Vol 61, No 4 (2016)

A numerical simulation of the folding of a model polymer chain of 50 units with valence bonds of a fixed length and fixed valence angle values has been performed using the strong friction approximation. The rate of energy dissipation in the system has been analyzed for conformational motions along a trajectory determined by the equations of mechanics and the trajectories characterized by random and variable deviations from the mechanical path. The validity of the principle of the minimum average rate of the energy dissipation for the conformational relaxation of a macromolecule in a viscous medium has been demonstrated. A profile of the relaxation energy funnel for the folding of a macromolecular chain has been constructed. Slow and rapid stages of folding could be distinguished in the energy funnel profile; the final state was separated from the nearest conformations of the folded chain by an energy gap.

The temperature dependence of the scattering intensity, average size, and size distribution for supramolecular particles in aqueous solutions of lipopolysaccharides from Azospirillum bacteria was investigated by dynamic light scattering. Relationships were obtained that made it possible to comparatively estimate the mass–volume concentration of the biopolymeric substance in suspensions and the number concentration of supramolecular particles with their size and degree of polydispersity taken into account. In the range from 0 to 60°C, two types of the temperature dependence of scattering intensity were found: (a) with an irregular spasmodic change in scattering intensity and with considerable heterogeneity of the systems with respect to particle size and (b) with a smoother character of this dependence with considerably decreased heterogeneity of the suspensions. In the ranges of the latter type, whose location depended on what strain was used to isolate lipopolysaccharides, it proved to be possible to correctly determine the parameters of the supramolecular particles (of the supposedly formed micellar phase) by dynamic light scattering. The revealed statistically significant differences in the size and the concentration of the micellar particles are explained by their dependence on the peculiarities of the chemical structure of lipopolysaccharides. Atomic-force microscopy was used for an independent morphological estimation of the preparations, yielding good agreement with the dynamic light-scattering results.

Reconstruction of the spatial structure of inulinase (EC 3.2.1.7) from Kluyveromyces marxianus (an enzyme that hydrolyzes inulin and other fructose-based polymers to fructose) was carried out by highthroughput computational modeling. A structural model of a closely related homologous protein, viz., invertase from yeast Saccharomyces cerevisiae (PDB-ID: 4EQV), was used as a template. The reconstructed model can be used for computer calculations for optimizing the biotechnological feasibility of inulinase.

This review summarizes the results of recent studies in which the role of selenium has been addressed by investigating the functions and biochemical properties of mammalian selenocysteine-containing proteins and their involvement in maintaining the normal function of the male reproductive system. Selenium is an essential trace element; its deficiency leads to serious diseases, including male infertility disorders, prostate cancer, testicular cancer, etc. A total of 25 selenocysteine-containing proteins are known now, and almost half of them occur in the testis, highlighting the significance of the issue.

NMR proton spectra were recorded in the range of proton resonance in the nucleotide aromatic ring of monomeric ATP–G-actin and the Mg²⁺–ATP–G-actin solutions in D2O to study the mechanism of ATP–G-actin hydrolysis and its role in F-actin formation in Mg²⁺-containing solutions. The experimental data show variations in the proton chemical shifts of the H2 and H8 peaks and splitting of the H8 resonance peak of G-actin-bound ATP adenine caused by interaction with magnesium dication. The observed variations in spectra are explained by hydrolysis of monomeric ATP–G-actin to ADP–G-actin, which is regarded as the initial stage of the G-actin to F-actin transformation.

The effects of temperature and the membrane-active protein CTII on the formation of nonbilayer structures in mitochondrial membranes were studied by ³¹P-NMR. An increase in ATP synthase activity was found for the first time to accompany the formation of nonbilayer packed phospholipids with immobilized molecular mobility in mitochondrial membranes. Computer modeling was additionally employed in studying the interaction of important phospholipids found in mitochondrial membranes with the molecular surface of CTII, which behaves like a dicyclohexylcarbodiimide-binding protein (DCCD-BP) of the F₀ group in a lipid phase. Proton permeability toroidal pores were assumed to form in mitochondrial membranes from nonbilayer-packed phospholipids immobilized via interactions with DCCD-BP. Proton transport along a concentration gradient through the transit toroidal permeability pores may induce conformational changes necessary for mediating the catalytic activity of ATP synthase in the subunits of the F₀–F₁ complex.

Light green pigment mutants with a reduced chlorophyll b content were constructed in the microalga Chlamydomonas reinhardtii Dangeard. A simultaneous recording of the induction curves for prompt and delayed fluorescence and the redox state of P700 in the microsecond range with a M-PEA-2 fluorometer revealed decreases in the quantum yield of electron transport in PS2 (φE₀) and the performance index (PI_ABS) and increases in the quantum efficiency of energy dissipation (φD₀) and ΔpH-dependent nonphotochemical quenching (qE and NPQ). The light-dependence curves of the fluorescence parameters confirmed a decrease in the coefficient of maximum utilization of light energy (α) for the mutants. However, the mutants showed an adequate rate of electron transport at a medium light intensity under steady-state conditions. The mutations did not directly affect the oxidation reactions of the PS1 pigment (P700) and the decrease in delayed fluorescence. Experience in using the mutants to test polluted waters of Kazakhstan confirmed that the mutants are promising for use in biomonitoring for mutagens.

