Dinucleosome as a product of initial chromatin cleavage by endogenous nucleases

The ability of nucleic endonucleases to recognize dinucleosomal level of chromatin structure was studied. Rat liver chromatin endonucleases were shown to be capable of DNA cleavage at dinucleosome linkers. The cleavage was observed mainly at initial stages of chromatin autohydrolysis, i.e. up to 10-20th min of incubation in the medium containing 5 mmol of magnesium chloride and 2 mmol of calcium chloride. Thus, mononucleosomal DNA in dinucleosomes and other even chromatin subunits was larger and more homogeneous than in odd subunits. The cleavage of autodigested chromatin by bovine spleen and snake venom exonucleases and by nuclease S1 has shown that dinucleosomal structure is independent of differences in the length of internal and external dinucleosome linkers. The initial endonucleolysis appears to be characterized by different accessibility of the linkers for chromatin nucleases.     

Assessment of iron toxicity using a luminescent bacterial test with an Escherichia coli recombinant strain

The toxic effect of the Fe²⁺ and Fe³⁺ ions on the luminescent recombinant Escherichia coli strain with the luxCDABE operon was studied in short- and long-term experiments. At 30-min exposure of bacteria to the iron ions, the effective concentrations of Fe²⁺ and Fe³⁺ resulting in acute toxicity (EC₅₀) were 8.5 and 1.3 mg/L, respectively. In the long-term (24 h) experiment, during active bacterial growth, the toxicity index for Fe²⁺ and Fe³⁺ was 65.5 and 62.8, respectively. Addition of the iron ions into the medium did not suppress growth, although it inhibited luminescence. Comparative analysis of the short- and long-term experiments made it possible to assess iron toxicity at the concentrations from 0.5 to 20 mg/L (as calculated for the Fe²⁺ and Fe³⁺ ions). Iron ions were found to affect only the reactions that were not vitally important for the cell. At the same time, they had no negative effect on the genetic mechanisms and protein synthesis, thus indicating non-specific toxicity of Fe²⁺ and Fe³⁺.     

Manganese(III) and rhenium(II) complexes with bulky 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinonato ligands via carbonyls of corresponding metals

Four-coordinate complex Mn^III(ISQ-Prⁱ)(AP-Prⁱ) (1), where ISQ-Prⁱ = 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzosemiquinonate anion-radical, AP-Prⁱ = 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolate dianion, has been prepared by the reaction of Mn₂(CO)₁₀ with free 4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-iminobenzoquinone (IBQ-Prⁱ) in the molar ratio 1:4 in toluene. In contrast to manganese, rhenium carbonyl reacts with o-iminobenzoquinone to form complex Re^II(ISQ-Prⁱ)₂(CO)₂ (2) with the retention of two carbonyls in coordination sphere of rhenium. The complexes have been characterized by IR, UV-Vis, and EPR spectroscopies. Molecular structures of compounds 1 and 2 have been determined by single-crystal X-ray crystallography. Compound 1 is centro-symmetric square-planar molecule with delocalized mixed valent state of AP-Prⁱ and ISQ-Prⁱ ligands. EPR spectrum of 1 in solid at 300-77 K is typical for manganese complexes with S = 3/2 state. The effective magnetic moment of 1 is 1.96 μ_B at temperature 5 K as it was established by variable-temperature magnetic susceptibility measurements. Six-coordinate octahedral complex 2 possesses an S = 1/2 ground state, which is attained via strong intramolecular antiferromagnetic interaction between t_2g orbital unpaired electron of the low spin Re^II ion and the unpaired electron on π-orbital of the radical ligand.     

A study of the interaction of boraadamantane with liposomes

Changes in the surface potential of liposomes obtained from dipalmitoyl phospatidylcholine during their interaction with the new antiviral preparation boraadamantane (BG-12) have been studied. It has been concluded that the saturation of the lipid bilayer of liposomes by the BG-12 preparation occurs at its concentrations above 10 μg/mL.     

Assessment of the Safety of Lactobacillus casei IMV B-7280 Probiotic Strain on a Mouse Model

Probiotics, in particular Lactobacillus (lactic acid bacteria, LAB) strains, are widely used in clinical practice. Despite that these probiotics have GRAS (generally regarded as safe) and qualified presumption of safety (QPS) statuses, the safety of particular strains still needs to be thoroughly studied. The aim of the study was to evaluate the safety of Lact. casei IMV B-7280 strain by investigating toxicity and the effects on gut microbiota in experimental animal model. Male BALB/c mice (7–8 weeks, weight 20–24 g) were treated with amounts of Lact. casei IMV B-7280 strain: 5 × 10⁶, 5 × 10⁸, or 5 × 10⁹ CFU/animal once per day during 7 days, or in the amount of 1 × 10¹⁰ CFU/animal once per day during 3 days (most of the proposed probiotic doses for humans—from 10⁸ to 10⁹ CFU) and monitored during 14 days. Blood tests and serum biochemistry were conducted; the cecal content from mice of the experimental and control groups were freshly collected and analyzed. At the end of the experiments (15th day), the presence of LAB in the heart, liver, kidney, and mesenteric lymph nodes and peripheral blood was determined; histology of the brain, liver, heart, fragments of the small and large intestine, and mesenteric lymph nodes was conducted. Survival rate of BALB/c mice treated with Lact. casei IMV B-7280 strain in different concentrations in toxicity experiments during 14 days was 100%. We observed no signs of toxicity as changes in gait, lethargy, sleep, somatomotor activity as well as changes in fur, eyes, skin and mucous membranes, tremors, behavior pattern, convulsions, salivation, diarrhea, and local injuries in mice from all experimental groups. After administration of probiotic strain, the number of opportunistic bacteria in cecal contents, such as Staphylococcus spp., Candida spp., Pseudomonas spp., and total aerobic and optionally anaerobic bacteria decreased compared to controls; the population of beneficial bacteria such as lactobacilli increased in cecal contents of these mice. LAB were not detected in the peripheral blood, heart, liver, kidneys, and mesenteric lymph nodes after administration of this strain to intact mice. Lact. casei IMV B-7280 strain is safe at dose up to 10¹⁰ CFU/animal during 3- and 7-day oral administration to mice and has a positive effect on the gut microbiota composition; it could be potentially considered as safe probiotic for humans.

