Triplet state of the primary donor in reaction centers of the phototrophic bacterium <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis> R26 with active photoinduced electron transfer

EPR characteristics of transient paramagnetic states photoinduced in isolated reaction centers of Rhodobacter sphaeroides R26 with intact electron transfer have been studied. It was demonstrated that the detected weak triplet state EPR signal belongs to the primary donor molecule and is populated via the conventional mechanism of radical pair S-T₀ mixing. The distortion of the spectral shape of this signal is explained by the triplet quantum yield anisotropy brought about by the short lifetime of precursor radical pairs. The angular dependence of the anisotropy was evaluated. It was shown that the spectral shape of the triplet state of photosystem II reaction center observed in the case of singly-reduced primary quinone acceptor can also be described by the anisotropic quantum yield of the triplet, with practically the same angular dependence. These properties confirm the conclusions on the mechanism of photoinduced electron transfer in photosystem II, made in previous publications. The peculiarities in the functioning of photosystem II reaction centers are probably determined by strict limitations on the triplet state generation.     

Generation of reactive oxygen species in water under exposure of visible or infrared irradiation at absorption band of molecular oxygen

It is found that in bidistilled water saturated with oxygen hydrogen peroxide and hydroxyl radicals are formed under the influence of visible and infrared radiation in the absorption bands of molecular oxygen. Formation of reactive oxygen species (ROS) occurs under the influence of both solar and artificial light sourses, including the coherent laser irradiation. The oxygen effect, i.e. the impact of dissolved oxygen concentration on production of hydrogen peroxide induced by light, is detected. It is shown that the visible and infrared radiation in the absorption bands of molecular oxygen leads to the formation of 8-oxoguanine in DNA in vitro. Physicochemical mechanisms of ROS formation in water when exposed to visible and infrared light are studied, and the involvement of singlet oxygen and superoxide anion radicals in this process is shown.     

Study of the mechanisms of cytotoxic effect of uranyl nitrate

The mechanisms of cytotoxic effect of uranyl nitrate were studied. It was shown that uranyl nitrate induced HEp-2 cell death, mainly by necrotic way. In the experiments in vitro, uranyl nitrate caused an appearance of 8-oxoguanine in DNA, indicating the induction of oxidative stress. The experiments with isolated rat liver mitochondria revealed that 1 mM uranyl nitrate decreased the respiration rates of mitochondria in state 3 and DNP-induced respiration. At the same time, uranyl nitrate had no influence on the opening of the mitochondrial permeability transition pore and decreased the rate of formation of H₂O₂ by mitochondria. Possible molecular mechanisms of uranyl-induced necrosis are discussed.     

Generation of reactive oxygen species in water under exposure to visible or infrared irradiation at absorption bands of molecular oxygen

It is found that in bidistilled water saturated with oxygen, hydrogen peroxide and hydroxyl radicals are formed under the influence of visible and infrared radiation in the absorption bands of molecular oxygen. Formation of reactive oxygen species (ROS) occurs under the influence of both solar and artificial light sources, including the coherent laser irradiation. The oxygen effect, i.e. the impact of dissolved oxygen concentration on production of hydrogen peroxide induced by light, is detected. It is shown that the visible and infrared radiation in the absorption bands of molecular oxygen leads to the formation of 8-oxoguanine in DNA in vitro. Physicochemical mechanisms of ROS formation in water when exposed to visible and infrared light are studied, and the involvement of singlet oxygen and superoxide anion radicals in this process is shown.     

