Vol 23, No 4 (2023)

Thin-layer chromatography (TLC) has been used to study the infl uence of a number of factors (the nature of the stationary phase, the nature and concentration of the organic solvents and surfactants, the pH of the buff er solution) on the chromatographic characteristics of B vitamins: B1 (thiamine), B6 (pyridoxine), B12 (cyanocobalamin). The stationary phases were plates with polar (Sorbfi l on a polymer (highperformance plates, HTLC) and aluminum substrates), weakly polar (Polyamide-6), and nonpolar (RP-18 on an aluminum substrate) sorbents. As micellar mobile phases – micellar solutions of cetylpyridinium chloride in the concentration range 5–10-4 – 5–10-1 M, sodium dodecyl sulfate in the concentration range 2,5–10-4 – 5–10-1 М. It has been established that among aqueous-organic mobile phases (MF) the best results have been obtained for MF of the composition acetonitrile – water (15:385) on polar high-performance plates. More eff ective than acetonitrile – water is the PF of the composition acetonitrile – cetylpyridinium chloride (15:85) in the presence of a phosphate buff er solution with pH = 3. For the last PF, TLC determination of vitamins B1 , B6 , B12 in pharmaceutical preparations with a Sr value of interval 0.01–0.06 has been developed.

The method has been proposed for the spectrophotometric determination of antibiotics of the cephalosporin (cefuroxime, ceftriaxone, cefotaxime, cefazolin) and penicillin (amoxicillin) groups using chemometric data processing (method of partial least squares, PLS). The absorption spectra of 24 binary mixtures of “cephalosporin – cephalosporin” and 16 binary mixtures of “cephalosporin – amoxicillin” with various concentrations in the range of 3–27 and 5–140 μg/ml have been recorded. The optimal number of latent variables for each chemometric method (PLS-1 and PLS-2) has been selected, which ranged from 2 to 7 depending on the type of model and the nature of the antibiotics. The smallest root mean square calibration errors (RMSEC) have been found for the ceftriaxone–cefazolin system, which have been 0.09 and 0.08 for PLS-1 and PLS-2, respectively. The smallest root mean square errors of prediction (RMSEP) for the mixture “cefuroxime – amoxicillin” have been 0.07 for both methods (PLS-1 and PLS-2). It has been established that equations of linear relationships “measured-predicted” are characterized by a regression coeffi cient and the square of the approximation coeffi cient close to 1; which indicates the high quality of the models. The relative error of determination in test mixtures has been 0.4–6.2% by the PLS-1 method for “cephalosporin – cephalosporin” mixtures, and 0.07–6.0% by the PLS-2 method. At the same time, there is no signifi cant diff erence in the error in determining the components of the mixture, in contrast to the “cefuroxime – amoxicillin” system, for which the error is 0.1–1.1% for the fi rst component and 2.6–14.7% for the second component using the PLS-1 method and 0.2–1.2% for the fi rst component and 4.3–13.3% for the second component using the PLS-2 method. Thus, it has been shown that the use of chemometric methods ensures high accuracy of the spectrophotometric determination of the studied antibiotics with overlapping absorption bands in their mixtures.

Chitosan (CS) with a viscosity-average molecular weight of 200 kDa and a deacetylation degree of 82 mol%, produced by Bioprogress Ltd. (RF) has been used in this work. Aqueous solutions of enantiomeric salt complexes of CS with L- and D-aspartic acid (AspA) have been obtained at an equimolar CS:AspA ratio, in terms of amino groups. Powders of CS·L-(D-) AspA salts have been isolated from the corresponding solutions by evaporation of water and stored in a desiccator at zero humidity. It has been established that under such conditions a water-soluble salt form of the polymer with lamellar light beige particles 0.05–1.0 mm in size is formed. Using the methods of elemental analysis, IR and NMR spectroscopy, and X-ray diff ractometry, the chemical interaction of CS with L-(D-)AspA in aqueous solution and condensed state has been evaluated, and the chemical structure and supramolecular ordering of these enantiomeric salts have been studied. It has been established that, according to the classifi cation of K. Ogawa et al., the formula unit CS·L-(D-)AspA corresponds to non-hydrated salts of type I, in which water molecules are replaced by acid anions. IR spectroscopy confi rmed the donor--acceptor polymer–acid interaction and revealed a developed system of intermolecular and intramolecular contacts. One- and two-dimensional NMR spectroscopy showed the interaction of pairs of atomic nuclei between H3–H6 of the polymer and 2Hβ or Hα of the acid, H1 or H2 and Hα, H1 and H3–H6, due to the spatial proximity of protons in repeating monomer units, in the “bend” chain segments removed along the chain, and in neighboring macromolecules. For CS·L-AspA, additional resonances have been identifi ed between H2 and H3–H6 of the polymer, for CS·D-AspA these have been between H1 or H2. X-ray diff ractometry has revealed a highly ordered orientation of macrochains and a high crystallinity degree, untypical for CS salts. The salt complex CS·D-AspA, in contrast to CS·L-AspA, is characterized by a smaller amount of crystallization water, a more ordered supramolecular structure, and a more developed system of intermolecular and intramolecular contacts.

