Vol 63, No 5 (2018)

Abstract—A study of redox reaction kinetics in chromium-containing fixatives (mixtures of chromic acid, bichromate, formaldehyde, and acetic acid) showed that these fixatives were unstable chemical mixtures characterized by rapid kinetics of redox processes. Therefore, biological material fixation occurs in a non-stationary solution of a variable composition, including chromic acid, bichromates (chromium(VI)), formaldehyde, acetic acid, formic acid, and chromium(III) acetate. We propose the division of chemical fixation in these fixatives into two successive stages (“two-step fixation protocol”): the tissue is fixed in an acetic acid–formaldehyde mixture (a rapidly penetrating fixing mixture) at the first stage and washed thoroughly, and treated by the mordant for the staining at the second stage. Such a protocol will at least preserve the original composition of chromium-containing fixatives.

Abstract—The entropic effects for the energy landscapes of macromolecules are considered. We use the ideas and methods of multidimensional geometry and topology, expansion into a multidimensional Fourier series for a potential-energy surface, and the Gaussian distribution function for the expansion coefficients to describe the interaction between conformational degrees of freedom to investigate the free energy surface in the space of dihedral (torsion) angles. We show that the free-energy surface for a macromolecule that forms a unique 3D structure in the framework of the proposed approach has the following features. The main properties of the free-energy surface can be represented in terms of a two-dimensional surface, which depends on two generalized variables. At low temperatures, the multidimensional space of torsion angles can be divided into region that belongs to the deepest central energy funnel and the region of satellite funnels. The funnels are separated by relatively high energy barriers, whose height decreases as the representative point moves up further away from the bottom of the funnel. The depths of satellite funnels decrease while the distances from the central funnel becomes larger. The funnels are surrounded by smooth entropic barriers. The height of entropic barrier is at a minimum for the central funnel, while the entropic barriers heights of satellite funnels increase as funnels move further away from the central funnel. As the temperature increases, the satellite funnels are destroyed, starting from the most distant central one. When the temperature is higher than the critical point (proportional to the specific gain in the potential energy during the formation of a unique 3D structure) the compact state becomes unstable and the global minimum of free energy disappears. As the number of interacting torsion angles (the length of the polymer chain) increases, the critical temperature becomes higher.

Abstract—The formation of long-lived reactive species of gelatin, casein, and casein hydrolysate with a half-life of approximately 4 h in protein solutions subjected to moderate hyperthermia has been demonstrated by chemiluminescence analysis. The long-lived reactive species of these proteins and casein hydrolysate were found to cause prolonged generation of H₂O₂, and the mechanism underlying this process was considered. The body temperature elevation observed in warm-blooded organisms in various diseases is presumably accompanied by the formation of long-lived reactive species of various proteins; the generation of reactive oxygen species by these proteins may be one of the protective cellular mechanisms that contribute to elimination of diseases.

Abstract—Using optical and Fourier transform infrared (FTIR) difference spectroscopy, microwave radiation was found to affect the bacteriorhodopsin (BR) structure in films at a 30% relative humidity. This study is the first to demonstrate that a transition from the dark-adapted basal state BR₅₆₀ to a state similar to the light-adapted state BR₅₆₈, which is a mixture of BR₅₆₈ and other isomeric forms, occurs in the absence of external photoexcitation on exposure to microwave radiation with a frequency range of 8 ≤ f ≤ 18 GHz and an intensity lower than 10 mW/cm². The initial response of dark-adapted BR to microwave radiation included collective motion of a large portion of protein atoms, producing relatively strong signals in the regions 3700–3300, 2400–2300, and 800–600 cm^–1 of the FTIR difference spectrum. Relatively weak amplitude responses were detected in the frequency range characteristics of the retinal chromophore and amide bands (Amide I and Amide II). The effects reflected changes in the retinal chromophore structure and local changes in the chromophore microenvironment.

