Biophysics最新文献

Possible conformations of the soymorphin-6 molecule (Tyr1–Pro2–Phe3–Val4–Val5–Asn6—NH₂) have been studied by theoretical conformational analysis. The potential function of the system was chosen as the sum of nonvalent, electrostatic and torsion interactions and the energy of hydrogen bonds. Low-energy conformations of the soymorphin-6 molecule have been found, the values of the dihedral angles of the main and side chains of amino-acid residues that make up the molecule, and the energy of intra- and inter-residual interactions has been estimated. It was shown that the spatial structure of the soymorphin-6 molecule is represented by conformations of eight shapes of the peptide skeleton. The results we obtained can be used to elucidate the structural and structural-functional organization of soymorphins.

An efficiency of oxygen release from red cells strongly depends on the regimes of their motion through microvessels. Mathematical model of oxygen transfer taking into account the red cells ability to form intravascular sludges has been constructed and studied. An analytical expression for the dependence of the oxygen release intensity on the size of erythrocyte sludges were derived. The possible significance of the obtained results for the express diagnostics of the red cell’s ability for an oxygen transmission is discussed.

A comprehensive spectral analysis of heart rate variability and skin perfusion of the extremities in patients with type 2 diabetes mellitus in response to local heating and identification of significant predictors of pathophysiological changes in the cardiovascular system has been carried out. Electrocardiogram and skin perfusion on the forearm and foot were measured by laser Doppler flowmetry at rest and under local heating in healthy individuals and diabetic patients. The signals of laser Doppler flowmetry and heart rate variability (according to electrocardiographic data) were subjected to wavelet analysis. Receiver operating characteristic analysis was used to evaluate significant predictors. It was found that in patients, compared with healthy individuals, there was (1) a decrease in the reserve of cutaneous blood flow on the foot under heating, (2) a decrease in the amplitudes of heart rate oscillations at rest and under heating, (3) an increase in the amplitudes of oscillations of laser Doppler flowmetry signals on the forearm in respiratory intervals and cardiac intervals at rest and under heating, and (4) a decrease in the amplitudes of oscillations of laser Doppler flowmetry signals on the foot in the myogenic interval at rest and in the cardiac interval under heating. The parameters of the cardiovascular system (the energy of heart rate variability in the low frequency interval and oscillations of laser Doppler flowmetry signals on the forearm in respiratory interval, which can serve as markers for early diagnosis of microvascular disorders) with high discriminatory power to distinguish patients and healthy individuals in response to local heating were revealed.

It has been shown that a decrease in background production of reactive oxygen species in peritoneal neutrophils of mice after a short-term (40 min) stay in hypomagnetic conditions (residual field of ~10 nT) at physiological temperatures, detected by the method of lucigenin-dependent chemiluminescence, was not accompanied by a violation of the chemiluminescent response to respiratory burst activators of formylated peptide N-formyl–Met–Leu–Phe (fMLP) and forbol ether forbol-12-meristate-13-acetate (FMA). These results were obtained by activated chemiluminescence method using lucigenin and luminol and various combinations of activators for the production of reactive oxygen species (forbol-12-meristate-13-acetate and/or N-formyl–Met–Leu–Phe). The study, together with the previously obtained results, makes it possible to exclude the systems controlling the respiratory burst in neutrophils from the main targets and acceptors that react to short-term deprivation of a magnetic field.

A theoretical analysis of the literature data on the pulse-wave propagation velocity using a combination of electrocardiographic and photoplethysmographic signals was carried out. Its diagnostic value in medical practice lies in its use as a noninvasive method for measuring blood pressure, as well as for determining arterial stiffness. Some studies have shown a relationship between the velocity of pulse-wave propagation and risk factors for cardiovascular diseases. Pulse-wave propagation velocity is an early marker and predictor of cardiovascular risk in both people with normal blood pressure and people with hypertension; it is used as the “gold standard” in determining arterial stiffness; however, the issue of accuracy and automation of measuring the pulse-wave propagation velocity remains unresolved.

