Vol. 51 No. 1 (242) (2017)

The analysis of fluorescence 2D and 3D spectra of tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) measured in physiological solution at 293 K are presented. The spectral characteristics of 2D fluorescence spectra of amino acids (AAc) are recorded in the following conditions: for Trp λ_ex/λ_em=280/357, for Tyr 275/303 and for Phe 257/283 nm, and the 3D spectra of AAc recorded in λ_ex=200–450 and λ_em=200–500 nm ranges are given. It has been revealed that 3D spectra of AAc are characterized by two strong excitation/emission peaks located at λ_ex/λ_em=230/350 and 280/350 nm. The high energy emission (absorption) at 230 nm is due to n→π^* or π→π^* transitions of the carboxylic or amide group and low energy emission (absorption) at 280 nm is due to π→π^* transition in the indole ring. In 3D spectra Rayleigh scattering peak and second-order scattering peak are identified as well.

By esterification reaction of 1,2,3,4-tetrachlorobutane with salts of stearic, palmitic and oleic acids corresponding erythritol esters are obtained. The effective methodology for esterification reaction at temperatures 100–190^oС with or without solvents is worked out. The physical and chemical constants of the obtained compounds are defined.

The water quality of the Rivers Vorotan, Sisian and Goris was evaluated by Armenian Water Quality Index (AWQI) for the first time. The increase of the value of AWQI was shown, which indicates a decline of the water quality in the Rivers. Some correlation between AWQI and other indecies estimating water quality is established.

The sorption capacities of two peat samples were determined with AAS method. The first one is a natural peat and the second sample is modified with chitosan. The peat was used, was from fields of Vardenis (Gegharkunik Marz of RA). To evaluate the sorption capacity of the sorbents the models of Langmuir and Freundlich were applied. Application of chitosan to the surface of the peat was performed by 3% chitosan solution acidified with citric acid solution. The cross linking was performed by formaldehyde. Sorption processes carried out in static mode.

The in vivo influence of antitumor drug cisplatin on content of phospholipids and neutral lipids in chromatin fraction on rat brain cells was investigated. It was shown, that the drug action leads to decrease in total phospholipids and neutral lipids content about 24 and 20% correspondingly. In spite of these significant changes of total lipids, the alterations in relative quantities and percentage of individual phospholipids as well as neutral lipids in chromatin were negligible. These results indicate that cisplatin excites universal changes in lipid metabolism in chromatin appreciably reducing the absolute quantities of all individual phospholipid and neutral lipid fractions available in chromatin preparations. The significance of these quantitative changes in development of cisplatin antitumor effects was discussed.

Comparative study of DNA complexes with acridine orange (AO), ethidium bromide (EtBr) and methylene blue (MB) has been carried out at 0.02 M ionic strength of solution in 0 < r $\leq$ 0.33, r = [ligand] / [DNA] range. The values of changes of melting parameters ($\delta(1/T_m)$ and $\delta(\Delta T/T_m^ 2))$ of these complexes were determined. From the obtained data it was revealed that the dependence of $\delta (1/T_m)$ enhances in the whole interval of change of r for three ligands, while the dependence of $\delta(\Delta T/T_m^ 2)$ rises at relatively low values of r and comes out to plateau in the case of AO and MB; in the case of EtBr this dependence takes bell-like form.

The influence of electromagnetic irradiation by extremely high frequencies 41.8 GHz and 51.8 GHz (EMI EHF) on chemiluminescence (H₂O₂–Cl) intensity, malondialdehyde (MDA) content and catalase activity in wheat shoots cells has been investigated. It has been shown that this irradiation impacts on lipids oxidation of cellular membranes of plant seedlings and leads to intensity increasing of freeradical processes, measured by CL. It has also been shown that at multiple irradiation of wheat seedlings the increasing of MDA rate is observed. At the same time EMI-induced oxidative stress was indicated by markedly change of catalase activity depending on EMI frequency used and exposure duration.

The interaction of ethidium bromide (EtBr) with polyinosine (poly(I)) has been studied by absorption and fluorescence spectroscopy methods. Our investigations have shown that titration experiments within raising of poly(I) concentration the maximum of absorption in visible region decreases and is shifted toward longer wavelength region. According to the obtained results it is assumed that poly(I) in physiological conditions exists both in single- and double-stranded helices formed contemporaneously. The studies are relevant to understand the polyinosine structure in aqueous-salt solution.

Nowadays, in the era of widespread antibiotic resistance, plants are considered as one of most prospective sources for new antimicrobial compounds. The goal of our research was to screen the antimicrobial efficiency of 48 plant parts of 28 wild plants species, which are commonly used in Armenian folk medicine. Maceration technique was used to obtain plant crude extracts. Antimicrobial activity of plant materials was evaluated by agar well diffusion assay against five bacterial and two yeast strains. Agrimonia eupatoria, Hypericum alpestre, Lilium armenum, Sanguisorba officinalis and Rumex obtusifolius expressed the highest and broadest antimicrobial activity against tested strains and they were selected for further comprehensive studies.

The influence of synthetic amino acids and peptides on the growth of Pseudomonas aeruginosa multidrug resistant strains isolated from soil has been studied. All investigated strains were sensitive to (S)-β-[4-allyl-3-(furan-2-yl)-5- -thioxo-1,2,4-triasol-1-yl]-α-alanine, (S)-β-[4-allyl-3-(2’-chlorophenyl)-5-thioxo-1,2,4-triazol-1-yl]-α-alanine, dipeptide N-formyl-methionyl-(S)-β-[4-allyl-3-(2’-chlorophenyl)-5-thioxo-1,2,4-triasol-1-yl]-α-alanine and tripeptide alanyl-glycyl-(S)-β-[4-allyl-3-(pyridin-4’-yl)-5-thioxo-1,2,4-triasol-1-yl]-α-alanine. Dipeptide alanyl-(S)-β-[4-allyl-3-(pyridin-4’-yl)-5-thioxo-1,2,4-triazol-1-yl]-α-alanine demonstrates the strongest effect on the growth of P. aeruginosa strains 9311 (resistant to beta-lactams) and 9211 (resistant to beta-lactams and chloramphenicol), but has no influence on the P. aeruginosa 5249 (resistant to all antibiotics used in this study).

The computerized database of mycorrhizal fungi, which includes detailed information about 211 mycorrhizal species of the RA was created. The database allows for use this information for scientific and practical purposes

Hortun-1 is one of the richest fossil floras of Armenia and dates from Early Pliocene (Early Akchagil). The studied material includes more than 2100 samples kept in the Institute of Botany of NAS RA, in the Palaeobotanical storage. As a result of the study, 4 imprints of leaves of Brassaiopsis mirabilis Kol. were determined, which were the first brought for the fossil floras of Hortun and for the whole Armenia. Samples give an opportunity to make a conclusion on climate change.