Abstract—The absorption spectra of lysed and non-lysed erythrocyte samples isolated from chicken, goose, and guinea pig blood were studied. It was found that the position of the maxima of Soret bands for lysed erythrocyte samples from the chicken and goose blood shifted into the short-wave region of the spectrum compared to the original samples. No band shift was observed for the guinea pig erythrocytes. When interpreting the short-wavelength shift of the Soret band, the following factors that may lead to this effect were considered: a physical factor (variation in the angle of the spectral slope of absorption background, the presence of a nucleus in the erythrocyte and a change in relative permittivity) and a chemical factor (the possibility of methemoglobin and hemichrome formation). It has been shown that the contribution of these factors to the short-wavelength shift is small and therefore it is possible to ignore these factors when interpreting the Soret band shift. To explain the observed effect, we have developed a hypothesis according to which a short-wavelength shift occurs due to the formation of free molecules of oxyhemoglobin in the dissociation of the oxyhemoglobin–inner erythrocyte membrane surface complex. Using this hypothesis, differences in the positions of Soret band maxima for different animals are explained consistently.

Abstract—We report a new microfluidic biosensor to detect changes in the transcriptional activity of the single genetically modified cells of the Helicobacter pylori bacterium in response to exogenous factors. A microfluidic chip was used as the basis for the development of the biosensor, in which the channel wall surface was modified to provide effective cell immobilization and maintenance of cell viability. In order to demonstrate the efficiency of the biosensor, the changes in the fluorescence of the GFP protein, the gene of which was under the control of the pH-dependent virulence genes of H. pylori, in response to acidic stress, were registered. The developed microfluidic biosensor may be used not only for the basic microbiological research, but also for the diagnostics of different pathological states.

Abstract—Among the most hopeful biomaterials, metallic nanoparticles with antibacterial and anticancer properties are expected to open new avenues to fight and prevent various cancer and infectious diseases. The aim of the current study was the biosynthesis of plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone-AgNPs (P-AgNPs) using the endophytic fungus Fusarium solani isolated from an endangered medicinal plant Plumbago rosea. The fungus was identified according to its morphological characteristics and nuclear ribosomal DNA ITS sequence analysis. The synthesized P-AgNPs were initially noticed through visual color change from yellow to reddish brown and further confirmed by surface plasmonic resonance (SPR) band at 450 nm using UV-visible spectroscopy. Fourier transform infrared (FTIR) analysis showed amines and amides that are responsible for the stabilization of P-AgNPs. High-resolution scanning electron microscopy (HRSEM) showed that P-AgNPs were well dispersed, spherical, and well within the range of 23.2, 33.2 and 33.7 nm. X-ray diffraction (XRD) study revealed crystalline nature of P-AgNPs. These P-AgNPs displayed good antibacterial activity in dose dependant manner. The synthesized P-AgNPs exhibited dose-depended cytotoxicity against MCF-7 human breast cancer cells, the inhibitory IC₅₀ were found to be 14.5 μg/mL. These nanoparticles were further studied for their anticancer activity and showed high selective toxicity against the MCF-7 breast cancer cell line. The anticancer activity also executed through inhibiting the cells at the phase DNA synthesis.

Abstract—Soil organic matter of forest ecosystems is characterized by high sensitivity to increased temperatures, which makes soil organic matter more vulnerable under the conditions of global warming. In this study, evaluation of the effects of different components of woody litter (leaves and small branches of aspen) on the dynamics of the activity and quantitative characteristics of microbial communities of soils under the conditions simulating climate warming was carried out. In our experiment we used samples of gray forest soil from the forest biocenosis of the Moscow area, which is typical of the European part of Russia. Incubation of soil samples to which crushed leaves and branches were added (0.5 wt %) was carried out at constant temperatures of 5, 15, and 25°C for 28 days. The dynamics of CO₂ emission, organic carbon content, microbial biomass, as well as the number of the ribosomal genes of bacteria, archaea, and micromycetes, were evaluated. The optimal temperature for plant litter decomposition was 15°C; a decrease or increase in the temperature resulted in a decrease in the intensity of the litter decomposition process. Addition of plant residues in the temperature range of 5–15°C resulted in a significant increase in the temperature sensitivity of the soil-respiration process and the temperature coefficient increased from 1.75 to 3.44–3.54. In the temperature range of 15–25°C an inverse correlation was observed. At high temperatures addition of plant residues stimulated decomposition of soil organic matter. These results contribute to the understanding of the dynamics of soil carbon and can be used in predictive models of the processes of plant-litter decomposition and the dynamics of soil organic matter in forest biocenoses in Eurasia under the conditions of climate change.

