Biophysics最新文献

Photosystem II is one of the main pigment–protein complexes of photosynthesis, which is highly sensitive to adverse environmental factors. The heterogeneity of photosystem II properties is necessary for the resistance of autotrophic organisms to stress factors. The assessment of photosystem II heterogeneity can be used in environmental monitoring for the rapid detection of environmental pollution. A comprehensive approach to the assessment of photosystem II heterogeneity is proposed; it is based on a mathematical analysis of the shape of the chlorophyll a fluorescence induction curve of samples treated with 3-(3,4-dichlorophenyl)-1,1-dimethyl urea using a mathematical model and JIP test parameters. Fluorescence induction curves obtained for treated samples of Chlorella, Scenedesmus, Ankistrodesmus, Pleurochloris, and Stichococcus cell cultures were analyzed that grew in light with an intensity of 8 and 16 W/m^–2. For all cases, the ratio of reaction centers with different antenna sizes (alpha and beta centers) was estimated and the proportion of active and inactive oxygen-evolving complexes was determined.

The possibilities of using a test system based on live E. coli BL-21 (DE3) Codon Plus cells expressing pH-resistant Luciola mingrelica firefly luciferase to study the kinetics of the effect of aminoglycosides (using the example of gentamicin) on the content of ATP and luciferase inside and outside the cells were demonstrated. It has been shown that after 3 h of incubation of bacteria with an antibiotic it was possible to assess changes in cell viability and the effectiveness of the antibiotic, as well as to predict the formation of persisters. The method is promising for conducting rapid primary high-performance screening of antibacterial agents and drug forms to assess their effectiveness and the mechanism of action.

The aim of this study was to develop a combined technology of plasmon photothermal therapy and photodynamic therapy of transplanted cholangiocarcinoma PC-1 in rats. For photodynamic therapy, rats were intratumorally administered with indocyanine green diluted in polyethylene glycol at a ratio of 1 : 100 at a dose of 2 mg/kg. For plasmon photothermal therapy, gold nanorods diluted in polyethylene glycol (400 μg/mL) were intratumorally injected in a volume of 30% of the tumor volume. At 1 h after injection, the tumor was percutaneously irradiated with a diode infrared laser with a wavelength of 808 nm at a power density of 2.3 W/cm² for 15 min. The animals were removed from the experiment 72 h and 21 days after therapy. Morphological studies of the tumor were performed on sections stained with standard and immunohistochemical methods. A significant increase in tumor temperature was noted, up to 60.0 ± 4.1°C with combined plasmon photothermal and photodynamic therapy. After 72 h, pronounced necrotic changes were observed in the tumor tissue and intact tumor cells were observed only on the periphery of the tumor. At 21 days after therapy, a significant inhibition of tumor growth was noted; the inhibition index by tumor mass was 77.4%.

Measurements of the spectral composition of light at the boundary of the photic zone in seven coastal reservoirs, which are isolated from the sea to varying degrees, as well as in the marine water area and in a freshwater lake showed that in marine and brackish reservoirs, mainly green light reaches it; in lakes with a fresh upper layer it is orange, red and far-red. In meromictic reservoirs, the photic zone was limited by a colored layer of water with a massive development of phototrophic microorganisms. Their pigment composition is in good agreement with the spectral composition of transmitted light. The marine bays and lagoons were dominated by taxa with red pigments: cryptophytic algae with phycoerythrin-545, purple sulfur bacteria with okenone carotenoid, brown green sulfur bacteria with isorenieratene and bacteriochlorophyll e. In lakes with fresh upper water, unicellular algae and green sulfur bacteria with chlorobactene and bacteriochlorophyll d developed. The spectral range can serve as a selective factor that determines the composition of a community of phototrophs with structurally different antennas and similar light absorption spectra.

Improving the efficiency and precision of gene editing systems is of utmost importance for modern molecular biology and genetic engineering. Of particular interest is the design of controlled CRISPR/Cas9 systems, the activity of which could be regulated using various physicochemical stimuli, such as light irradiation, pH change, temperature, change of molecule concentration, and others. A promising direction in this area is the development of approaches to control activity at the level of guide RNA through photosensitive modifications to the structure and sequence of guide RNA, and additional oligonucleotides. This review focuses on the analysis of publications on design of photosensitive guide RNAs and their applications in gene editing systems using CRISPR.

