Biophysics最新文献

The effect of barium cation doping of octacalcium phosphate powder obtained using a low-temperature method on its phase and structural characteristics, as well as biocompatibility, including under in vitro conditions simulating inflammation, has been studied. It was found that doping with Ba²⁺ cations in the concentration range used (1, 5, and 10 calculated%) does not interfere with the low-temperature chemical transformation of dicalcium phosphate dihydrate and its conversion to octacalcium phosphate; however, the actual substitution is at a maximum of 6.7 at %. The results of in vitro studies show that the replacement of calcium ions with barium ions in the structure of octacalcium phosphate does not lead to an increase in cytotoxic properties; all studied variants of low-temperature octacalcium phosphate and its barium-substituted forms at the recommended concentration of 1 mg/mL do not exhibit toxic effects and are biocompatible. The effects identified for octacalcium phosphate with a maximum degree of Ca²⁺ substitution by Ba²⁺ equal to 10%, namely the absence of an effect on the content of lysosomes and reactive oxygen species in human macrophages under normal conditions and a significant decrease in the production of reactive oxygen species under conditions simulating inflammation, as well as a significant increase in the constitutive activation of T-lymphocytes in vitro, indicate that these processes are directly and dose-dependently associated with Ba²⁺ cations in the composition of octacalcium phosphate. Thus, the proposed method of low-temperature chemical transformation of Ba²⁺-substituted variants of octacalcium phosphate is promising and is of interest for obtaining materials based on calcium phosphate compounds with immunoregulatory properties. The obtained Ba²⁺-substituted variants of octacalcium phosphate are safe and biocompatible, while octacalcium phosphate with the maximum degree of Ca²⁺ substitution by Ba²⁺ is not only bioactive, but also has potential antioxidant and immunomodulatory effects.

A comparative study of indicators of somatic mutagenesis and the thiol disulfide system in the peripheral blood of cancer patients before treatment and healthy individuals with different smoking status (n = 95) has been carried out. All studied parameters including the content of reduced (GSH) and oxidized (GSSG) glutathione and their ratio (GSH/GSSG), the frequency of lymphocytes with mutations at the T-cell receptor (TCR) locus were found to be significantly increased by 1.5–2.7 times in the general group of patients compared to those in the general group of healthy individuals (p < 0.01 in all cases). After cessation of smoking, a decrease in the frequency of mutant cells and the ratio of reduced and oxidized glutathione was observed in patients (p < 0.05). At the individual level, strong correlations were found between the frequency of TCR-mutant cells and the contents of GSH and GSSG only in the subgroup of smoking patients with a high level of mutagenesis. The correlation coefficient between the frequency of TCR-mutant lymphocytes and the GSH content in this subgroup was 0.82 (p < 0.001) and for GSSG r = 0.68 (p < 0.01). The results we obtained indicate the contribution of the thiol disulfide system to the formation of a high frequency of gene mutations in smokers with cancer.

The hydrolysis of adenosine triphosphate to adenosine diphosphate and orthophosphate was simulated using the density functional method. Two systems were considered: an adenosine triphosphate molecule in an aqueous solution and reaction products (adenosine diphosphate, orthophosphate, and H⁺) uniformly surrounded by water (({{n}_{{{{{text{H}}}_{{text{2}}}}{text{O}}}}}) = 80). Calculations have shown that the hydrolysis of adenosine triphosphate is accompanied by a decrease in the total energy of the system, which is consistent with the ideas of the energy-donor nature of the reaction of hydrolysis of adenosine triphosphate to adenosine diphosphate and orthophosphate. In the absence of divalent cations, the decrease in energy as a result of adenosine triphosphate hydrolysis is ΔE = E_ADP+Pi − E_ATP ≈ −110 kJ/mol. Electrostatic interactions due to the presence of divalent cations (Mg²⁺ or Ca²⁺) increase the energy of hydrolysis (ΔE ≈ −135 kJ/mol). The results obtained are discussed in the context of the energy role of adenosine triphosphate in biological systems.

DNA demethylation makes closed regions of the genome available for transcription and thus causes increased activity of mobile genetic elements (transposons) in the genome. The study of the influence of abnormal activity of transposons on cell energy attracts attention due to the potential possibility of using this effect to create an energy deficit with subsequent launch of cell death programs, which may be relevant for the development of anti-cancer strategies. This paper presents the results of experimental measurements of the ATP level in HEK-293 cells obtained from human embryonic kidneys and the MCF-7 breast cancer cell line under normal and demethylation conditions. The HEK-293 line was transfected with a plasmid containing the LINE-1-EGFP genetic construct, and active insertion of the LINE-1 transposon in the transfected cells was shown. Transposon expression in demethylated MCF-7 cells was shown using real-time PCR. The results of ATP measurements demonstrate an increase in energy stores in cells upon both demethylation and transfection with LINE-1-EGFP. The observed effect suggests that the energy load expected from transposon activation is overwhelmed by the energy release from other cellular processes that occur during demethylation and transfection.