Abstract—The effect of 40%-glucose solution and 60%-glycerol solution on the weight and geometric parameters of the myocardium was studied in vitro in order to improve the accuracy of estimating the glucose and glycerol diffusion coefficients in the myocardium by including changes in the geometry and water content of a tissue sample in a mathematical algorithm. The temporal kinetics of the weight, thickness, area, and volume were measured using porcine myocardium samples during their immersion in 60%-glycerol solution or 40%-glucose solution in vitro. All parameters started to decrease immediately after placing myocardium samples in immersion agents (tissue shrinkage). The weight and geometric parameters of the sample then increased gradually (tissue swelling), leading to tissue saturation in almost all cases. By approximating the temporal kinetics, the degree of dehydration and the characteristic times of transverse and longitudinal shrinkage and swelling of the myocardium were determined. More significant and rapid dehydration of myocardial tissue was observed case of using 60%-glycerol solution, while a stronger and faster swelling of the myocardium was observed when 40%-glucose solution was applied.

Abstract—Changes in the fatty acid levels in the cardiac and gastrocnemius muscles of rats that were chronically alcoholized for 3 and 6 months were studied using two methods of alcoholization: 30% ethanol-containing agar (method I) and a 5% ethanol-containing liquid diet with a balanced nutritional status (method II). In the control group, the fatty acid level in the cardiac muscle was considerably higher than that in the gastrocnemius muscle. In the animals that were alcoholized over a 3-month period using method I, a considerable increase in the levels of myristic, pentadecanoic, palmitic, stearic, and dihomo-γ-linolenic acids and the total amount of fatty acids and a decrease in ω-3 docosapentaenoic acid level were found in the cardiac muscle. After a 6-month period, during which rats were alcoholized using method I, an increase in the levels of palmitoleic and ω-6 docosapentaenoic acids and a decrease in the levels of stearic, eicosadienoic, and arachidonic acids were found. The amount of ω-3 docosapentaenoic acid in the myocardium, compared to that observed after a 3-month period during which rats were alcoholized, remained reduced compared to the control. In the gastrocnemius muscle of rats alcoholized for 3 months using method I, the amounts of myristic, vaccenic, dihomo-γ-linolenic, and ω-6 docosapentaenoic acid increased. Simultaneously, there was a tendency for the total amount of saturated, monounsaturated, and ω-6 polyunsaturated fatty acids and the total amount of fatty acids to rise. After a 6-month alcoholization, a decrease in the levels of myristic, oleic, linoleic, α- and γ-linolenic, and eicosadienoic acids, as well as the total amount of saturated, ω-6 polyunsaturated fatty acids and the total amount of all fatty acids was found. When animals were alcoholized over a 3-month period using method II, a significant increase in the amount of dihomo-γ-linolenic acid was detected in the cardiac and gastrocnemius muscles. The role of these changes in the muscle pathologies is discussed.

Abstract—The deuterium concentration in normal mice and mice inoculated with 4T1 mammary carcinoma has been studied by magnetic resonance imaging (MRI) and ¹H and ²H contrast. Mice received deuterium (up to 10%) in drinking water. The reversible effect was observed when mice began to drink ordinary drinking water. The average period that is required to perform hydrogen/deuterium exchange in all parts of the mouse is 2.4 days. Hydrogen/deuterium exchange rates in normal and deuterated mice are not reliably distinguished. The day range for hydrogen/deuterium exchange in biopolymers depends on its localization in the mouse and varies from 8 to 24 days. The nonmonotonic character of the time dependence of the deuterium level was observed after a weekly consumption of drinking water with an increased deuterium content in the tumor. The median survival rate of the inoculated mice that received drinking water with an increased content of deuterium was 4 days longer than that in the control group.

Abstract—The issue of how observation of a process in quantum mechanics may influence its outcome is described by case studies of quantum emission by a two-level system and the passage of a particle through a potential barrier. In the first case, the observation can reduce the probability of quantum emission by the two-level system (the quantum Zeno effect). In the second case, the observation of a particle can significantly increase the probability for a particle to pass through a barrier, sometimes even by many orders of magnitude (the barrier anti-Zeno effect). The possibility of such effects in biological systems is discussed.