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Proceedings of the National Academy of Sciences of Belarus, Chemical Series

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Vol 60, No 3 (2024)
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https://doi.org/10.29235/1561-8331-2024-60-3

PHYSICAL CHEMISTRY

183-191 1059
Abstract

A set of studies necessary to determine the suitability of a fibrous anion exchanger with ternary amino groups based on industrial polyacrylonitrile fiber Nitron C as a component of ion substrates was carried out. A laboratory-prepared ion exchanger sample had a working exchange capacity equal to 0.9 meq/g for the nitrate anion, which limits the biological productivity of the substrate for growing plants, in the physiological pH range = 5.5–7.5 and the concentration of the equilibrium nutrient solution is 0.02 eq/l. This capacity is at the level of the best granular ion exchangers and significantly exceeds the capacity of the previously used fibrous ion exchangers for growing plants in zero gravity conditions on space stations in 1970–1994 (Mir, Soyuz TM-10 – TM-17). The synthesized ion exchanger is a polyampholyte and contains three types of ion exchange groups, has high hydrophilicity and mechanical properties that allow it to be processed into textiles and used for any purpose, in which fibrous ion exchangers can be used (air and water purification, human protection means, etc.). 

192-202 1001
Abstract

New fibrous carboxyl cation exchangers FIBAN were synthesized by the method of graft copolymerization to polypropylene staple fibers of acrylic acid and various bifunctional comonomers (divinylbenzene – DVB, ethyleneglycoldimethacrylate – EGDM, methylene-bis-acrylamide – MBAA). Sorption properties of the fibers towards cations of heavy and non-ferrous metals (Cо2+, Ni2+, Zn2+, Cd2+, Cu2+ и Pb2+) were studied on the model solutions in the dynamic regime. The dynamic activity of the crosslinked sorbents towards Cu2+ and Pb2+ ions is higher compared to fibrous analogues FIBAN Х-1, FIBAN Х-2, FIBAN К-6М, FIBAN К-5, VION КN-1. The best sorbent for lead ions between the crosslinked fibers is the fiber with EGDM. The fiber with MBAA has a higher affinity towards the cations of Ni2+, Zn2+, Cd2+ and Cа2+, which increases with the increasing of the degree of crosslinking by MBAA. Studying the fibers by the methods of Fourier-transform IR-spectroscopy, scanning electron microscopy, analyzing of the chemical oxygen demand in water extracts and determination of the equivalent moisture capacity coefficient coefficient demonstrated that the crosslinking by MBAA provides a stable structure of the sorbent. The high stability of the crosslinked structure combined with the high ion exchange capacity near 7 mEq/g and dynamic activity towards the cations of Pb2+, Zn2+, Cd2+ и Cа2+ makes the fibrous carboxyl sorbent with MBAA safe and perspective for drinking water purification. 

COLLOIDAL CHEMISTRY

203-214 1010
Abstract

A detailed study of the supramolecular structure of high molecular weight resinous-asphaltene substances (RAS) and the study of their stability to thermal-oxidative degradation processes in the presence of surfactants is a promising scientific direction and can become the basis for the development of additional oil treatment processes and, as a result, the intensification of thermal transformations of oil dispersed systems (ODS). In the work it has been established that the maximum modifying effect, which consists in reducing the amount of asphaltenes by 8–11 % and increasing the concentration of resins, saturated and aromatic hydrocarbons in the composition of the dispersion medium, is achieved by the interaction of ODS with octadecylpropylenediamine, alkyldiamine with the content of ethoxylated groups n = 3–6 and butyl coconut fatty alcohol ester with n = 10. This fact is due to a change in the geometric parameters of asphaltene nanoaggregates due to the adsorption of these surfactants on their surface. Thus, against the background of an increase in the interplanar distances of condensed aromatic layers dm from 3.66 to 3.85 Å and values of the intrachain distance from 5.71 to 5.80 Å, the average diameter of aromatic layers decreases by 0.67–2.36 Å and the average height of their pack by 1.52–2.64 Å, while the average number of layers in a pack is 5. Estimation of the results of thermal analysis indicates that the RAS thermograms have a similar form with three endoeffects with minima in the ranges of ~ 34.7–37.7 °C (I); 325.7–339.3 (II) and 434.8–438.7 °С (III) and one exoeffect with a maximum of ~ 460.5–475.3 °С (IV). With a decrease in the factor of crystallinity and aromaticity of RAS, their resistance to the processes of thermo-oxidative degradation in the temperature region of coke formation increases. The energy of thermal-oxidative destruction for modified systems by surfactants exceeds by 21.6 kJ/mol of this indicator for unmodified RAS and is 62.07 ÷ 66.13 kJ/mol. 

ORGANIC CHEMISTRY

215-221 1090
Abstract

Optimal procedures have been developed for the synthesis of substituted isothiazoles containing an active chlorine atom in position 5 of the heterocycle and various functional groups in position 3: carboxyl, hydroxymethyl, aldehyde. Based on these methods, previously undescribed compounds were obtained: 5-morpholino-substituted 3-hydroxymethyl-4- chloroisothiazole, 4-chloroisothiazole-3-carboxylic acid and its methyl ester. The resulting substances are reactive building blocks for organic synthesis of compounds with a high potential for biological activity. 