Morphological study of cysts of Pelomyxa palustris Greeff, 1874

Pelomyxa palustris Greeff, 1874, is the only representative of pelomyxoid amoebae with rest cysts in its life cycle. The morphology of the P. palustris cysts was studied using light and electron microscopy. The encystation of P. palustris under the climatic conditions of northwestern Russia occurs in August through September. The rest of the cysts have complex, trilaminar walls. The most developed are the two inner layers, i.e., the electron-dense structureless endocyst and the laminated mesocyst; the thickness of each layer can reach 0.6–0.7 μm. The thickness of the superficial electron-dense ectocyst lamina usually does not exceed 0.1–0.2 μm. The encysted cell of P. palustris has a unique structure. About 60% of its cell volume is occupied by a giant central vacuole filled with prokaryotic cytobionts. This vacuole has also been found to contain vacuoles and vesicles of different natures, restricted by vacuole membranes, autophagosomes, and lipid droplets. The amoeba cytoplasm occupies the space between the endocyst inner surface and the central vacuole. It contains no inclusions, prokaryotic cytobionts and most of cell organelles. In the cytoplasm there are 4 large nuclei filled with relatively homogeneous karyoplasm. The nuclear envelope forms numerous long tubular outgrowths, piercing the cytoplasm and underlining the central vacuole membrane. In this state the encysted pelomyxoids survive until the beginning of excystation. The excystation of P. palustris in the studied region occurs in spring, during the second half of April through the beginning of May. The cysts undergo complex morphofunctional changes due to reorganization of the wall and formation of young multinucleate amoebae. Out of the three initial lamina of the wall, only one persists until the moment of encystation. The central vacuole is destroyed and its content penetrates into the cytoplasm. Pelomyxoid nuclei divide twice. Prokaryotic cytobionts are localized in the cytoplasm and in the perinuclear area. Young multinuclear P. palustris individuals exiting cysts do not differ from the adult forms by their organization.     

LINE1 Derepression in Aged Wild-Type and SIRT6-Deficient Mice Drives Inflammation

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Overexpression of L7/L12 protein with mutations in its flexible region.

Using restriction enzymes and polymerase chain reaction, three mutated forms of L7/L12 proteins with deleted 38-46, 44-52 and 38-52 residues were obtained. These mutant proteins were isolated in a preparative scale and were shown to bind to ribosomes and to affect ribosomal function.     

Structure and density of ribosomal RNA and its complexes with proteins in a solution

X-ray and neutron scattering, as well as velocity sedimentation, were used to study the shape and dimensions (compactness) of isolated ribosomal (16S and 23S) RNA's and their complexes with ribosomal proteins. The neutron scattering of ribosomal particles in 42% 2H2O where the protein component is contrast-matched, were taken as a standard of comparison characterizing the dimensions and shape of the 16S and 23S RNA in situ. This comparison allowed the following conclusions: (1) The shape of the isolated 16S RNA at a sufficient Mg2+ concentration (e. g., in the reconstruction buffer) is similar to that of the 16S RNA in situ, but its compactness is somewhat less. (2) The 16S RNA in the complex with protein S4 has a shape and compactness similar to those of the isolated 16S RNA. (3) The 16S RNA in the complex with four core proteins, namely S4, S7, S8 and S15, has a shape and compactness similar to those of the isolated 16S RNA. (4). The six ribosomal proteins, S4, S7, S8, S15, S16, and S17, are necessary and sufficient for the 16S RNA to acquire a compactness similar to that in situ.     

Amplification of portions of the genome in mammalian somatic cells resistant to colchicine. VI. Restriction analysis of the amplified DNA sequences

Fragments specific for the amplified regions in DNA of Djungarian hamster colchicine-resistant cells were studied after restriction endonuclease digestion. We used three different methods of detection of these fragments: a) comparison of the wild type and resistant cell DNA electroforegramms stained by ethidium bromide; b) blotting of DNA from sensitive and resistant variants onto nitrocellulose filters and their hybridization with nick-translated DNA from resistant cells, in the presence of the excess of unlabelled DNA from the wild type cells (competitive hybridization); c) investigation of autonomously replicating DNA from sensitive and colchicine-resistant sublines. The highest resolution was found using the third method. However, the competitive hybridization is evidently a more universal approach to restriction analysis of DNA amplified sequences, because it gives quite high resolution and may be used for studying both autonomously and non-autonomously replicating sequences.