A comparative study of the properties of cytochrome c in its interaction with phosphatidic acid is carried out. Similar conformational changes in the active center of cytochrome c occurring during its interaction with both cardiolipin and phosphatidic acid are demonstrated using the methods of spectrofluorometry. The presence of similar magnitudes of peroxidase activity of cytochrome c in its interaction with both cardiolipin and phosphatidic acid was corroborated by luminol-dependent chemiluminescence, and the use of the EPR method enabled the detection formation of phenoxyl radical of etoposide in both complexes. It can be concluded that both phosphatidic acid and cardiolipin effectively alter the structure of the active center of cytochrome c and contribute to the enhancement of its peroxidase activity. The obtained results may indicate a very probable participation of both cardiolipin and phosphatidic acid in the development of cytochrome c–mediated proapoptotic processes in mitochondria.

Flax is an important agricultural crop grown for oil and fiber. Flax fiber is used in various industries and breeding new flax varieties with better fiber characteristics is subject of interest. Genome-wide association studies (GWAS) can find variants associated with traits important for fiber quality, but differences in data due to different growing conditions in different years reduce the power of GWAS methods. The 3VmrMLM method allows one to search for variants in data measured in several environments, allowing one to find new variants not found by other methods. Measurements in different years were taken as different environments; the method found a total of 205 variants characteristic of all or several environments, 37 of which were located in the body of known genes with important functions; the effect of some variants on fiber characteristics was also confirmed in an independent set of plants.

The results of an in situ (leaves) study of electron transport in chloroplasts of two plant species of the genus Cucumis, the shade-tolerant species C. sativus (cucumber) and a light-loving species C. melo (melon) grown under conditions of strong (800–1000 μmoles m^–2 s^–1 of photons) and moderate (50–125 μmoles m^–2s^–1 of photons) illumination are described. The processes of electron transport were monitored by the electron paramagnetic resonance (EPR) signal from ({text{P}}_{{{text{700}}}}^{ + }) (the oxidized reaction center of photosystem 1), by light absorption (the difference signal A_870–830 from ({text{P}}_{{{text{700}}}}^{ + })), and by the fluorescence yield of chlorophyll a. It has been shown that plants grown at high light intensity are characterized by faster changes in the redox state of Р₇₀₀ compared to plants grown at low (moderate) light intensity. The data obtained are discussed in the context of the mechanisms of regulation of electron transport in chloroplasts of shade-tolerant and light-loving plant species of the genus Cucumis.

We demonstrated the temperature heterogeneity of an electrophoretic solution, which is dynamically changing during electrophoresis in the gel platform area, previously. In order to understand the reasons for this effect, we used U-shaped inserts in the wells of the electrophoretic chamber, protruding above the surface of the electrophoretic solution, but not affecting the current flow. The study showed that the migration of heated masses of solution is caused by different rates of hydrogen and oxygen production on platinum electrodes. Using the technique of real-time thermal imaging it was demonstrated that in the presence of U-shaped inserts heating was uniform up to 7°С throughout the entire volume of the solution located above the gel platform. Heating of the liquid in the well area occurred with lower dynamics and was not identical. The heating of the liquid in the cathode well occurs insignificantly (only 1.5°С), while at the anode the increase is 2.5°С. We believe that temperature homogeneity will be of significant importance for reducing the variability of the results obtained by the Comet assay (DNA comet) method on preparations subjected to alkaline electrophoresis.

The following question is considered—why in dinitrosyl iron complexes functioning in living organisms dinitrosyl ligands are represented as the “working form” of endogenous nitric oxide (NO), moreover, in equal proportions of neutral NO molecules and their cationic (NO⁺) form? It is shown that this representation is a direct consequence of the mechanism of formation of dinitrosyl iron complexes occurring in living organisms with the participation of NO molecules, weakly bound ferrous iron and thiol-containing compounds. The fundamental stage of this process is the disproportionation reaction of NO molecules that bind in pairs to the Fe²⁺ ion. As for thiol-containing ligands, their presence in dinitrosyl iron complexes ensures the stabilization of nitrosonium cations that appear in these complexes during the reaction of disproportionation of NO molecules.

Currently, isometric exercises are widely used to increase muscle strength and endurance. They are also used in rehabilitation protocols for people with limited joint mobility after arthroplasty operations. The paper considers the effect of isometric exercises on the morpho-functional characteristics of muscle cells, cytokine secretion by muscle cells, blood circulation and mass transfer in muscle tissue, as well as on bone remodeling and repair. The existing protocols for early rehabilitation of patients after arthroplasty are not optimal and do not take into account the individual characteristics of patients. To develop effective methods of early rehabilitation of patients after arthroplasty, it is necessary to know the biophysical basis of the influence of isometric exercises on the regeneration of muscle and bone tissue.