Journal of the Serbian Chemical Society

N-2 Alkylated analogues of aza-galactofagomine as potential inhibitors of β-glucosidase

2024-05-29T19:00:35+02:00

The synthesis of four N-2-alkylated aza-galactofagomine (AGF) analogues was achieved by intermolecular reductive hydrazination or alkylation of suitably protected AGF. The synthesized compounds were evaluated as potential β-glucosidase inhibitors. The preliminary screening of inhibitor activity, conducted with sweet almond β-glucosidase immobilized in agar, as well as the standard inhibition assay with the same enzyme, showed the inhibitory potency of the synthesized analogues. In addition, these results are in a good agreement with the docking analysis of the human acid β-glucosidase, the enzyme implicated in Gaucher’s disease.

Molecular dynamics modelling of the structural, dynamic and dielectric properties of the LiF–ethylene carbonate energy storage system at various temperatures

2024-02-21T15:37:06+01:00

Lithium-ion batteries (LIBs) play a vital role in advancing the hybrid industry, especially in electric vehicles, as clean and sustainable electrochemical energy sources. However, the prevalent use of organic solvents in the liquid electrolytes of these energy storage systems raises environmental concerns. In this study, we investigated the impact of a polar aprotic solvent, ethylene carbonate (EC), on the structural, dynamic and dielectric properties of the LiF electrolyte using molecular dynamics simulations. By employing the CHARMM 36 force field, our goal was to comprehend the various physicochemical phenomena occurring in this electrolytic system across different temperatures within the saturation region. The structural properties were analyzed through the computation of the radial distribution function (RDF) for various pairs, while the dynamic and dielectric behaviors were elucidated by simulating the self-diffusion coefficient (D) and the dielectric constant (ε).

Joint characteristics and process parameters optimization on friction stir welding of AA 2024-T6 and AA 5083-H111 aluminum alloys

2023-11-23T09:25:42+01:00

Friction stir welding (FSW) is a recent method for welding in a solid-state environments. The FSW parameters, namely pin rotation speed, welding speed, axial force and tool tilt angle affect weld joint microstructure and tensile strength. The study optimizes process settings to enhance mechanical properties and uses Response surface methodology (RSM) to predict the ultimate tensile strength (UTS) of FS-welded AA 2024-T6 and AA 5083-H111. These parameters must be understood in order to get optimal mechanical qualities in manufacturing. The created model predicted tensile strength within 5 % of experimental data, helping optimize process parameters for FSW joints. Tool tilt angle affects heat, material flow, defect generation, welding force, and friction stir weld joint quality.

Characterization of enalapril maleate: An approach using thermoanalytical, thermokinetic and spectroscopic techniques

2024-02-01T10:47:30+01:00

Enalapril maleate is a widely used drug for the treatment of cardiovascular diseases. Its mechanism of action is to inhibit the angiotensin-converting enzyme selectively. Therefore, it is metabolized to enalaprilat by liver cells. The thermal behaviour of enalapril maleate was investigated by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), as well as with evolved gas analysis by simultaneous thermogravimetry and differential scanning calorimetry coupled infrared spectroscopy (TG-DSC–FTIR). The results provided information on thermal stability, purity, thermal decomposition steps and the main products formed in the heating. The enalapril maleate was found to be stable up to 148 °C. Above this temperature causes thermal degradation of the substance, which occurs in two stages in an inert atmosphere (N2) and three stages in an oxidizing atmosphere (air). Through the TG-DSC–FTIR the released gases were identified as maleic anhydride as a thermal decomposition intermediate. DSC analysis showed that the material obtained 99.5 % purity, which indicates high purity. Employing both the Kissinger and Friedman equations, alongside model fitting methods, the study reveals key insights. The Kissinger method unveils an apparent activation energy of 47.07±15.45 kJ mol^-1 for the complete thermal breakdown, a finding corroborated by the Friedman method. Model fitting methods, the article applies them, yielding an apparent activation energy of 55.7±3.4 kJ mol^-1 with a three-dimensional diffusion thermal degradation model.

