Objectives. Hypoxen is a drug which possesses antioxidant and antihypoxic effects. It achieves this by increasing the utilization of oxygen by mitochondria, intensifying oxidative phosphorylation, and as a result, improving tissue respiration. Athletes take it during prolonged exercise, in order to increase efficiency and reduce physical overwork. Since 2023, the World Anti-Doping Agency has included the drug in the monitoring program, in the belief that it can be used to gain a competitive advantage. It is thus a candidate for inclusion in the Prohibited List as a potential regulator of the human metabolism. Currently, there are no studies or scientific publications focusing on the identification of hypoxene in biofluids for the purpose of anti-doping control. The aim of this study is to determine the possible metabolites of the drug and their chromato-mass spectrometric characteristics in urine samples using gas chromatography–tandem mass spectrometry (GC–MS/MS) for doping control screening purposes.
Methods. Sample preparation of urine samples was carried out using enzymatic hydrolysis, liquid–liquid extraction and derivatization. The GC–MS/MS method was used for analysis. Screening of hypoxene metabolites was carried out in the mode of total ion current after fragmentation of selected parent ions.
Results. Three specific metabolites of hypoxene (m/z 342, 300, and 346, including trimethylsilyl derivatives) were identified in urine samples of volunteers (n = 3). They can act as markers for taking the target antihypoxant, and their possible structural formulas are given. The excretion curves of two metabolites with an m/z of 300 and 346 respectively in urine were studied. The maximum concentration is reached after 8–14 and 1.5–6 h, respectively. It was established, that these metabolites are reliably identified in urine 90 h or more after a single dose of the drug.
Conclusions. Possible structures of hypoxene metabolites in urine samples from volunteers were determined for the first time and their chromato-mass spectrometric characteristics were established. The approach developed in this study can be used for screening analysis of hypoxene for the purpose of anti-doping control.

Objectives. To study the substrate properties of Cy5-labeled deoxynucleoside triphosphates of various natures (dU and dC) in the process of incorporation in the DNA chain during recombinase polymerase amplification (RPA).
Methods. The work used the real-time RPA method. The method of horizontal electrophoresis was used to control the quality of the amplification products obtained.
Results. The influence of the fluorophore structure and linker lengths on the substrate properties for deoxynucleoside triphosphates Cy5-dUTP and Cy5-dCTP was studied. The following values of the substrate efficiency parameters were determined: amplification efficiency (kinetic indicator), normalized product yield, and embedding coefficient.
Conclusions. Modified deoxynucleoside triphosphates (dNTP) with long linkers between the fluorophore and the nitrogenous base, as well as between the quaternary ammonium group and the second heterocycle of the fluorophore, showed greater substrate efficiency than fluorescently labeled dNTP with short linkers. The modified dU in each pair demonstrated greater substrate efficiency compared to the modified dC.

Objectives. To isolate biosurfactants of glycolipid nature produced by oil hydrocarbon degrading bacteria and to establish their ability to solubilize hydrophobic compounds in the case of n-hexadecane.
Methods. Trehalolipids were isolated from bacteria Rhodococcus erythropolis X5 (VKM Ac-2532 D) and Rhodococcus erythropolis S67 (VKM Ac-2533 D) included in the MikroBak biopreparation for the bioremediation of oil-contaminated territories. The genome of R. erythropolis X5 is deposited in the National Center for Biotechnology Information database under GenBank accession numbers CP044283 and CP044284, BioSample – SAMN12818508, BioProject – PRJNA573614, and SRA – PRJNA573614. The content of trehalolipid biosurfactants was estimated by the amount of trehalose in aqueous solutions of biosurfactants using the phenolsulfur method. The surface tension of the obtained aqueous solutions of biosurfactants was determined by the du Noüy ring method using a Kruss K6 tensiometer (Kruss, Germany). The critical concentration of micelle formation was determined by the inflection point on the curves of surface tension dependence on the concentration of the biosurfactant solution. In order to establish the solubilizing ability of biosurfactants, the residual concentration of n-hexadecane in an aqueous sample of different concentrations was determined using a gas chromatographic method of analysis.
Results. At a constant surface tension of 24.2 mN/m and 25.0 mN/m for R. erythropolis X5 and R. erythropolis S67, respectively, the critical micelle concentration for both strains was 33 mg/L (3.8 ∙ 10⁻⁵ mol/L). The solubilizing effect of Rhodococcus trehalolipid micellar solutions against hydrophobic n-hexadecane was demonstrated by gas chromatographic analysis. The solubilization process was characterized using molar solubilization capacity (S_m), molar solubilization ratio (MSR), micelle–water partition coefficient (K_m), and solubilization energy 0 (ΔGS ). It was shown that the solubilization process of n-hexadecane proceeds spontaneously 0 (ΔGS = −35.5 kJ/mol) and more efficiently (S_m = 4.3 mol/mol, MSR = 4.7 mol/mol) than in comparison with other biosurfactants of glycolipid nature.
Conclusions. Based on the value of the molar solubilization coefficient, it can be concluded that trehalolipids of the R. erythropolis X5 strain solubilize n-hexadecane in aqueous solutions to a greater extent than compared to other biosurfactants of a glycolipid nature, but are inferior to synthetic surfactants.

