Biophysics最新文献

To date, there are a huge number of mutant variants described for the TPM1 gene, which encodes the cardiac isoform of tropomyosin (Tpm1.1). The effect of amino acid substitutions Ile92Met and Glu97Gln on the properties of Tpm1.1 was investigated. To establish the possible pathogenicity of these mutant variants, the authors obtained preparations of recombinant proteins of the cardiac isoform Tpm1.1 with amino acid substitutions and studied their effect on the structure of the tropomyosin molecule, on its interaction with F‑actin, and on the functional properties of mutant Tpms as part of a reconstructed thin filament in an in vitro motility assay. Using circular dichroism spectroscopy and differential scanning calorimetry, it was shown that both mutations reduce the stability of the tropomyosin molecule. These mutations led to changes in the parameters of the interaction of myosin with a thin filament in an in vitro motility assay. The most pronounced effect was observed for Tpm1.1 E97Q. The E97Q mutation led to a significant increase in the calcium sensitivity of the myosin-actin interaction of thin reconstructed filaments, which also show residual movement at low calcium concentrations in an in vitro motility assay. The replacement of I92M significantly reduced the rate of movement of thin filaments into the in vitro motility assay and the cooperative interaction of myosin with actin. The obtained data make it possible to confirm the pathogenic status of these mutations, which can be taken into account for correction of cardiac disorders among patients with these genetic changes.

The kinetics of oxidative hemolysis of a 0.2% mouse erythrocyte suspension under the action of radical-forming initiators, hydrogen peroxide (HP), 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), tert-butyl hydroperoxide (t-BuOOH), and cumene hydroperoxide (Cumyl-OOH), was studied over a wide concentration range. Erythrocyte hemolysis occurred upon activation of lipid peroxidation (LPO) in erythrocyte membranes. Hemolytic activity was characterized by the hemolysis induction period (I₁₀), which was determined graphically by the time it took to reach 10% hemolysis. The hemolytic effect of AAPH, t‑BuOOH was concentration-dependent. No concentration dependence was observed for HP and Cumyl-OOH. The known antioxidants 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) potassium propionate (fenosan), 6-methyl-2-ethyl-3-hydroxypyridine hydrochloride (epigid), and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (Tempol) caused a concentration-dependent increase in the hemolysis induction period for both AAPH- and t-BuOOH-dependent initiation. The developed model of induced oxidative hemolysis can be used for testing the new pharmacological substances to antioxidant activity.

Changes in the morphology and state of the cytoplasm of the unicellular alga Scenedesmus quadricauda cells in vitro, as well as the conformation of the chloroplast pigment (carotenoid) under the effect of the pesticide clothianidin, were studied using laser interference microscopy and Raman spectroscopy. It was found that the effect of clothianidin on algae causes changes in the morphology and state of the cytoplasm of cells, as well as the conformation of carotenoids, which correlate with changes in intracellular pH. The action of the pesticide and the protonophore similarly changes the conformation of the carotenoid molecule in the chloroplast due to the fact that in the presence of clothianidin, direct electron transfer from ({text{Q}}_{{text{A}}}^{ - }) to Q_B slows down, the proportion of photosystem II centers with an unoccupied Q_B binding site increases, and the rate of oxidation of ({text{Q}}_{{text{A}}}^{{}}) decreases, probably because of a decrease in the binding rate of plastoquinone with the Q_B site in photosystem II.

Any living organism is an information and energy system. Various definitions of the terms “energy” and “information” are given. The discussions that arise during their definition are considered. The reason for these discussions is explained. The biophysical interpretation underlying these terms is given. The purpose of this article is to explain the dynamics of changes in the connection between energy and information in living systems at a publicly understandable level based on a biophysical description.

The article is devoted to the description of molecular processes that can participate in both proapoptotic and proferroptotic reactions. Using spectrofluorimetry, it was shown that cytochrome c in the presence of phosphatidic acid or cardiolipin binds to the biological membrane approximately four times more strongly than to lecithin. As a result of this interaction, there is an increase in both cytochrome c peroxidase activity (by six and 22 times for complexes with phosphatidic acid and cardiolipin, respectively) and in lipid peroxidation (by three and 17 times for complexes with phosphatidic acid and cardiolipin, respectively). Cytochrome c-induced lipid peroxidation is observed in a narrow range of cytochrome c concentrations near 0.5 μM. In addition, a decrease in the activation and production of reactive oxygen species by peritoneal neutrophils (reduction by 40 and 60%, respectively) was demonstrated under the action of cytochrome c complexes with phosphatidic acid or with cardiolipin. It is assumed that processes occurring with an increase in the intensity of both cytochrome c peroxidase reactions and cytochrome c-induced lipid peroxidation may occur during apoptosis or ferroptosis.