Dispersive liquid–liquid microextraction for determining urinary muconic acid as benzene biological indicator

2024-03-08T01:12:51+01:00

The monitoring of occupational exposure to chemicals is essential for assessing the workplace. In the case of hazardous and carcinogenic chemicals, such as benzene, occupational monitoring becomes even more crucial. Trans,trans-muconic acid (t,t-MA) is one of the benzene urinary metabolites. Pretreatment methods for t,t-MA generally include liquid–liquid extraction and solid–phase extraction. Using dispersive liquid–liquid microextraction (DLLME) during sample preparation and extraction can reduce extraction costs and environmental impacts. Furthermore, the process is cost-effective and easy to operate. This study is aimed to develop, optimize, and validate an analytical method for measuring t,t-MA concentration in urine matrix through DLLME combined with high-performance liquid chromatography. In this method, five variables including pH, the volume of the extractant and the disperser, salt content and the time of centrifugation were optimized using the response surface methodology with a central composite design approach and experimental data. The proposed DLLME was successfully applied to real samples of exposed workers to benzene with extraction efficiencies from 95.8 to 102.4 %. The optimum conditions were pH 8, extractant solvent, 300 µL, disperser solvent, 300 µL, salt, 3.4 % and centrifuge, 3 min. According to the result of this study, the proposed DLLME approach can be effectively applied to the biomonitoring of individuals exposed to benzene.

Immobilization of periodate-oxidized horseradish peroxidase by adsorption on sepiolite

2024-05-15T07:30:21+02:00

Horseradish peroxidases (HRP), native and periodate-oxidized were immobilized onto sepiolite clay mineral by adsorption. Both peroxidases were adsorbed on this carrier in different quantities. Specific activity of immobilized enzymes was increased with increasing the amount of peroxidase added per gram of sepiolite. The highest specific activity was achieved when 15 mg of peroxidase was added per g of sepiolite. Also, periodate-oxidized enzymes showed similar specific activity as native ones. Stability studies (pH, thermal and operational stability) were conducted for both peroxidases. Residual specific activity of HRP immobilized onto sepiolite declined with an increase of incubation time at 65 °C. Oxidized-peroxidase lost 64 % of the initial activity, whereas native HRP dropped 92 % of its activity after 5 min of incubation at 65 °C. Reduction of the enzyme activity was observed with the temperature increase from 30 to 80 °C. pH profiles of native peroxidase immobilized onto sepiolite were higher in both acidic and basic regions compared to periodate-oxidized enzyme. Oxidized HRP was more successful in studies of operational stability, it retained 42 % of its activity after 4 consecutive cycles of pyrogallol oxidation, whereas native peroxidase kept only 11 % of the original activity.

Electrical, optical and structural characterization of interfaces containing poly(3-alkylthiophenes) (P3ATs) and polydiphenylamine on ITO/TiO2: Interaction between P3ATs polymeric segments and TiO2

2024-01-08T17:39:14+01:00

With the aim of studying the use of conjugated polymers poly(3-methylthiophene) (P3MT), poly(3-hexylthiophene) (P3HT) and polydiphenylamine (PDPA) in order to produce the active layer of inverted organic solar cells forming the interface with TiO₂ and also to help shed light on the optical and electronic properties applied to develop this technology, the interfaces between films containing P3MT, P3HT and PDPA on the indium tin oxide (ITO) electrode were electrochemically prepared, after chemically depositing a film of TiO₂. The systems under investigation were designated ITO/TiO₂/P3MT, ITO/TiO₂/PDPA/P3MT, ITO/TiO₂/PDPA, ITO/TiO₂/P3HT and ITO/TiO₂/PDPA/P3HT and characterized by Raman techniques (spectroscopy and microscopy), electrochemical impedance spectroscopy (EIS) and photoluminescence (PL). In this study, the aromatic, semiquinone and quinone segments in the polymer matrices of P3ATs and PDPA at these interfaces were monitored and characterized by comparison with films of their homopolymers by means of Raman spectroscopy and EIS. The Raman imaging demonstrates that the P3MT film can be incorporated into the titanium oxide crystalline lattice. The systems containing P3MT or P3HT were found to strongly interact with the TiO₂, stabilizing the P3AT radical cation segments and the presence of PDPA destabilized this interaction. These findings were complemented by the low-temperature (15 K) PL spectra, revealing a reduction in the intensity and displacement of the band associated with the radical cation emission, observed in the absence of TiO₂ in the system under investigation.

