Vol 62, No 1 (2017)

The principle of the minimum rate of energy dissipation for conformational movements in a viscous medium formulated in an earlier study (K.V. Shaitan, Biophysics, 2015, Vol. 60, p. 692) has been applied for a theoretical estimation of the distribution functions of the energy dissipation rates for selected elements of a macromolecule. Equipartition of energy dissipation rates among the nodes of the chain upon conformational movements in the statistical limit of the process is obtained. The uniform distribution of energy dissipation rates along the chain does affect on the formation of the collective conformational degrees of freedom and the folding dynamics.

The composition of plasma proteins adsorbed on the surface of perfluorocarbon emulsions stabilized by different triblock copolymers and their quantitative ratio were analyzed. The results allowed us to describe three types of protein adsorption on the surface of emulsion droplets. Opsonin proteins prevailed during the first type of adsorption. Their adsorption occurred on a dense and inactive layer of triblock copolymers. The second type of adsorption occurred due to the hydrophobic effect on a dense and mobile layer, with low-molecular-weight proteins being predominantly adsorbed (monoadsorption). The third type of adsorption occurred on a loose layer of triblock copolymers. In this case, the adsorption of a large amount of proteins with a molecular weight of 10–500 kDa was observed, while the total molecular weight was distributed over a large number of proteins.

We studied the effects of taurine chloramine and its structural analogues, antiplatelet agents, on the tertiary structure of bovine serum albumin by recording changes in its fluorescence spectrum. BSA was chosen as a model of the extracellular part of the purine P2Y12 receptor in platelets. For the detection of weak spectral shifts of the protein fluorescence, the index, which represents the ratio of the two light sums measured from approximately the middle of the spectrum towards the short- and longwave limits of its registration, was used. Administration of N-chlorotaurine and its analogues N-acetyl-N-chlorotaurine and N-isopropyl-N-chlorotaurine in albumin solution in equimolar concentrations cause weakening and red shift of the tryptophanyl fluorescence of the protein, indicating reorganization of the protein’s tertiary structure, thereby changing the properties of the microenvironment of tryptophan residues, primarily, Trp 134. All these changes are probably due to a covalent modification of the sulfhydryl group of Cys34 residue. It was hypothesized that chloramines of taurine have the ability to inhibit the activity of the ADP P2Y12 receptor in platelets due to the modification of its sulfhydryl group and that the inhibitory effect on the ADP-binding site has an allosteric character.

MiRNAs are small endogenous noncoding RNAs that inhibit protein expression at the translation level via complementary binding to a specific site in the mRNA. Most of the functional binding sites (miRNA nucleotides 2–7) located within the 3' untranslated region are conserved. These sites are predicted using the methods of comparative genomics, primarily, multiple sequence alignment. However, multiple sequence alignments are prone to accumulating errors due to strong divergence of species. Moreover, in the course of evolution, binding sites can migrate along the sequence. The aim of this work was to estimate the portion of conserved miRNA-binding sites that cannot be predicted using the existing tools because of these phenomena. The concept of L-conserved sites is introduced: a site is termed L-conserved if it is present in each sequence in the alignment within a frame of length L. We observed a significant increase in the number of additionally detected conserved sites without loss of sensitivity. The effect of species divergence on this increase was also evaluated.

A study was made of spontaneous surface birefringence observed in pullulan films when a tilted polarized beam is passed through a plain polymer film. Birefringence was explored as a function of the angle of beam incidence and the film thickness. The orientational order parameter was estimated for pullulan chains located in the near-surface layers of films. The results were compared with data from earlier studies of other polysaccharides.

Most higher eukaryotes are diploid organisms. Most genes are expressed from both chromosomal copies, but there are several important exceptions, in particular, the X-chromosome in mammals, imprinted genes, or genes of the immune system. In some cases, it was shown that the functioning of only one gene copy is determined by the interaction between its sense and antisense transcripts. In this work, a minimal model of strictly monoallelic expression is proposed and analyzed.

The effects of Т1⁺ ions on the dynamics of intracellular Cа²⁺ in neonatal rat cardiomyocytes have been studied. It was shown for the first time that application of Т1⁺ led to an uncontrolled increase in [Cа²⁺]_i in cells. Moreover, the ability of Т1⁺ to increase [Cа²⁺]_i depended on the Т1⁺ concentration used and the time of exposure to the cells. The increase in [Cа²⁺]_i was related to the entry of Cа²⁺ from the extracellular medium. Thallium did not release Cа²⁺ from intracellular stores. The thallium-induced increase in [Cа²⁺]_i was not inhibited by nifedipine. It is possible that L-channels do not participate in the processes of thalliuminduced increase in [Cа²⁺]_i. It is assumed that the thallium ions-induced calcium overload in cardiomyocytes may contribute to the toxic effect of Т1⁺ on the myocardium.

