching, and proceed to a mature vegetative state as basal shoots emerge at the base of the plant, which thus attains its adult shrub life-form.
The paper summarizes data on the lithological and elemental composition of bottom sediments and permafrost from boreholes 1D-14, 3D-14, and 1D-15 drilled from shore ice in Buor-Khaya Bay in ...2014–2015. Based on the determined percentage content of SiO
2
, Al
2
O
3
, Fe
2
O
3
, TiO
2
, MgO, Na
2
O, K
2
O, CaO, MnO, P
2
O
5
, Cl, Cr, S, Ni, Cu, Zn, Rb, Sr, Ba, Y, Zr, and C
org
in sediments, the values of lithochemical moduli were calculated, and a comparative analysis of the lithological and geochemical composition was performed. Differences in the lithochemical composition between the coastal (1D-14 and 3D-14) and relatively distant (1D-15) strata were shown, explained by the spatiotemporal variability of sedimentary fluxes and the weathering crust activity in the studied area of the Laptev Sea. Based on the geological structure, the obtained data on the lithochemical composition of thawed and permafrost deposits indicated that sedimentary rocks in the Kharaulakh Ridge of the Verkhoyansk mountain system, corresponding to sandstones, siltstones, and mudstones, were probably the basis of the petrofund. The contribution of igneous and metamorphic rocks to the supply of sedimentary matter in the strata uncovered by drilling was insignificant and of a subordinate nature.
Analytical solutions of the problem on free vibrations of an orthotropic cuboid with free faces, based on the use of trigonometric functions as base ones in all three directions, are constructed. It ...is established that the solutions obtained describe the purely shearless vibration modes occurring in the body considered at particular ratios between its faces and physicomechanical characteristics of its material. It is shown that, on passing to the zero harmonics in one or two directions, or at zero values of six or all Poisson ratios, the solutions constructed are reduced to the equations corresponding to the classical theory of plates or rods. It is established that, at certain geometrical and physicomechanical parameters, the body considered can have natural frequencies much lower than the known ones.
Manganese-doped nanostructured composites based on TiO
2
were obtained by the template sol–gel method. By a set of investigation techniques, it was established that manganese doping leads to the ...appearance of a rutile phase, which grows with increasing manganese content. It was found that during the template sol–gel synthesis of the TiO
2
/Mn composite, the doping element is not only incorporated into the titanium dioxide structure, but also forms separate phases on its surface. Study of the magnetic characteristics of the obtained composites revealed ferromagnetic ordering at room temperature, while lowering the temperature leads to an increase in the coercive force and appearance of the ferromagnet/antiferromagnet type exchange interaction. A magnetic transition at about 43 K, associated with the transfer of Mn
3
O
4
nanoparticles to the ferromagnetic state, was detected in the composites. Undoped titanium dioxide showed a high photocatalytic activity in the visible spectral range, providing 98% degree of indigo carmine degradation. Manganese doping of TiO
2
microtubes inhibited the photocatalytic activity.
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