Biophysics最新文献

A bioluminescence enzymatic assay of saliva was proposed as a noninvasive method to monitor the functional state of the body. The luminescence intensity from coupled enzymatic reactions catalyzed by NADH:FMN oxidoreductase and luciferase on exposure to saliva served as an indicator of the body state of workers at work. The absence of a significant difference between bioluminescence values measured before and after a shift with no changes in biochemical, physical, and chemical parameters of saliva suggested adaptation to a workload. An increased bioluminescence intensity was typical for workers in a state of chronic fatigue; a decreased intensity was observed in workers with chronic diseases and harmful habits. Bioluminescence intensity was found to depend on the concentrations of lactate and lipid peroxidation products, the ionic and mineral composition, and parameters of free radical oxidation and antiradical protection. Thus, the dependence of the saliva constituents on the life conditions and health status of workers can be detected using the bioluminescence enzymatic bioassay, which is suitable for rapid occupational monitoring.

Developing remote and proximal sensing techniques to detect the early photosynthetic responses in stress conditions is of importance for agriculture and ecology. The photochemical reflectance index (PRI), which is typically calculated from the reflected light intensities at 531 and 570 nm, is potentially sensitive to rapid changes in photosynthesis under unfavorable conditions. Mechanisms of changes in PRI are thought to include chloroplast shrinkage, aggregation of light-harvesting complexes, transitions in the xanthophyll cycle, and changes in chlorophyll and carotenoid concentrations. This renders it difficult to employ PRI difficult in monitoring plant health. Use of pulsed light for measurements, study of the light-induced changes in PRI, and analysis of modified PRIs provide means to improve the efficiency of PRI applications. Other means (e.g., developing methods to estimate PRI on the basis of RGB imaging) are also impossible to exclude. Improving techniques to measure and analyze PRI holds significant promise for monitoring the photosynthetic responses of plants to environmental stress factors.

The kinetics of delayed fluorescence and phosphorescence of the photosensitizer erythrosine in fragments of normal tissues and malignant tumors of breast of the oncological dispensary patients was studied in vitro. It was shown that the kinetics of delayed fluorescence of the dye was formed as a superposition of signals of thermally activated luminescence and glowing resulting from singlet-triplet annihilation of photosensitizer molecules and singlet oxygen. Quenching of the annihilation component of delayed fluorescence was detected when molecules were excited by a series of pulses with a frequency of 5–10 Hz. The shape of the delayed fluorescence curve and the intensity and duration of the afterglow of dye molecules were determined by the ratio of the rates of oxygen consumption/restoration in tissues. The correlation of delayed fluorescence indices with the clinical and morphological characteristics of tumors has been established; the application of the results in optical express diagnostics of tissues is discussed.

Plastoquinone (PQ) is a mobile electron carrier from photosystem II to the cytochrome b₆/f complex in the photosynthetic electron transport chain (PETC). In addition, PQ acts together with many other isoprenoids to perform the antioxidant function and to protect plant cells from reactive oxygen species (ROS). The review describes the PQ reactions with ROS, including singlet oxygen, superoxide anion radical, and hydrogen peroxide, in chloroplasts of higher plants. Data from many studies on the effect of various stress factors on PQ biosynthesis were analyzed to demonstrate that the PQ content increases in almost all stress conditions. An increase in PQ biosynthesis is therefore a factor that contributes to the plant viability by protecting the photosynthetic apparatus from oxidative degradation. A special section describes the methods to create plants with a higher PQ level and to assess their resistance to environmental factors. Applications of plant PQ as a protector of membrane structures from oxidation are discussed on the basis of its high antioxidant activity and the capability of diffusing in the lipid phase.

The results of studies of the luminescent culture system of Mycena gombakensis fungus isolated from wood samples are presented. The changes that occurred during 10 years of storage of samples in nonsterile conditions and the dynamics of luminescent signals are described. The identification of the fungus species was performed by phylogenetic analysis. A number of unique features of M. gombakensis are presented, expanding the understanding of the nature of luminescent fungi. The data we obtained open the prospects of using M. gombakensis both in biotechnology and in the study of the biophysics of a complex system of basidiomycetes.

