Biophysics最新文献

The results of a comparative study of electron transport in chloroplasts in situ in the leaves of shade-tolerant and light-loving tradescantia species (T. fluminensis and T. sillamontana) grown under conditions of strong (800−1000 μmole m^–2 s^–1of photons) or weak (moderate) illumination (50−125 μmole m^–2 s^–1of photons) are described. Electron transport processes were monitored using the methods of electron paramagnetic resonance and optical spectroscopy. The photoinduced redox transformations of the primary electron donor of photosystem I (P₇₀₀) and the slow induction of chlorophyll a fluorescence were studied. It has been shown that plants acclimated to high light intensity are characterized by faster processes of P₇₀₀ oxidation and chlorophyll a fluorescence attenuation compared to plants grown at low light intensity. The data obtained are analyzed in the context of “short-term” mechanisms of pH-dependent regulation of electron transport in intact chloroplasts (non-photochemical quenching of excitation in photosystem II, slowing down the oxidation of plastoquinol by cytochrome b₆f complex, and activation of Calvin−Benson cycle reactions).

The latest research on the use of gold nanoparticles obtained by an environmentally friendly method of “green” synthesis is considered. These nanoparticles are obtained with extracts from leaves, bark and seeds of plants of medicinal value, which are combined with gold nanoparticles or other types of nanoparticles. The data referenced in this review are taken from reputable platforms, including Google Scholar, ResearchGate, PubMed, and Scopus. We will show the results of studies that have demonstrated the effects of nanoparticles on tissues. Numerous studies indicate that the toxicity of gold nanoparticles obtained using environmentally friendly methods is minimal. To reduce the impact on the environment, priority should be given to the development of environmentally friendly methods for the synthesis of nanomaterials. In this regard, researchers are looking for “green” methods to close the gaps and reduce possible problems. Biological synthesis processes are economically efficient, non-toxic, relatively uncomplicated, and environmentally friendly. The process of “green” synthesis involves the production of biological compounds from extracts of plants, bacteria and algae. The ability to manipulate the morphological characteristics (such as size, shape, and crystal structure) of gold nanoparticles during their creation plays an important role in a number of fields where nanoparticles are used. Biological molecules derived from plants are suitable for the production of metal nanoparticles. Numerous studies have demonstrated the possibility of using nanoparticles of both gold and other materials to perform therapeutic procedures with minimal impact on healthy tissues. In addition, such nanoparticles have the ability to repair damaged tissues.

Using alkaline gel electrophoresis of single cells of the spleen of male ICR (CD-1) mice exposed to five daily exposures to X-ray radiation at a dose of 1.4 Gy, DNA damage was studied on the day of the last irradiation against application of riboxin, or inosine (200 µg/g), copper chlorophyllin (20 µg/g), indralin (50 µg/g), and antioxidants: glutathione (350 µg/g) and ascorbic acid (150 µg/g) together. The 30-day survival of groups of ten mice was evaluated in parallel. The level of DNA damage when using indralin and riboxin did not differ significantly from the intact mice. However, one mouse each from the riboxin and antioxidant groups died. There were no deaths of mice from other groups, including the irradiated control. The use of antioxidants protected DNA to a small extent. Copper chlorophyllin did not protect DNA compared to the irradiated controls.

Among plant proteases, cysteine papain-like endopeptidases such as ficin, bromelain, and papain occupy an important place due to their high proteolytic activity in the physiological pH range of the medium. The processes of thermal aggregation and autolysis of protease molecules can have a significant influence on their activity and, consequently, on the prospects of practical application. The mechanisms of aggregation of protein molecules are still insufficiently studied and it is still impossible to unambiguously predict their aggregation stability on the basis of their amino-acid sequence. In this connection, the aim of this work was to study the processes of thermal aggregation and autolysis of molecules of some cysteine proteases. It was found that despite the similar structural and functional properties of ficin, bromelain, and papain their thermal aggregation processes proceed with different intensities. In particular, ficin and bromelain are approximately comparable in terms of their aggregation stability, whereas papain is significantly less susceptible to aggregation processes when exposed to elevated temperatures. It is suggested that the presence and configuration of internal structures of the molecule, such as cavities, tunnels, and pores, as well as the charge properties of its surface, have a significant influence on the stability of these cysteine proteases to aggregation processes.