Resveratrol is a natural polyphenol with antibacterial, antifungal, antiviral, and antitumor activity. The mechanisms of resveratrol action require detailed study. In the present work, the ability of resveratrol to penetrate into the nuclei of mammalian cells and bind to DNA there was proven. It was found that in vitro resveratrol changes the conformation of the linker regions of DNA in chromatosomes containing linker histone H1.5, in contrast to chromatosomes with histone H1.0. It was found that resveratrol reduces the ability of the FACT/Nhp6 protein complex to reorganize nucleosomes and blocks the restoration of their structure after dissociation of FACT/Nhp6. The data obtained suggest that resveratrol may influence processes within the cell nucleus by interacting with DNA and altering the interaction between nucleosomes and chromatin-remodeling proteins. Potentially, it may also affect H1.5-dependent gene regulation.

The endothelial monolayer of the inner surface of blood vessels plays a fundamental role in maintaining the integrity of the vascular system and tissue homeostasis by regulating local blood flow and other physiological processes. Endothelial cells are very sensitive to mechanical stress, including gravitational stimuli. Given the involvement of the endothelium in the regulation of the state and functions of blood vessels undergoing changes during space flight, it is extremely important to study the mechanisms of the response of endothelial cells, including at the level of microparticles they secrete to microgravity conditions. The proteome of human umbilical vein endothelial cell microparticles (HUVEC) cultured under static conditions and while modeling the effects of microgravity using a random positioning machine has been studied by chromatography-mass spectrometry using a system consisting of an Agilent 1100 chromatograph and an LTQ-FT Ultra hybrid mass spectrometer. It has been revealed that cells under the influence of microgravity conditions secrete microparticles containing focal adhesion proteins, adapter proteins, and proteins involved in the organization of the cytoskeleton. In general, the percentage of proteins in samples cultured using a random positioning machine is higher for processes related to proinflammatory activation and immunity as well as signaling to the cytoskeleton. Based on these data, it can be assumed that, under microgravity conditions, a proinflammatory response develops and focal contacts are destroyed, which together is a prerequisite for the development of endothelial dysfunction.

The growth-stimulating property of a new compound, 2-ethyl-6-methyl-3-hydroxypyridinium carnitinate, has been studied for the effectiveness of pre-sowing treatment of wheat seeds in order to increase the volume and quality of the crop. The compound showed high antiradical and antioxidant activity, which indicates that it has growth-stimulating and anti-stress properties. The biological activity of the synthesized 2-ethyl-6-methyl-3-hydroxypyridinium carnitinate in the growth of green mass and roots of wheat seedlings at an early stage of germination was studied in order to predict the growth-stimulating properties of wheat development under conditions of pre-sowing seed treatment. It has been shown that the treatment of seeds of soft spring wheat of the zoned variety “Iren” with the compound increases the germination rate, promotes the formation of smooth and simultaneous shoots of plants in the field, good survival of seedlings and increased grain yields. The qualitative composition of the grain of the resulting harvest (2024) was studied for the content of the main components of grain, namely protein, starch, gluten and other important indicators for the bakery industry. The structural and thermodynamic characteristics of wheat starches extracted from seeds treated with the compound were evaluated.

The hippocampus of mice that had been on a high-fat diet for a long time (up to 12 months) was studied. The control group of animals received standard laboratory food. The object of the study was lipofuscin, an undegradable autofluorescent pigment that forms intracellular aggregates in the cytoplasm and lysosomes of long-lived postmitotic cells. Unlike proliferative cells, which effectively dilute the lipofuscin pool by dividing, neurons demonstrate its progressive accumulation, while cell transport and metabolism are violated, which contributes to the death of neurons and activation of glia. The results showed that age-related accumulation of lipofuscin was observed in all studied regions of the hippocampus during aging in animals on a standard diet. However, no such accumulation of lipofuscin was found in the granular neurons of the dentate fascia of the hippocampus in animals on a high-fat diet. The data obtained, in particular, the reduced lipofuscin content in the granular cells of the dentate gyrus during a prolonged high-fat diet, suggest that such a diet may activate compensatory or adaptive mechanisms in the hippocampus that prevent cellular aging.

Mitochondria form a dynamic network within the cell, the morphology of which is determined by the balance of fusion and fission processes and is widely used as a phenotypic indicator of cell state. However, qualitative classes and one-dimensional morphometric indices poorly discern the global organization of the network and can combine topologically different states under the general label of “fragmentation.” In this paper, the authors propose a phase-based approach to describing mitochondrial morphology in terms of steady-state states of a dynamic graph and map connectivity regimes in a minimalistic stochastic model of edge rearrangements under fixed contact geometry. Network states were analyzed in the space of complementary topological parameters, including the fraction of vertices in the largest connectivity component C = S₁/N, the number of components N_c, the average degree ⟨k⟩, and the cyclomatic number β₁. It is shown that the fragmentation phenotype is not a unique morphological state and is characterized by pronounced structural heterogeneity, detectable only in a multidimensional topological description. Scanning the pfus control parameter revealed a transitional region of connectivity reorganization, localized by the maxima of Var(C) and percolation susceptibility x, reflecting increased component structure fluctuations in the final system. The proposed framework provides a foundation for a more rigorous interpretation of morphological phenotypes as a state space and for further comparison of microscopic data with models of mitochondrial network dynamics.