Vol. 54 No. 2 (252) (2020)

The methods have been developed for the preparation of diheterocyclic systems of a new structure, such as pyrazolo- and 1,3,4-oxadiazolo-1,2,4-triazoles, based on S-substituted thioglycolic acid derivatives.

Bovine serum albumin (BSA) interaction with tannic acid (TA) has been studied in dimethylsulfoxide (DMSO) aqueous solutions at different temperatures (293 and 303 K). To find out the fluorescence quenching mechanism of BSA in the presence of TA, the fluorescence data were analyzed according to the modified Stern-Volmer equation based on the approach of the existence of a “sphere of action” (a type of apparent static quenching). The values of apparent static and bimolecular quenching constants were calculated. The effect of DMSO and temperature on BSA–TA interactions is explained on the basis of structural changes in the “sphere of action” of the fluorophore due to the possible inclusion of DMSO molecules in this sphere.

The formation of Cօ²⁺ : phenylalanine (Phe) 1:1 complex has been confirmed via kinetic study in aqueous solution at pH>7, which acts as a model catalyst for the decomposition of cumene hydroperoxide (ROOH) in Co²⁺+Phe+ROOH+H₂O system. The kinetic expression of a single catalytic decomposition reaction of ROOH under the influence of [CoPhe]⁺ complex, as well as the Arrhenius equation describing the temperature dependence of the effective constant K_eff (=K_cat[Co²⁺]₀[Phe]₀) of ROOH decay rate in the temperature range from 323 to 343 K are brought out.

A study of the interaction of methylene blue (MB) with poly(rA)-poly(rU) by the method of fluorescence spectroscopy has been carried out. The data obtained revealed that MB, being a DNA-specific ligand, can bind to double-stranded regions of RNA. In this regard, as in the case of DNA, semi-intercalation was the most preferable mechanism for the binding of this ligand to poly(rA)-poly(rU). On the other hand, non-linear curves of dependence of F₀/F on concentration of polynucleotide might result from two binding modes, the second of which was probably of an electrostatic nature. Proceeding from the data obtained, the value of K_SV was revealed to be almost an order of magnitude less than for DNA, which may indicate that RNA is a less preferable target for MB.

During ontogenesis, plants are exposed to various stress factors of biotic and abiotic nature. The nucleus and mitochondria are the most sensitive to ionizing radiation cell elements of all living organisms. The effect of ionizing radiation on the electrokinetic potential of isolated nuclei of wheat seedlings was studied, which allows us to judge the changes in the magnitude of the surface charge and its role in the functioning of the cellular nuclei. Changes were obtained in the values of the electrokinetic potential in isolated seedlings of irradiated seeds in a electric field. As a result of chain reactions, ionizing radiation changes the content of nuclear fractions, which in turn leads to a decrease in the surface charge and a decrease in the electromobility of nuclei.

In this work, the effect of millimeter range electromagnetic waves on the melting parameters of DNA complexes with ethidium bromide (EtBr) and Hoechst 33258 (H33258) has been studied. It has been shown that the millimeter wave irradiation of water-saline solutions of DNA complexes with ligands leads to significant changes in the water structure, which in turn results in relevant alteration of the thermodynamic characteristics of DNA–ligand complexes. It has also been shown that the irradiation of the water-saline solutions of DNA–H33258 complexes with millimeter waves of 64.5 GHz frequency results in the manifestation of the ligand specific interaction at the high ionic strengths, which is not observed in the absence of irradiation. With the millimeter wave irradiation, as a consequence of increasing of the degree of DNA hydration, the interaction mode of EtBr with DNA is non-specific to sequences, but the intercalation mode does not change.

Antibacterial and antioxidant activities of different extracts of saxicolous lichen Xanthoparmelia stenophylla sampled from Norashen, Gegharkunik Province of Armenia were studied. Methanol, ethanol and acetone extracts of lichen thalli were demonstrated to have activity against only tested gram-positive bacteria. Methanol extract of the lichen showed the highest amount of DPPH radical scavenging activity (~68%). Our studies did not reveal any significant antibacterial and antioxidant activities of aqueous extract.

Molecular hydrogen (H₂) and ethanol are the main by-products of glycerol fermentation by Escherichia coli. In this study, the growth of E. coli BW25113 was investigated with the addition of small amounts (0.05 to 2 %) of ethanol alone and in a combination with glycerol The bacterial growth, the kinetic of the redox potential, and the H₂ production in peptone medium, pH 7.5, were investigated upon various amounts of ethanol supplementation. In the presence of any amount of ethanol, but upon the absence of other sources of carbon, no H₂ production was observed. Whereas ethanol (0.3 to 1 %) with a combination of glycerol stimulated both bacterial growth and H₂ production, pH 7.5. A correlation was observed between the redox potential and stimulated by ethanol bacterial growth. The obtained results can be applied to regulate fermentation processes in biotechnology.

Molecular techniques, including denaturing gradient gel electrophoresis (DGGE), 16S rRNA genes clone library construction and metagenomic analysis, were used to describe the bacterial composition of the Karvachar geothermal spring. It was shown the predominance of bacteria belonging to the phyla Proteobacteria, Bacteroidetes, Firmicutes and Cyanobacteria in the studied spring. Representatives of phylum Firmicutes were not detected in the clone library, while DGGE profiling and metagenome analysis confirmed the presence of Firmicutes as one of the major components in the bacterial community.

A preliminary report is given on the comparative study of the level of psycho-emotional state of students studying at the “Quant” gymnasium and the State College of Fine Arts in different educational environments. The comparative analysis of the obtained data shows that creative work has a relaxing effect on mental tension, allows the individual to better adapt to life, allows for self-knowledge.

Soil salinization processes in the agricultural lands of Masis region, Armenia, were investigated. Soil samples collected from these areas at the beginning (April) and end (October) of irrigation season in 2019 were analyzed for electrical conductivity as an indication of salinity. The results of the study demonstrated that irrigation caused an intensive accumulation of soluble salts in the upper horizons of these agricultural soils posing a risk of a decline in soil productivity and of soil degradation. All of this calls for an urgent need for sustainable soil management in this region.

Seasonal hydrochemical, hydrophysical, and phytoplankton studies were conducted in a littoral zone of Lake Sevan in 2019. It is known that in recent years widespread algal blooms were usually started from the littoral zone of Big Sevan, and then spread towards the pelagic zone of the lake. The bloom was mainly caused by species belonging to the genus Dolichospermum (previously Anabaena). Our study has revealed that the physical and chemical properties of water were changed as a result of algal bloom. Particularly, the transparency of water and concentration of dissolved oxygen decreased, while the concentrations of ammonium, nitrite and phosphate ions increased. For the first time, the presence of the toxins microcystin and anatoxin-a was recorded in the lake.