Mathematical approaches to a method of semiconductor materials films synthesis type AIIBVI for photosensitive structures used in alternative energy

2023-12-14T12:47:12+01:00

The scientific direction of the synthesis of CdS and CdSe thin films by the method of chemical surface deposition (CSD) using the aqueous solutions of cadmium-containing salts: chloride, nitrate, sulphate, acetate and iodide has been developed. A mathematical model of the CSD process of CdS and CdSe thin films was developed to improve the efficiency of experiments and reduce costs. The model makes it possible to determine the concentration of reagents, the duration, and the CSD temperature, which are necessary to obtain films of a specified thickness. The optimization of chemical deposition parameters of film-type semiconductor materials has been carried out. Based on the mathematical model, the optimal synthesis conditions were the following: the concentration of cadmium-source salt – 0.01 mol/L, chalcogenizer – 1.0 mol/L or 0.1 mol/L in the case of thiourea or sodium selenosulphate, respectively; the temperature: 70 °C and the duration of 3 min. The mathematical dependence of the experimental studies results of the metal ions content in thin-film solar cells for the effective direct conversion of solar radiation into electrical energy was proposed taking errors into account.

Synthesis of and theoretical research on some azine derivatives and investigation of their antimicrobial activities

2023-10-19T14:19:58+02:00

This study includes experimental, theoretical, and antimicrobial investigations on 1-(diphenylmethylene)-2-(4-methoxybenzylidene)hydrazine (5), 1-(3,5-dimethoxybenzylidene)-2-(diphenylmethylene)hydrazine (6) and 1-(diphenylmethylene)-2-(2,3,4-trimethoxybenzylidene)hydrazine (7). The structures of the compounds synthesized by microwave method were determined by spectroscopic methods and elemental analysis. Conformational analysis, ground state structure, fourier transform infrared spectra (FT-IR), and nuclear magnetic resonance (NMR) spectra of the compounds were computed using density functional theory (DFT) calculations in the theoretical research. Based on the B3LYP/6-31G(d,p) level, the conformers from the torsional barrier scanning were optimized. The B3LYP/6-311++G .(d,p) was used to determine the harmonic vibrational frequencies, potential energy distribution (PED), infrared intensities, and NMR chemical shifts of the most stable conformers. The experimental findings were compared with theoretically expected spectral data. The antibacterial activity of the prepared compounds was tested in vitro against nine bacteria and one yeast species. The antimicrobial activity of the compounds was tested by minimum inhibitory concentration (MIC) and agar well diffusion method. Compound 7 showed good activity against the bacteria and yeast, while 5 and 6 showed no antimicrobial activity. Compound 7 showed zone of inhibition values in the range of 10-15 mm against Klebsiella pneumonia, Pseudomonas aeruginosa and Salmonella typhimurium The results indicated that compound 7 was effective against bacteria.

Ultrasonic and spectroscopic investigations of molecular interactions in binary mixture of PEG-400 and DMSO at different temperatures

2024-05-02T11:55:20+02:00

In the present study, the ultrasonic velocity and density data for the binary mixture of polyethylene glycol (PEG)-400 and dimethyl sulfoxide (DMSO), at various concentrations and different temperatures (T, 288.15, 298.15 and 308.15 K), have been measured and further apllied to determine several physical parameters such as adiabatic and isothermal compressibility, intermolecular free length, internal pressure and free volume. The excess values of these parameters have also been computed and fitted with the Redlich–Kister (R–K) polynomial equation. The nature, type, and strength of intermolecular interactions present within the PEG-400 + DMSO mixture have been explained based on the sign and magnitude of excess values. Furthermore, partial molar volumes, excess partial molar volumes, apparent molar volumes and apparent molar volumes at infinite dilution have also been determined to investigate the solute–solvent interactions. Various mixing rules such as the ideal mixing rule (U_im), Nomoto relation (U_N), impedance dependence relation (U_Z), Junjie relation (U_J), van Deal–Vangeel relation (U_V) and collision factor theory (U_CFT) are employed to compute the ultrasonic velocity and compared with the experimental one. Among these relations, the Nomoto and Junjie relations are found to be most suitable for the given mixture. In addition to it, the present system has also been examined using Fourier transform infra-red (FTIR) and UV–Vis spectroscopic techniques. The change in intensity and shift in peak position in the FTIR and UV–Vis spectra of the PEG-400 + DMSO mixture are used to confirm the intermolecular hydrogen bonding in the given system.