BIOORGANIC CHEMISTRY

222-234 1014
Abstract

A liposomal (Lip) formulation of tissue plasminogen activator, alteplase (AlT), has been developed. The quantitative and qualitative composition of the liposomes, as well as their physicochemical properties and proteolytic activity, have been studied in relation to the thrombolytic liposomal form. It was determined that a formulation consisting of liposomes with a phosphatidylcholine/cholesterol ratio of 1.5 : 1, and lipids/alteplase ratio of 1 : 1, is optimal for treating acute myocardial infarction (AMI) in experimental models. At different component ratios, liposomes had a negative zeta potential value greater than 30 mV, indicating their aggregative stability, even after storage for two days at 20 degrees Celsius. Liposomes derived from soy phosphatidylcholine showed greater colloidal stability with a zeta potential of approximately –57 mV and a lower hydrodynamic diameter of approximately 140 nanometers, compared to liposomes derived from egg phosphatidylcholine, which had a zeta potential around –35.4 mV and a hydrodynamic diameter around 220 nanometers. The initial content of free AlT in the liposome supernatant from egg phosphatidylcholine (Lipeg) was 15.0 ± 4.0 %. During the incubation period of 4 days, the concentration of free AlT decreased to 9.0 ± 4.5 %. In contrast, in liposomes derived from soy phosphatidylcholine (LipS), the content of free AlT increased from 11.0 ± 4.5 % to 32.5 ± 6.0 % over the same incubation period. The value of the proteolytic activity of tissue plasminogen activator (tPA) in the compositions of Lipeg(AlT) and Lips (AlT) depends on the type of phosphatidylcholine. The initial tPA activity in Lipeg (AlT) was 36.0 %, and after 1 day, it increased to 45 %. In Lips (AlT), the initial activity was 61.0 % and increased to 66 % after 1 day. When using the liposomal form of alteplase for delivery into the coronary arteries of rats with acute myocardial infarction (AMI), a more complete fibrin lysis is noted compared to animals receiving the native form of the drug. The developed system of targeted delivery of alteplase using soy liposomes has been shown to significantly improve the degree of coronary artery lumen restoration by more than 15 %, compared to the use of a conventional drug (p < 0.05). 

235-245 1096
Abstract

CYP51 steroid-14α-demethylases are members of a large superfamily of cytochrome P450 enzymes found in all kingdoms of living organisms, and catalyze the 14α-demethylation reaction of a number of natural steroids, including lanosterol, obtusifoliol, and 24,25-dihydrolanosterol. CYP51 are important components of the eukaryotic steroid biosynthetic chain, and thus represent one of the main targets for antifungal therapy. A 14α-demethylase CYP51 homologous gene has also been found in the genome of Mycobacterium tuberculosis. At the same time, M. tuberculosis lacks the de novo pathway for steroid biosynthesis. Conservation of CYP51 among the Mycobacterium genus and colocalization in the genome with 3Fe-4S ferredoxin Rv0763c, which maintains its catalytic activity in vitro, may indirectly indicate the involvement of MTCYP51 in a biochemical process important for mycobacteria. In order to characterize the specificity of the MTCYP51 active site to various compounds of isoprenoid nature, we obtained a highly purified MTCYP51 and, using spectrophotometric titration and surface plasmon resonance methods, studied the interaction of MTCYP51 with steroids from marine organisms obtained in the Pacific Institute of Bioorganic Chemistry of the Far Eastern Branch of the Russian Academy of Sciences. The investigated compounds represent a wide range of evolutionarily ancient isoprenoids. The results showed that MTCYP51 is able to bind structurally diverse steroid derivatives in the active site. The conducted studies suggest the biological role of MTCYP51 for pathogenic mycobacteria, which consists in the binding and possible metabolism of exogenous bioregulatory isoprenoids in vivo. 

TECHNICAL CHEMISTRY AND CHEMICAL ENGINEERING

246-253 1051
Abstract

An IR spectroscopic analysis of the printing and technical properties of new types of multilayer packaging paper and cardboard containing waste polyacrylonitrile fiber and their interaction with printing inks was carried out. The preference for using multilayer composite paper and cardboard for the printing and paper industries is shown. It has been established that the tensile strength of paper does not depend on the strength of individual components, but on the strength of the paper structure formed during its production. When the paper contained 20% waste modified polyacrylonitrile, maximum optical density was achieved with a minimum thickness of the ink layer, that is, saturated prints were obtained with minimal consumption of printing ink.

254-264 1008
Abstract

The paper presents the results of studies on the production of semi-coated glazes with antibacterial activity by introducing variable valence oxides CeO2, WO3, Bi2O3, Fe2O3, MnO2 and MoO3 into their composition. The raw polycomponent compositions were comprised of aluminosilicate multi-calcium glass frit, dolomite powder, feldspar, alumina, quartz sand, wet-enriched kaolin and refractory clay. The coatings were obtained by single firing on a ceramic-based porcelain stoneware at a temperature of 1 200 ± 5 °C in a high-speed mode for 60 ± 2 minutes. The study focused on the processes of glaze formation of coatings and the influence of the components of glaze charges on decorative and aesthetic characteristics of coatings (color, texture, gloss and whiteness). Parameters of physical and chemical properties were determined in accordance with the existing specification for the products, i. e. temperature coefficient of linear expansion, heat resistance, chemical resistance, microhardness, frost resistance, wear resistance, etc. Antibacterial activity of the coatings towards Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538 test strains was studied. 



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ISSN 1561-8331 (Print)
ISSN 2524-2342 (Online)