A comparative study of the cytotoxic activity and mechanism of action of polyacrylates containing gold (aurumacryl) and silver (argacryl) against human tumor cells (MCF-7 cell culture) has been carried out. The high cytotoxic activity of the drugs has been shown. Argacryl was found to be 20 times more effective than aurumacryl. It was found that apoptosis was the dominant mechanism in the death of tumor cells induced by aurumacryl and argacryl. Differences in the effect of drugs on the DNA structure of tumor cells were revealed.

The article expounds, with examples, how to apply the computer method of arterial piezo pulsometry designed to provide a rapid noninvasive test for the functional state and the nature of autonomic regulation of the cardiovascular (CV) system in patients varying in age and health status. The involvement and role were assessed for the contractile component of left ventricular (LV) myocytes as a universal muscle effector that ensures both the basic pumping function of the heart and the implementation of the autonomic regulation of heart contractions via peripheral neurohumoral mechanisms that maintain the optimal level of cardiac hemodynamics. The analysis was found to enhance the predictive value of early noninvasive pulsometric diagnosis of the individual functional state and the nature of the regulation of the human CV system during ontogeny. This knowledge helps identifying the risk that may threaten the evolutionary ability of the CV system to maintain a dynamic balance, self-regulation, and adaptation to changing environmental conditions and is associated with distorted homeostasis of the body.

A universal algorithm for calculating the initial velocities of enzymatic reactions at the “zero” moment of time according to the kinetic curve of substrate consumption or product accumulation during direct kinetic measurements of enzyme activity is presented. The study was performed using the example of a commercial lactate dehydrogenase preparation and a standard biochemical set of reagents. The proposed approach makes it possible to practically eliminate systematic measurement error, to determine the initial reaction velocity with equal accuracy regardless of the level of enzyme activity, to reduces the analysis time to 1 min, and to expand the scope of application of standard reagent kits for the study of samples of enzymes of different origin in solving a wide range of tasks. The algorithm cannot be applied when using conjugated enzyme systems in an analytical procedure, since in this case there is a long initial lag phase on the kinetic curves.

The chickpea Cicer arientinum is an important leguminous crop and is especially widely grown in the Near East. Because chickpea is highly susceptible to fungal diseases, such as Ascochyta blight and Fusarium blight, in wet weather conditions, disease-resistant and early-ripening varieties are critically important to breed. Genome associations were studied in 171 samples of chickpea plants grown in two experimental stations in Krasnodar krai (Kuban experimental station) and Astrakhan (Astrakhan experimental station). Relationships with genes were assessed for 12 phenotypic traits and 3 hallmarks of resistance to the pathogens Fusarium, Ascochyta, and Noctuidae. Variants associated with different phenotypic traits were identified using genome-wide association study (GWAS) methods.

β-Bends are a difficult to interpret type of polypeptide chain backbone structure of globular proteins. β-Bends are usually classified according to the dihedral angles φ and ψ of amino acid residues i + 1 and i + 2. Ramachandran map analysis of amino acid residues i + 1 and i + 2 indicates the resulting conformational stresses in bending. This kind of conformation stresses can only be compensated by additional interactions, such as additional hydrogen bonds, whose geometry and energy compensates for the β-bending stress. Neutronography is the only available direct method for determining the position of hydrogen atoms in the structures of chemical compounds, including proteins. In this work, β-bends from 176 protein structures from PDB established by neutronography are studied. In these structures, 3733 β-bends were found using the i → i + 3 hydrogen bonding criterion. Using clustering by the magnitude of conformational angles, eight types of bends were newly identified. The magnitudes of conformational angles for each type of bend were determined. The hypothesis of additional hydrogen bonding to stabilize the bend was not confirmed, suggesting that the bending stress is compensated by other factors.