Biofizika最新文献

From our earlier experiments on the study of changes in titin content and the level of its phosphorylation in skeletal muscles, atrophied during space flight, hibernation, and also because of the development of alcohol-induced lesions it has been suggested that an increase in the degree of titin phosphorylation results in increased proteolytic degradation of this protein, that contributes to the development of skeletal muscle atrophy.

The changes in the electro-acoustic parameters of cell suspension due to the interaction of cells with bacteriophages both in a pure. culture and in the presence of extraneous microflora were investigated. It has been found that the specific changes in the electroacoustic parameters of cell suspension under the action of bacteriophage occur only in microbial cells which are sensitive to the bacteriophage studied. It has been established that a sensor unit allows of distinguishing a situation when the bacterial cells are infected with specific bacteriophages of the control experiments and a situation with no introduction of infection. An approximate criterion of the presence of specific interactions of bacteriophages and cells in suspension was developed. In accordance with this criterion the change in electrical impedance of the sensor unit must not be less than - 1%. In control experiments a standard microbiological technique, plating the cells infected with bacteriophages on solid nutrient medium, was used. For the first time the possibility of using the method of electroacoustic analysis for determination of a spectrum of lytic activity of bacteriophages was shown. The results obtained may be used for development of a new express method for determining the sensitivity to bacteriophages of the microbial cells.

The joint application of the precise X-ray data for isolated bacteriochlorophyll complexes of reaction centers and the fundamental formulae for the energy of interaction between two equal dipoles enabled us to suggest a new methodical approach for determination of the values of the index of dielectric permeability in the micro volume enclosing special pairs in Rhodobacter sphaeroides reaction centers. The most probable value for this parameter was thus determined within 1.66-1.76. This approach was generalized for the inner layer of the membranes of purple bacteria and yielded the index value about 1.70-1.85. It is argued that this range of dielectric permeability is adequate for bacterial and plant membranes as well. Low magnitude of this parameter contributes to higher efficiency of energy migration from vast light-harvesting chlorophyll "antenna" to the energy converting reaction centers and hence to higher efficiency of the whole photosynthesis.

We consider a model for competitive species under spatial heterogeneity of resource and population. To analyze the possible scenarios of migration and distribution we employ a technique based on the cosymmetry theory and computational experiment. Coexistence of species and the cases of survival of-competitors are studied. The maps for migration parameters are found for different scenarios.

The search for ideal protective agents for use in a variety of radiation scenarios has continued for more than six decades. This review describes the history of the major discoveries, shows the chronology of the changes in attitudes, trends and paradigms. The readers are invited to meet with various classes of chemical compounds that have the potential to protect against acute and late effects of ionizing radiation when administered either before or after radiation exposure. The work represents characteristics of radioprotective agents such as a dose reduction factor, time of administration, tissue specificity, toxicity; the mechanisms of their action and practical applications are also described. A separate chapter considers the further development prospects and directions in this field of research.

The antioxidant enzyme peroxiredoxin 6 forms cation selective ion cluster-type channels in the lipid bilayer. Channel clustering as oligomeric structure consists of three or more subunits--channels with conductance of about 350 pS in the 200 mM KCl. Mean dwell time of the channel's open states decreases with increasing membrane voltage. A possible molecular mechanism of the observed potential-dependent inactivation of the channel cluster is discussed.

We present results of the analysis of long-term chlorophyll a dynamics in the Naroch lakes. It has been shown that an increase in nutrient load in the 1970s resulted in progressive eutrophication of Naroch lakes. Then, starting in the mid-1980s, the increase in water transparency and decreases in concentrations of phosphorus and nitrogen have been occurring due to the environmental improvement program. In the 1980s, the Naroch lakes experienced a strong factor as an invasion by zebra mussel (Dreissena polymorpha Pallas). Our analysis shows that responses of all three lakes to the intensive nutrient load and further decrease in the nutrient concentration as a result of the environmental protection measures have been correlated. At the same time, different degrees of the influence of the zebra mussel invasion on the lakes are shown to lead to divergence in chlorophyll dynamics. This divergence was observed as a drastic decline in correlations between variations in chlorophyll concentrations in every Naroch lakes.

The computer model for a dimer of inulinase from Aspergillus ficuum is designed. The permolecular organization of inulinase from Aspergillus niger is experimentally investigated. The question about the role of various inulinase forms in manifestation of their functional activity is discussed. It is shown, that in the process of inulinase dimerization when contacts between monomeric forms of the enzyme are formed, a key role belongs to the nonpolar amino acid residues.

The antioxidant effect of succinate and 3-hydroxybutyrate oxidation on the kinetics of lipid peroxidation induced by ATP-Fe2+ complex in isolated rat liver mitochondria of old (1.0-1.5 years) and young (3 months) male rats was investigated. The rate of induced lipid peroxidation V(LPO) in rat liver mitochondria and the half-time of oxygen consumption Δt50, which included the lag period and the initiation. phase, was recorded polarographically. Without exogenous oxidative-substrates V(LPO) was slightly higher in mitochondria of old animals, but the onset of lipid peroxidation cascade was significantly earlier than in young animals. Incubation of mitochondria with 5mM succinate for 1 min inhibited V(LPO) by 15% in young animals and by 35% in old animals. However, only in mitochondria of old animals Δt50 increased by 19% as compared to lipid peroxidation without substrates. V(LPO) in mitochondria of young animals did not significantly change during 3-hydroxybutyrate oxidation, while in mitochondria of old animals it was reduced by 19% with a slight increase in Δt50. To simulate age-dependent dysfunction we damaged isolated mitochondria by a series of freeze-thaw cycles, which caused a significant increase of V(LPO) of.both age groups. Succinate oxidation inhibited V(LPO) in damaged mitochondria in all cases by 56%, as compared to V(LPO) without oxidative substrates and extended At50 twofold in mitochondria of young animals. Oxidation of 3-hydroxybutyrate had no effect on V(LPO) in damaged mitochondria regardless of animal, age and extended Δt50 by 48% in mitochondria of young animals. Thus, the antioxidant effect of succinate oxidation can prevent lipid peroxidation damage and may exhibit geroprotective action at the level of aging mitochondria. Therefore, the antioxidant effect is due to the process of substrate oxidation in the respiratory chain but not because of an interaction of their structures with membrane lipids per se.

The Brownian dynamics method is used for qualitative analysis of events leading to formation of a functionally active plastocyanin-cytochrome f complex. Intermediate states of this process are identified by density-based hierarchical clustering. Diffusive entrapment of plastocyanin by cytochrome f is a key point of the suggested putative scenario of protein-protein approaching. Mobility of plastocyanin is characterized for different values of protein-protein electrostatic interaction energy.