     

Conditions for initial chromatin endonucleolysis and the characteristics of its products

The restricted initial autohydrolysis of chromatin is used for obtaining its matrix-active fractions. Application of the method for isolating cell nuclei in the presence of 10 mM CaCl2 makes it possible to appreciably inhibit the cleavage of chromatin DNA in the course of isolation, namely to 0.9% according to the acid-soluble fraction. It is shown that at the initial stages of autohydrolysis the method of solubilization is by one order of magnitude more sensitive as compared to the measurement according to the acid-soluble fraction. Initial autohydrolysis is characterized by rapid increment of the amount of the solubilized fraction, delayed formation of mononucleosomes and by the capacity to a 20% activation in the presence of 10(-5) M histamine.     

The first monoribbed-functionalized tris-dioximate iron(II) clathrochelate with two inherent NH2-substituents, its reactivity, acid-base and coordination-chemical properties

The diamine bis-α-benzildioximate iron(II) clathrochelate with two inherent NH₂-groups at one of the three ribbed fragments was obtained in a high yield by nucleophilic substitution of the dichlorine-containing macrobicyclic precursor with liquid ammonia. These amino-groups have an essential amide character and undergo deprotonation in the presence of strong bases. The resulted clathrochelate dianion behaves as an acido-ligand and coordinates to copper(II) ion giving the heteronuclear copper(II)-iron(II) complexes with the Cu(N⁻)₄ coordination polyhedron. The reaction of this dianion with benzil afforded the clathrochelate product with annulated heterocyclic ribbed piperazinone fragment as a result of benzilic-type rearrangement with 1,2-shift of the phenyl substituent.The complexes obtained have been characterized using elemental analysis, MALDI-TOF, IR, UV-Vis, multinuclear NMR and EPR spectra, and X-ray crystallography. N₆-coordination polyhedra of their encapsulated iron(II) ions possess a distorted trigonal-prismatic geometry.     

Synthesis, X-ray structure and redox properties of the macrobicyclic iron(II) N2- and S2-containing vic-dioximates

Nucleophilic substitution of the reactive chlorine atoms of the boron-capped macrobicyclic vic-di- and hexahalogen-containing iron(II) precursors with 1,2-ethanedithiol and 1,2-benzenedithiol in dichloromethane as a solvent in the presence of triethylamine as a strong organic base afforded the corresponding di- and hexasulfide mono- and triribbed-functionalized clathrochelates, respectively, in relatively high yields. In the case of the low-reactive tin-capped clathrochelate [Fe(Cl₂Gm)₃(SnCl₃)₂]²⁻ dianion this reaction was performed in DMF with the potassium salt of 1,2-benzenedithiol. The reaction of the dichlorine-containing FeBd₂(Cl₂Gm)(BF)₂ precursor with an excess of ethylenediamine in DMF led to the clathrochelate with N₂-containing vic-dioximate ribbed fragment. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV-vis, ¹H and ¹³C{¹H} NMR, ⁵⁷Fe Mössbauer spectroscopies, and X-ray crystallography.The nature and number of the ribbed substituents affect the geometry of a clathrochelate framework, first of all, the distortion of the trigonal prismatic-trigonal antiprismatic iron(II) coordination polyhedra, whereas the apical substituents at the capping boron atoms influe on the B-O distances in the apical RBO₃ fragments. The geometry of the tin-capped hexasulfide clathrochelate complex was deduced from EXAFS data using the scattering both on the encapsulated iron(II) and capping tin(IV) ions.The electrochemical properties of the iron(II) complexes obtained were studied by cyclic voltammetry. The electrochemically generated unstable reduced anionic forms are destabilized by the electron-donating ribbed substituents, whereas the oxidation led to the formation of the cationic macrobicycles, the stability of which depends on the nature of the apical capping groups and ribbed substituents as well. The pseudo-aromatic disulfide ribbed fragments stabilize the oxidized forms of the clathrochelate complexes.     

Effect of rarely repeated immobilization episodes on hypoxia-tolerance and anxiogenic stress severity

4 episodes of immobilization stress (60 minutes, once 72 hours) led to diminution of hypoxia tolerance and anxiety-depressive disorders of behavior. The later shifts were associated with decrease of IL-4 concentration and simultaneous increase of IL-6 level in blood serum. The stress-induced behavioral shifts appeared to correlate with IL-4 concentration in blood of stress-sustained rats.