The conversion of light energy in the near-infrared spectral range by photosynthetic pigment–protein complexes has been intensively studied in recent years in connection with the discovery of cyanobacteria, in the photosynthetic apparatus of which chlorophylls f and d absorbing long-wavelength light are present. Acaryochloris marina occupies a special place among such cyanobacteria. Its photosystem I contains mainly chlorophyll d; it is a part of a special P₇₄₀ pair, the absorption spectrum of which is shifted to the red region by 40 nm. This causes a decrease in the energy of the excited state of P₇₄₀ by ~0.1 eV compared with photosystem I containing chlorophyll a. Complexes of photosystem I from A. marina also have the following peculiarities: four chlorophyll a molecules of the reaction center are replaced by chlorophyll d, and the third pair of chlorophyll a molecules involved in electron transfer are replaced by pheophytin a. The presence of spectrally different cofactors (chlorophyll d and pheophytin a) made it possible to reliably establish the intermediates of primary charge separation reactions in this photosystem I. In this review, we considered the latest results of studies of photochemical energy conversion in the reaction centers of photosystem I of A. marina and possible mechanisms for compensating energy losses of the use of low-energy far-red light for photosynthesis.

It was found in vivo that the addition of caffeic acid and a low-molecular-weight bioluminescence activator that we have discovered to the mycelium of the luminous fungus Neonothopanus nambi led to a rapid and significant (by an order of magnitude and more) increase in the intensity of its light emission. It is proposed that the observed effect of activation of the fungus glow may be mediated by the oxidation of added substances by enzymes of the ligninolytic complex of basidiomycetes (in particular, peroxidases) with the emission of visible light quanta. Parallel in vivo experiments have shown that the addition of hispidin (a precursor of luciferin in luminous higher fungi) did not affect the intensity of light emission of the mycelium. In vitro studies have shown that caffeic acid and the discovered low-molecular-weight glow activator did not affect the light emission level of the enzyme luminescent system isolated from the mycelium of N. nambi in the presence of NADPH and significantly suppressed the luminescent reaction of the system induced by NADPH and hispidin. The totality of the data we obtained indicated the presence in luminous higher fungi of different biochemical pathways for the generation of visible light quanta involving different enzymes (or enzyme systems) and different substrates.

T4-related bacteriophage RB49 is capable of general plasmid transduction with a relatively high frequency. Due to this mechanism, bacteria can acquire the ability to adapt to changing environmental conditions and explore new ecological niches. The effects of pH, temperature, and irradiation with long-wavelength ultraviolet light (λ = 366 nm) on the characteristics of the phage RB49 preparation containing transducing particles with pTurboGFP-B plasmid DNA and virulent particles with their own DNA were studied. Data on changes in the titer of virulent particles and the frequency of transduction of the pTurboGFP-B plasmid by the RB49 phage were obtained. After exposure to UV radiation for 2 h, the frequency of transduction of the pTurboGFP-B plasmid by the RB49 phage increased by ~3 times. After storing the preparation in ice for 40 min, a several-fold increase in the transduction frequency was observed. Based on the experimental data we obtained, it was assumed that the transducing particles of the RB49 phage may be more resistant to long-wavelength UV radiation and temperatures close to 0°C than virulent ones and provide the transduction process more efficiently than under normal conditions. Similar processes can occur in well-lit reservoirs, including cold ones, in which phages related to RB49 may occur. This indicates the possibility of more intensive horizontal gene transfer in aquatic ecotopes than previously assumed.

Natural stress factors can lead to crop loss; when they act locally, stress signals spread, modifying the physiological state and increasing plant resistance. The purpose of this work was to study the effect of a combination of local factors on water metabolism under watering and drought. Wheat was grown in a greenhouse cabinet; drought was created by stopping watering. To assess the water metabolism, a modified index of stomatal conductivity measured by a thermal imager, the water conductivity of the leaf, and the relative water content in the leaves were used. It was found that the conductivity index decreased during drought and had a strong correlation with the hydration status of the plant (R > 0.7, p < 0.05). Under watering, the combined effect led to a decrease in the conductivity index compared to the condition without stimulation; the response decreased with increasing the distance from the stimulation zone. Soil drought reduced the amplitude of changes in the conductivity index. The local action of heating alone and illumination alone did not cause conductivity index changes. The results showed that the local effect of the combination of heating and illumination caused stress signals that reduced the water metabolism of wheat. Potentially, such signals might be of an electrical nature; however, the absence of changes in the conductivity index under drought and the effect of heating alone did not confirm this hypothesis.