Biofizika最新文献

Two mechanisms responsible for the emergence of arrhythmia are known: a change of part of the cells to a self-oscillatory mode and generation of circulating waves. In this paper, we investigate the generation mechanism of the circulating waves using the unidirectional block. One of the variants of its realization is a narrow gap between two non-conducting regions. Implementation of this mechanism in the human heart turns out to be impossible, since in the heart in which the duration of cardiac action potential lasts 0.3 s and the velocity of wave propagation is equal to 33 cm/s, the minimal length of the pathway for wave circulation is approximately 10 cm, while the distance between the ventricular apex and atrioventricular septal is, on the average, 8 cm. Therefore, that inhomogeneity cannot exist at the scale of human heart. To adapt this mechanism to the size of the human heart, we introduce into the scheme the regions with low conductivity, which provide slow propagation of the wave. The value of conductivity is chosen based on the results of evaluation of the "conductivity-wave velocity" correlation. The analysis of wave propagation through the boundary between two regions with different conductivities has shown that the refractory period depends on the conductivity ratio. To minimize this dependence we introduce the transition zone, in which conductivity changes linearly from some normal value to a reduced one. This allowed us to generate a 12-mm inhomogeneity area, provoking the appearance of the circulating wave.

In this paper, we present the results of experimental studies on the influence of different magnesium isotopes, the magnetic 25Mg and nonmagnetic 24Mg and 26Mg on ATP activity of the isolated myosin subfragment-1. The reaction rate in the presence of magetic 25Mg isotope turned out to be 2.0-2.5 times higher than that using nonmagnetic 24Mg and 2 Mg isotopes. No magnetic isotope effect was observed in the absence of the enzyme as in spontaneous ATP hydrolysis in aqueous solution. Hence, a significant catalytic effect of the magnetic 25Mg isotope (nuclear spin catalysis) was observed in the enzymatic hydrolysis of ATP.

This paper briefly reviews the ways of activation of the antitumor resistance mechanisms developed on the basis of the concept of the periodic system of general nonspecific adaptational reactions of the body. The principles of the formation of effective influences by electromagnetic radiation using biologically active substances are described. A comparison of the criteria and conceptions of the theory of adaptational reactions to some concepts and categories of synergetics is made. The features of dynamics of the studied parameters upon effective influences are considered. Antistress nature of the systemic effects of ferromagnetic nanoparticles on tumor bearing animals is shown. The, possible mechanisms of regression of large tumor under the influence of two different factors--modulated electromagnetic radiation and magnetite nanoparticles--are discussed. The cases of a change of the order parameter in connection with the development of antistress areactivity and regression of experimental tumors under the influence of the combined electromagnetic impact are analyzed.

It is known that in quantum mechanics the act of observing the experiment can affect the experimental findings in some cases. In particular, it happens under the so-called Zeno effect. In this work it is shown that in contrast to the "standard" Zeno-effect where the act of observing a process reduces the probability of its reality, an inverse situation when a particle transmits through a potential barrier (a so-called barrier anti-Zeno effect) can be observed, the observation of the particle essentially increases the probability of its transmission through the barrier. The possibility of using the barrier anti-Zeno effect is discussed to explain paradoxical results of experiments on "cold nuclear fusion" observed in various systems including biological ones. (According to the observers who performed the observations, the energy generation, which could not be explained by any chemical processes, as well as the change in the isotope and even element composition of the studied object may occur in these systems.

The structure of three forms of a dimeric enzyme, human inosine triphosphate pyrophosphatase, is considered to identify the enzyme conformation changes causing the inactivation effect of a P32T mutation. Analysis of a nanosecond molecular dynamics is performed; the mean square deviations of the atoms between the wild-type and mutant homodimers, and also the heterodimer are calculated. A 3 ns modeling shows a greater displacement of atoms in mutant protomers. During molecular dynamics simulation, the strongest changes are observed in the loop between α2 and β2 (amino acid residues 28-33, an area of the P32T mutation), the loop between β5 and β6, and the C-terminal amino acid residues. The loop between (α2 and β2 has two conformations characterized by different positions of the Phe31 aromatic group. The distance between Cys33 (Cα) and Phe31 (C(z)) for wild-type and mutant protomers was -9 and 5.5 Å, respectively. These conformations were kept constant.

In this study we suggested a dynamics simulation for the formation of protofiber of spider web nanofiber. It was shown that a bundle of parallel polyalanine β-strands of sufficient length is arranged through self-assembly into a stable right-handed super helix. By numerical analysis we investigated the rheological properties and provided in nonlinear regime a generalization of the model of Singer for description of the rheological behaviour of super helix.

The paper presents analysis of a study of the polarized component of the reflectance factor (Rq) and the degree of polarization (P) of wheat and maize crops depending on the wavelength. Registration of polarization characteristics was carried out in the field from the elevated work platform at heights of 10 to 18 m in June and July. Measurements were performed using a double-beam spectrophotometer with a polarized light filter attachment, within the spectral range from 400 to 820-nm. The viewing angle was no greater than 20 degree with respect to the nadir. The reflection spectra of wheat and maize crops obtained using a polarizer adjusted to transmit the maximum and minimum amounts of light (R(max) and R(min)) were studied. Based on these reflection spectra polarization characteristics, which. differ in the visible and infrared spectral region, were determined and analyzed.

According to Gibbs J.W. the number of independent components is the least number of those chemical constituents, by combining which the compositions of all possible phases in the system can be obtained, and at the first stages of development of the primary metabolism of the three-component system C-H-O different hydrocarbons and molecular hydrogen were used as an energy source for, it. In the Archean hydrothermal conditions under the action of the phosphorus chemical potential the C-H-O system was transformed into a four-component system C-H-O-P setting up a gluconeogenic system, which became the basis of power supply for a protometabolism, and formation of a new cycle of CO2 fixation (reductive pentose phosphate pathway). It is shown that parageneses (association) of certain substances permitted the modular constructions of the central metabolism of the system C-H-O-P and the formed modules appear in association with each other in certain physicochemical hydrothermal conditions. Malate, oxaloacetate, pyruvate and phosphoenolpyruvate exhibit a turnstile-like mechanism of switching reaction directions.

Currently, biophysical mechanisms of stress signaling transduction became an object of consideration of researchers in connection with the urgent necessity to develop new techniques to enhance the sustainability and productivity of agricultural crops. The development of sensitive methods for the determination of cyclic guanosine monophosphate (cGMP) and comparative analysis of cGMP-dependent events in biological systems has contributed to progress in the understanding of the functioning of cGMP in plant cells. Currently, it is shown that cGMP as a secondary mediator is involved in such vital processes of growth and development of plants as seed germination, cell division, development of chloroplasts, flowering and regulation of stomatal movements. This review summarizes the available data in the literature about the role of cGMP in the responses of plant organisms to the action of stress factors of abiotic and biotic nature and its interaction with other intracellular mediators. With the use of existing ideas about the biophysical mechanisms of stress in plants, the basic elements of cGMP-dependent signal transduction system in a plant cell are considered.

Experimental results of the study on causes of the difference in thermal conductivity coefficient of water under water heating by a biological object (operator hand) compared to heating by an electric radiator of the same temperature are given. Two possible causes of the observed effect, which are associated with the difference in the spectral composition of radiation generated by the operator hand compared to an electrical source of heat and solubility in water of CO2 released from human skin, are discussed.