The kinematic characteristics {f(v), A(v), w(v)} allow a first-approximation representation of locomotor synergies in the swimming of fish: f is the frequency of the transverse oscillations, A is the amplitude of the caudal fin sweep, w is the velocity of the locomotor wave, and v is the locomotion speed. The additional compared characteristics included the step length L(v) and the wavelength λ(v), where L ≡ vT is the distance covered by the fish during the period T ≡ 1/f, and λ ≡ wT. These kinematic characteristics were derived from video recordings of swimming in six fish species. Three of the species investigated belonged to the anguilliform type, while the three others belonged to the carangiform type. The constant value of the wavelength λ at all speeds v was the common feature of the two types. The anguilliform fish performed a oneparameter version of locomotion control: the locomotion speed v changed due to the change of the wave velocity w and the undulatory amplitude remained constant. The carangioid fish used a two-parameter version of control, with changes in both the wave velocity w and the amplitude of undulations of the body and tail fin.

We investigated the effect of KB-R7943, an inhibitor of the reverse mode of Na⁺/Ca²⁺ exchanger, on the force of isometric contractions, the contractile force–frequency relationship and post-rest potentiation (a qualitative parameter of Ca²⁺ levels in sarcoplasmic reticulum) in the right ventricle papillary muscles isolated from ground squirrel hearts during summer (June, n = 4) and autumn (October, n = 4) activities. In the presence of 1.8 mM Ca2+at 36°C, 1–1.5 hours-long treatment of the summer papillary muscles with KB-R7943 produced no significant effects on the contractile indices at the majority of stimulation frequencies. In the autumn papillary muscles KB-R7943 induced a 40–50% decrease in the force of contraction (negative inotropic effect) at low stimulation frequencies (0.1–0.3 Hz) without any significant effect at higher stimulation frequencies (0.4–3.0 Hz). Furthermore, in this group, KB-R7943 suppressed the post-rest potentiation of contractility by 50 ± 21% at pause durations exceeding 120 s. These observations indicate that KB-R7943 can affect Ca²⁺ levels in sarcoplasmic reticulum and that Na⁺/Ca2⁺ exchange may contribute to the physiological remodeling of intracellular Ca²⁺ homeostasis in myocardium of hibernating animals prior their transition to a hypometabolic torpid state.

Regression analysis has been used to model the combined influence of adverse factors, namely, specific variants of the CRP (rs1130864), IFNG (rs2430561), TGFB1 (rs1982073), FGB (rs1800788), and PTGS1 (rs3842787) genes; age; and smoking on the risk of myocardial infarction in men, as well as the possible interactions between these factors. The individual effects of each considered genetic factor were comparable in strength to the influence of smoking on the risk of myocardial infarction, and the presence of a combination of two or more genetic variants in nonsmokers resulted in a higher risk of myocardial infarction than in noncarrier smokers. A significant interaction between the presence of the FGB allele rs1800788*T and age was discovered; the protective effect of this allele decreased with age and gradually transformed into a predisposing effect. The study demonstrated that the association of FGB rs1800788*T with the risk of myocardial infarction should be considered only in the context of interaction with age.

This work focuses on the study of remote effects (duration of remission, recurrence rate, and average lifespan) in mice with Ehrlich ascites carcinoma exposed to oligofractionated irradiation with a pencil scanning beam of protons depending on the volume of the tissue being irradiated and the interval between dose fractions. The results show higher antitumor efficacy and a considerable increase in the average life span of mice after hypofractionated irradiation with a pencil scanning beam of protons at a total dose of 60 Gy of the gross tumor volume compared with the planning target volume.

No adequate models for the effect of “repetition without repetition,” as discovered by N.A. Bernshtein in 1947, have been developed. This problem goes beyond the scope of the biomechanics and biophysics of movement and applies to all homeostatic systems. Its essence lies in the absence of both stationary modes (dx/dt = 0) and stable distribution functions f(x_i) (obtained by sequential registration of samples) for any component x_i of the state vector of a complex biological system x(t) = (x₁, x₂, …, x_m)^T: that is, x_i do not coincide! Simple models of such homeostatic systems represented as pairwise comparison matrices for the samples are proposed; these models can characterize a specific type of chaos that exists in biological systems. This chaos is different from deterministic chaos and is currently being tested as an approach for the description of complex biological systems (complexity).