The effect of cationic antiseptics (at micromolar concentrations) on PSII active core complexes isolated from spinach plants with an intact water oxidation complex and on PSI core complexes from cyanobacterium Synechocystis sp. PCC6803 were studied. Of the antiseptics studied (miramistin, chlorhexidine, octenidine, and picloxydine), octenidine had the greatest effect. It was concluded that its effect on PSII consisted primarily in affecting the structure of the light-harvesting antenna (CP43 and CP47), through which the excitation energy is delivered to the reaction center. As a result, the chlorophyll molecules in this structure were destabilized and their optical and functional characteristics changed. Similar effects were also observed in cyanobacterial complexes of PSI. In addition, the antiseptic affected the rate of establishment of the equilibrium distribution of excited states by spectral forms in the PSI antenna complex. A significant effect of octenidine on the electron transfer rate in the PS I complex was also found: in its presence, the recombination of photo-separated charges between the photoactive pigment P700 and the terminal acceptor F_A/F_B occurred twice as fast.

The study of low-dose effects is relevant in connection with the expansion of areas with anthropogenic load. Thorium is one of the background-forming elements in natural ecosystems, its content can increase in the environment during the extraction of natural resources and the operation of thermal power plants. Of particular interest are the bioeffects of thorium in the presence of humic substances, natural detoxifiers. The aim of this study was to evaluate the neutralizing effect of humic substances under conditions of low-dose exposure to thorium-232 (<0.04 Gy). A bioluminescent system of enzymatic reactions, including bacterial luciferase and NAD(P)H:FMN-oxidoreductase, was used as a model biological object. Activation of bioluminescence at the initial stage of thorium-232 exposure (up to 50 min) and an increase in the content of reactive oxygen species after 50 min of exposure were observed. The relationship between the intensity of bioluminescence and the content of reactive oxygen species (correlation coefficient of –0.86) was shown. The presence of humic substances neutralized the activating effect of thorium and reduced the content of reactive oxygen species to a control level. The effect of humic substances on the rate of the NADH-dependent enzymatic redox process has been demonstrated. The results we obtained contribute to the understanding of the molecular mechanisms of thorium-232 exposure and the neutralization of its effect on enzymatic processes.

The mechanisms of acclimation of primary photosynthetic reactions in the green microalgae Chlamydomonas reinhardtii to the toxic action of cadmium were investigated by analyzing the dynamics of the distribution of key photosynthetic parameters in the cell population. A synchronous culture of microalgae was incubated for 96 h in the presence of 25 μM Cd, and OJIP-transient curves of individual cells were recorded at different stages of incubation with the toxicant using an original microfluorometer. The analysis of OJIP-transient curves made it possible to determine distributions of key JIP-test parameters: F_V/F_M, ET_O/ABS, RC/ABS, which represent photochemical activity of PS II, electron transport in PS II, and light absorption per active reaction center in PS II, respectively. Acclimation of primary photosynthetic reactions in microalgae to cadmium was accompanied by the appearance of two dominating cell fractions, which demonstrated the stable values of photosynthetic parameters when energy imbalance occurred due to the presence of the toxicant. The cells related to the first fraction retained moderate PS II activity by the effect of reduced PS II antenna size, while the cells of the second fraction showed low photochemical activity of PS II keeping antenna size similar to that of the control cells.

Abstract—The saliva of athletes with anaerobic (track and field athletes) and aerobic (swimmers) physical loads was studied. Saliva was collected before (in a state of physical rest) and after training. It was found that physical load significantly increased the concentration of total protein in saliva and the activity of hydrogen ions (pH) in the saliva. Catalase activity in saliva was significantly increased only after aerobic physical load, as opposed to anaerobic load. The bioluminescent saliva index was significantly increased for athletes engaged in aerobic physical load compared to that for an anaerobic load. Saliva biomarkers such as the concentration of lactate and total protein, catalase activity, concentration of calcium, potassium, and magnesium ions, as well as the content of group IV amides, had a significant effect on the enhancement of light emission in a bioluminescent two-enzyme reaction. The content of group IV amides and a complex of oligosaccharides, polysaccharides, phosphatase, and phospholipids in the saliva of athletes engaged in anaerobic physical load could more strongly inhibit bioluminescent glow than the concentration of triene conjugates and the content of group II amides in the saliva of athletes engaged in aerobic physical load. Thus, significant biomarkers of the physiological state of the body have been identified in the saliva of athletes engaged in aerobic or anaerobic physical loads, which were able to affect the integral response of a bioluminescent enzymatic biotest. A change in the integral bioluminescent saliva index, depending on the type of physical load for an athlete, can be used in sports medicine to prevent physical overloads.

Photobiology is rapidly developing field of basic and applied research. The Russian Society for Photobiology (RSP) promotes creative activity and communication of researchers and practitioners in photobiology and related disciplines. The X Congress of the RSP took place in September 2023. The article provides definitions of photobiology, biophotonics, photobiotechnology, and bioluminescence. The history of the RSP is described in brief. The program and results of the X Congress are reviewed, including a summary of articles that are based on reports at the Congress and are the closest to biophysics.