Objectives. To investigate electrically conductive polymer composite materials (EPCMs) based on crystallizable polyolefins and electrically conductive carbon black for the production of self-regulating heaters; to study the mechanism of the occurrence of positive and negative temperature coefficients (PTC and NTC) upon heating such composites.
Methods. A comprehensive study of the structure and properties of crystallizable EPCMs with electrically conductive technical carbon was carried out. In order to measure the electrical characteristics of the composites, they were compacted into plates to model polymer heaters. Contact electrodes made of an ungreased brass mesh were embedded in their ends. The temperature dependencies of the electrical characteristics of the samples were investigated in a modified thermal chamber of an FWV 633.10 Vicat softening temperature meter. The change in the degree of crystallinity was analyzed by means of differential scanning calorimetry with a NETZSCH DSC 204 F1 Phoenix calorimeter. The dilatometric and rheological characteristics of the samples were studied using an IIRT-AM melt flow index tester.
Results. It was determined that the self-regulation ability (an abnormally high positive thermal coefficient of electrical resistance) of selfregulating heaters made of composites of crystallizable polyolefins with electrically conductive technical carbon cannot be explained by the thermal expansion of EPCMs alone. It was shown that in crystallizable polyolefin-based EPCMs, the inversion of the thermal coefficients of electrical resistance (transition from PTC to NTC) is associated with a change in the aggregate state of EPCMs and the beginning of its transition to a viscous-flow state. A mechanism involving a sharp increase in the electrical resistance of self-regulating crystallizable polyolefin-based composite with electrically conductive technical carbon was proposed and substantiated. This mechanism takes into account the additional shear deformation effect produced on the crystalline phase of the EPCM by numerous expanding melt microvolumes formed at the early stages of the melting process with a minimum change in the degree of crystallinity.

Objectives. To obtain polymer composite materials (PCM) with enhanced physicomechanical properties using the vacuum assisted resin transfer molding (VaRTM) method, binders must have a viscosity of up to 500 mPa∙s. In some cases, this leads to restrictions on the use of certain materials or requires the use of temporary diluents. This is closely related to the deterioration of other required composite characteristics, such as increased flammability. Three phosphorus-containing oligoester(meth)acrylates PhOEM-1, PhOEM-2, and PhOEM-3 were synthesized with significant differences in viscosity characteristics in the series PhOEM-1 << PhOEM-2 << PhOEM-3. The polymer based on PhOEM-1 exhibits inferior physicomechanical properties despite having lower viscosity. Hence, the aim of the study was to investigate the viscosity characteristics of mixtures of methacrylate binders of the same nature but different structures and functionalities. This was done by studying the rheological properties of the original oligoester(meth)acrylates and their mixtures taken in various ratios. The method used was to optimize compositions via a simplex lattice (Scheffe’s plan), in order to obtain PCM using the VaRTM technology.
Methods. The study of rheological properties of phosphorus-containing oligoester(meth)acrylates and their mixtures was conducted using the method of rotational viscometry on a Brookfield LVDV-II + Pro viscometer with a spindle 27 at different shear rates ranging from 0 to 70 s⁻¹ and temperatures from 30 to 70°C. Rheological studies were also conducted on a Lamy Rheology GT300 PLUS (GEL TIMER) viscometer in the same range of shear rates and temperatures.
Results. It was established that the objects under investigation can be characterized by viscosity values ranging from 96 to 2137 mPa∙s depending on the temperature. The nature of the viscous flow of phosphorus-containing oligoester(meth)acrylates and their mixtures is similar to that of Newtonian liquids only at certain shear rates. The effective activation energies of the viscous flow of binders and their mixtures were calculated, and the influence of temperature on the viscosity of binders was determined.
Conclusions. The study identified the features and nature of the flow curves of phosphorus-containing oligoester(meth)acrylate binders of the same nature but different structures and functionalities, as well as of their mixtures. The optimal composition ranges of threecomponent mixtures of phosphorus-containing oligoester(meth)acrylates for use in the VaRTM technological process in producing polymer composite materials within the temperature range of 30 to 70°C were defined. The optimal compositions and temperature conditions for obtaining polymer composite materials using the VaRTM technology were also identified. This enables the production of polymer products with complex geometric shapes and varying sizes.