The high-amplitude swelling of mitochondria is critically considered. In contrast to numerous statements by some authors about a marked swelling of isolated liver mitochondria under the influence of palmitic acid, calcium ions, or hypotension, we have shown that mitochondria are generally not subject to highamplitude swelling. According to optical-microscopy data even during long-lasting incubation (in distilled water) where full hypotension takes place, the size of liver mitochondria (approximately 1 µm) can be enlarged by no more than by 40%. Under short-lasting hypotension or the addition of palmitic acid the mitochondrial diameter becomes greater by only 20% or remains virtually unchanged. The light scattering of the mitochondrial suspension measured using a photometer according to the decrease in optical density declines by 2.5 times. A decrease in the light scattering in hypotension or via the addition of palmitic acid or calcium (in an isotonic medium) occurs because of damage (even destruction) to the outer membrane, rather than due to the swelling of mitochondria, as was previously believed. The inner membrane is not significantly expanded. The destruction of the outer membrane reduces the probability of light scattering by each mitochondrion at the boundary layer of the water/membrane interface. Release of substances from the matrix resulting in a decrease of its refractive index may additionally contribute to the decrease in light scattering. Palmitic acid and calcium (at concentrations of 10 to 100 µM) cause permeabilization and disruption of the outer membrane gradually, over several minutes. Full hypotension activates this process very rapidly, viz., within a fraction of a second. Under low ionic-strength conditions, the addition of calcium leads to neutralization of negative charges on the membrane surface, which induces aggregation of mitochondria, thus enhancing light scattering and creating the illusion of mitochondrial swelling.

An electrophoretic assay of lactate dehydrogenase (EC 1.1.1.27) isozymes in the tissue homogenates of cardiac and skeletal muscles, kidney, lungs, spleen, and liver of the raccoon dog Nyctereutes procyonoides from two different geographic zones, viz., northwestern Russia and Poland, as well as the Arctic blue fox Alopex lagopus L. and the red fox Vulpes vulpes L. was performed during the preparatory period to the winter season. Raccoon dogs, which hibernate under natural conditions, differ from other canids (the red fox and Arctic blue fox) to which they are close taxonomically by their body weight and by the higher proportion of aerobic H subunits of lactate dehydrogenase in all organs except for the heart. A higher content of “fast” anode fractions, lactate dehydrogenase-1 and lactate dehydrogenase-2, in the heart, kidney, lungs, liver, and spleen was detected in the raccoon dogs from the northern region compared to those from the southern geographic zone. The shift in the reaction catalyzed by lactate dehydrogenase towards the production of pyruvate indicates that this metabolite is necessary for the synthesis of fatty acids during lipogenesis in the autumn.

This paper presents the results of the study of oxidative metabolism of the blood of intact animals subjected to prolonged exposure to nitric oxide at concentrations of 20, 50, and 100 ppm. The experiment was carried out with Wistar rats. NO inhalation was performed for 30 days. The state of blood oxidative metabolism was evaluated after inhalation and a 30-day-long recovery period after discontinuation of NO oxidative stress. The intensity of lipid peroxidation was studied in plasma and erythrocytes by induced biochemiluminescence and the measurement of the level of malondialdehyde. The activity of superoxide dismutase was determined in the hemolysate of erythrocytes. It was established that the optimal dose of inhaled NO is 20 ppm: a maximum increase in the total antioxidant activity after 30 days and normalization of lipid peroxidation in the blood after the completion of the recovery period were observed at this concentration. High concentrations of nitric oxide (50 and 100 ppm) initiated lipid peroxidation in erythrocytes and plasma after discontinuation of NO oxidative stress (after the completion of the recovery period) thus enhancing catalytic properties of superoxide dismutase.

Simple models that describe some features of the electrical brain activity in rats with genetic absence epilepsy recorded before and after an epileptic seizure have been proposed in this study. These models can help to analyze the efficiency of the Granger causality analysis of the directional connectivity determination. The comparison of the results of the experimental and modeled signal analysis, on one hand, reveals a number of artifacts of this method, and on the other hand, proves its effectiveness in the research on absence epilepsy mechanisms.

The role of p38 mitogen-activated protein kinase in regulating the cell responses to ultralow-intensity centimeter microwaves (8.15–18.0 GHz, 1 µW/cm², 1 h) was studied in male BalbC mice. Mice were tested for the level of protein phosphorylation in the NF-κB (p65 and IKK), JNK, and IRF3 signaling cascades expression of TLR4 and stress-inducible heat shock proteins Hsp72 and Hsp90 in splenic lymphocytes and pro- and anti-inflammatory cytokines and IL-10 in the blood serum. An inhibitor of the p38 signaling pathway (p38 inhibitor XI) was shown to reduce the sensitivity to ultralow-intensity ultrahigh-frequency electromagnetic radiation. This was evident from a decrease in radiation-induced activation of the NF-κB signaling pathway, expression of Hsp72 and Hsp90 in splenic cells, and an accumulation of proinflammatory cytokines (IL-6, IL-17, TNF-α, and IFN-γ) in the blood serum of irradiated mice pretreated with p38 inhibitor XI. However, p38 inhibitor XI did not attenuate the activation of the p38 and IRF3 signaling pathways and overexpression of TLR4 in splenic cells of irradiated mice. It was assumed that p38 mitogenactivated protein kinase is involved in regulating the nonspecific defense responses does not determine the murine sensitivity to ultralow-intensity electromagnetic waves of the centimeter range.

The literature data on implant materials for recovering from osseous injuries and defects were reviewed. Hydroxyapatite and bioactive glass are the leading artificial implant materials. Chitosan, polylactide, adgelon, and salicylic acid have found application in this area as biocompatible surgical materials that also promote wound healing and regeneration. When using hydroxyapatite as an implant material, its active groups, such as phosphate, hydroxyl, and others provide contacts; cell migration and adhesion on the matrix surface, formation of an intermediate layer of osteoid type, and fusion of bone and implant then occur. In the case of bioactive glass, the silanol groups are involved in bond formation. The study of mechanisms of bond formation between biological tissue and implant material and search for new biocompatible materials are important tasks of medical research in the field of implantation and post-traumatic regeneration.