Using the developed method of optical laser tomography, the possibility of recording and analyzing the three-dimensional distribution of subcellular organelles in eukaryotic algae (C. rainhardtii) was proved. The method allows one to analyze the redistribution of subcellular organelles (the nucleus and chloroplast) in consecutive slices of one cell in the norm and under the influence of modifiers of its functional state. According to the authors, the proposed approach will allow one not only to study the dynamics of the distribution of intracellular structures (nucleus, thylakoids, mitochondria, etc.), but also changes of a single structure during cell functioning.

The spin-chemical mechanism of radical pairs is considered today as the most probable molecular mechanism explaining the observed biological effects of weak magnetic fields. The magnitude of these effects depends on the spin relaxation rate, but no explicit functional dependence has been proposed. In this paper, an analytical solution of the Liouville–Neumann equation for a system of two electrons and a nucleus is found, taking into account spin relaxation and chemical kinetics. A relationship is obtained that relates the magnitude of the magnetic effect to the rate of relaxation due to thermal disturbances. The effect obeys a general quantum constraint. At plausible relaxation rates, the calculated effects are small and cannot explain the observations. It can be concluded that today, despite the attractiveness of the radical pair mechanism and the increased theoretical understanding, the problem of magnetobiology still does not have a conceptual solution free from contradictions.

Using Raman spectroscopy, fluorescence spectroscopy, and time-correlated photon counting, it was found that an increase in the temperature of the human erythrocyte incubation medium causes an increase in the homogeneity of hemoglobin distribution in the cytoplasm of erythrocytes and a decrease in the packing density of the globin molecule, which is most likely the result of the effect of “macromolecular crowding” of the cell. The revealed conformational changes are characteristic only of hemoglobin in the cell and do not depend on changes in the surface potential of the plasma membrane. It is assumed that there are several pools of hemoglobin molecules that differ in the structure and dynamics of the protein globule, forming a heterogeneous distribution of hemoglobin inside the erythrocyte due to the combining of hemoglobin molecules into clusters. The possibility of the involvement of these effects in the signaling and regulatory function of oxygen transport and transport is discussed.

The problem of purinergic regulation in synapses of phasic and tonic muscles of warm-blooded animals has been investigated. For this purpose, the effect of the cotransmitter of the main mediator, ATP, and its persistent metabolite, adenosine, on the contraction of various oculomotor systems of the rat, the lateral rectus (tonic) and circular (phasic) muscles of the eye, has been evaluated. ATP potentiated the carbacholine-evoked contraction of the rat lateral rectus muscle by one-quarter, while this purine, on the contrary, significantly inhibited the carbacholine-evoked contraction of the circular eye muscle. No significant manifestation of the modulatory effect of adenosine on the carbacholine-evoked contraction of the muscles under study was revealed. These results indicate a multidirectional postsynaptic effect of ATP on phasic and tonic oculomotor systems.

UV irradiation at doses of 3020, 4510, and 6040 J/m² was found to decrease the level of specific activity of free trypsin by 28, 32, and 49%, respectively. Adsorption immobilization on the matrix of chitosans with molecular weights of 200 and 350 kDa, entrapment in chitosan (<100 kDa) and chitosan succinate gel contribute to the preservation of trypsin molecule activity at the level of ~90% and higher. Under UV irradiation in the dose range of up to 6040 J/m² in the presence of a photosensitizer, methylene blue, at a concentration of 10^–4 mol/L the activity of free trypsin decreased by 72%. After immobilization, the stability of the enzyme complex under the above conditions increased: the activity of trypsin immobilized on the matrix of chitosans with molecular weights of 200 and 300 kDa was maintained at the level of about 75%, after entrapment of the enzyme in the chitosan gel (<100 kDa), by up to ~50%, and chitosan succinate, by up to ~70%. The molecular docking method revealed that a number of tryptophan, tyrosine, and phenylalanine residues, as well as two cystines, take part in the formation of bonds and interactions between the trypsin molecule and the matrices of chitosan and chitosan succinate, which probably determines the photoprotective properties of these polysaccharides. IR spectroscopy showed that after UV irradiation in the presence of methylene blue and without it, no significant changes in the wave number values in the region of the amide I, II, and III bands were detected in the spectra of trypsin immobilized on chitosan and chitosan succinate matrices, which indicates that the stability of the enzyme structure in the complexes with these polysaccharides is maintained.

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.