We performed a molecular genetic analysis of Yersinia pestis strains isolated in the Ural-Embensky desert natural plague focus area in the twentieth century. We studied 24 strains of Y. pestis isolated on this territory since 1945 to1991, as well as 21 strains of Y. pestis from adjacent territories. All of the strains studied from the Ural-Embensky natural focus of plague belonged to the highly virulent and epidemically signifi cant medieval biovar of the main subspecies Y. pestis. According to the results of the WG-SNP analysis and subsequent phylogenetic reconstruction based on 1353 SNPs, the maximum likelihood method (Maximum Likelihood, GTR model) revealed 6 key phylopopulations, which included strains isolated during diff erent periods of epidemic and epizootic activity in the study area. It has been established that there were three waves of spread of the 2.MED1 branch of the medieval biovar to the territory of Ural-Embensky desert natural plague focus. Strains isolated before 1945 belong to the fi rst wave of spread of the 2.MED1 branch to the territory of the Northern Caspian Region. The second wave is considered to be the 1968–1974 strains. They have close genetic similarities with strains from the Mangyshlak (1978) and Ustyurt desert plague foci (1962 and 1975). The third wave includes strains isolated after 1966. They are genetically close to the strains from the North Aral foci (1945). The data obtained will be used for molecular-genetic detailing of the certifi cation of foci in which this highly virulent medieval Y. pestis biovar circulates. They are important for determining the patterns of spatiotemporal distribution of highly virulent strains of the 2.MED1 branch of the medieval biovar in the 20th century and for long-term forecasting of the epizootic activity of plague foci in the North-Eastern Caspian region in the current 21st century.

The polytene chromosomes of the cells of the salivary glands of the larvae of Ch. plumosus L. 1758, Ch. entis Shobanov 1989, Ch. borokensis Kerkis et al. 1988 and Ch. curabilis Beljanina et al. 1990 from 20 reservoirs of six natural-territorial complexes of the Ural region were studied. On the basis of a cytotaxonomic study, it was established that natural complexes diff er from each other in the species composition of the “plumosus” group, the ratio (in %) between species and, certain parameters of cytogenetic variability of Ch. plumosus, Ch. entis and Ch. borokensis. Comparative analysis revealed diff erences between groups of natural complexes. A signifi cantly lower frequency of occurrence of sequence of chromosome disks pluA1.2 was found within the Ural plain-mountainous country (Western foothill and Middle Ural low-mountain regions) compared with natural complexes on the eastern slopes of the Southern Urals and the West Siberian Plain at the junction with the Ural mountain range. Populations of Ch. plumosus of the Ural plain-mountain country have lower cytogenetic distances between themselves compared to populations of Ch. plumosus on the eastern slopes of the Southern Urals and the West Siberian Plain at the junction with the Ural Mountain Range. With respect to Ch. entis, these territories diff er from each other in the absence of sequence of chromosome disks entА1.2 within the Ural plain-mountain country. According to cytogenetic distances, the populations of Ch. entis on the eastern slopes of the Southern Urals and the West Siberian Plain country at the junction with the Ural Mountain Range diff er more from the population of Ch. entis of the Ural plain-mountain country than among themselves. In the north-south direction, it is necessary to indicate a signifi cantly lower frequency of occurrence of sequence of chromosome disks borB1.2 within the Ural plain-mountain country (Eastern Podgorny region) relative to a natural complex with a more southern location within the West Siberian Plain country (Tura Plain region). For Ch. borokensis the interpopulation cytogenetic distances were calculated for the fi rst time (0.0128±0.0017). Diff erences in this indicator between the natural complexes of the Ural region have not been established.

The article refl ects data on year-round studies of the urban mallard population in Saratov, allowing the assessment of the condition and the study of the factors infl uencing its formation. An estimate of the mallard population in the winter periods of 2020–2023 is presented. It is shown that the number negatively correlates with frosts and precipitation, and there is a statistically signifi cant positive relationship between the number of people feeding ducks and the number of mallards. The state of the wintering and nesting population is assessed according to the index of synanthropization, the rate and path of penetration of the species into urbanized landscapes, and the stage of formation of the urban population in Saratov is determined. Adaptations of mallards to life in urban conditions and their impact on the ecology of the species as a whole are highlighted. The article emphasizes the need for further research on the impact of urbanization on mallard ecology and the benefi ts of this species for the urban ecosystem. The importance of monitoring population dynamics for its adaptation to the urban environment and maintaining the stability of the entire population is noted. In addition, the article provides a basis for further studies of the urban mallard population and can be a valuable source of information for the development of local programs for managing the available resources of ducks living in the park area of the city.