Objectives. To study the transition of electrons in 1,2-phenyl(4’-carboxy)benzylidene Schiff base ligand and transition metal ions, optical properties, as well as the surface chemistry of supported transition metals using diffuse reflectance spectroscopy (DRS); to study the roughness and morphology of the Schiff base ligand and its complexes using atomic force microscopy (AFM).
Methods. DRS, AFM, and Fourier-transform infrared spectroscopy instruments were used to identify electron transitions, optical properties, and surface morphology in Schiff base ligands and their complexes.
Results. The DRS revealed the d–d transitions and charge transfer shifts of all compounds, and helped identify the structure of the ligand. One of the optical properties studied was the energy gap calculation of the ligand and its complexes. The copper complex exhibited more semiconducting behavior with surface morphology properties such as surface roughness parameters lower than those of the ligand and the cobalt complex. This can be attributed to the smaller size of the copper atom, as well as lower electron transitions compared to the cobalt complex and the square planar bonding shape.
Conclusions. In Schiff base ligands, the reflectance spectrum bands reveal three electron transitions: n→π*, π→π*, and σ→σ* transitions. In cobalt complexes, four transitions are indicated: 4A2(F)→4T1(F), 4A2(F)→4T1(P), charge transfer bands, and tetrahedral geometry. Copper complexes exhibit three transitions: 2B1g→2A1g, 2B1g→2Eg, and charge transfer bands, with a square planar geometry for their structure. The energy gap calculations were 2.42, 2.29, and 2.30 eV, respectively. In the case of the SH ligands, copper complexes, and cobalt complexes, all compounds exhibited semiconductor properties. However, the complexes displayed increased conductivity due to the influence of the metal and coordination structure.

Objectives. To determine the ion mobilities of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol; the structure of ions corresponding to characteristic signals; the detection limits of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol with the Kerber-T ion drift detector and the Segment automatic stationary gas detector.
Methods. Ion mobility spectrometry was used in order to determine the ion mobilities and detect analytes. The enthalpies of reactions of ion formation were calculated using the ORCA 4.1.1 software by means of the B3LYP density functional method with the 6-31G(d,p) basis set.
Results. The ion mobilities of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol were determined. A method for recording ion mobility spectra and their mathematical processing was developed. The dependencies of the change in ion mobility spectra on the analyte concentration were also studied. Possible mechanisms were proposed for the formation of the ion mobility spectra observed, in accordance with the ionization features of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol. The enthalpies of ion formation were calculated. The ionization schemes of the compounds were shown. The generalized results of experimental studies were presented, as were the features of compound identification taking into account the structure of the spectra, the concentrations of substances, and the detection conditions.
Conclusions. Characteristic signals of chloroacetophenone, tris(2-chloroethyl)amine, and methanethiol were identified. All studied hazardous substances can be detected with an ion mobility spectrometer at concentrations at the ppm level. The following detection limits of the substances were determined with the Segment gas detector: chloroacetophenone, 245 mg/m³; tris(2-chloroethyl)amine, 0.01 mg/m³; and methanethiol, 0.8 mg/m³.