Moscow University Chemistry Bulletin最新文献

Matrix solid-phase dispersion using a humate-based magnetic sorbent is proposed as an efficient method for the concentration of bisphenol A from fish muscular and hepatic tissue samples followed by the chromatography-mass spectrometry determination of an analyte prederivatized with acetic anhydride. Under the optimum concentration conditions (the stirring time is 10 min and the sorbent weight is 0.05 g), the recovery of bisphenol A upon single sorption reaches 85%. The percentage desorption exceeds 99% (the eluate is methanol, the time is 3 min, and the volume is 1 mL). The maximum enrichment factor is 718. The limit of the detection of bisphenol A is 0.15 μg/kg (on a dry basis) for muscular tissue and 0.25 μg/kg for liver.

Hybrid nanoforms based on silver and the antibacterial drug dioxidine (2,3-bis-(hydroxymethyl)quinoxaline 1,4-di-N-oxide) are prepared by the method of joint cocondensation of metal and ligand vapors on a liquid nitrogen-cooled surface. The samples obtained are characterized by FTIR-, UV-Vis, and XPS-spectroscopy, as well as ТЕМ, SEM, and powder X-ray phase analysis (ХРА). It is shown that cryomodified nanoforms preferably consist of the anhydrous triclinic (T-phase) crystal phase of dioxidine. The dimensions of dioxidine particles ranged from 50 to 300 nm and the average size of doping silver nanoparticles is 15 ± 3 nm. The broadening of the diffraction patterns belonging to silver shows the transition of metallic silver to the nanoscale state. The FTIR results indicate hybrid nanoforms stabilized by the donor-acceptor interactions of surface silver atoms with the hydroxyl groups and with the donor N-atoms of quinoxaline cycles of dioxidine molecules.

N-Acetylaspartylglutamate (NAAG) is the most common dipeptide in brain cells, which is synthesized using the enzyme N-acetylaspartylglutamate synthase. In this study, we utilize bioinformatics methods to predict the protein structure based on the primary sequence of the coding gene, classical molecular dynamics to obtain a stable protein complex with N-acetylaspartate and glutamate ligands within the trajectory, and machine learning methods to analyze, describe, and select potential reactive and nonreactive conformations of the model system describing the enzyme–substrate complex. Molecular dynamics trajectories are obtained for a set of selected conformations within the framework of the method of combined quantum and classical molecular mechanics, and the active site of the protein–ligand complex and potential reaction mechanism are characterized.

The configurations of small copper clusters (Cu₂, Cu₃, Cu₁₃) and their complexes including a complex containing a copper atom with dioxidine (Dx) are calculated by density functional theory modeling with B3LYP5 parametrization. The trends of the changes in the geometry configuration and metal cluster–dioxidine ligand interaction energy depending on the size of the metal cluster are assessed. The dissociation energy of the complexes increases with the metal cluster size but the maximum value (55.1 kcal/mol) is implemented for a Cu₃–Dx complex. There is coordination of the metal atom to one or two oxygen atoms of the dioxidine molecule for all the complexes.

The technological scheme of cesium extraction from spent fuel before hydrometallurgical reprocessing is developing in order to reduce the heat dissipation and specific activity of spent fuel. The scheme includes the joint high temperature treatment of spent fuel and molybdenum trioxide, flushing the product with an alkali solution to remove cesium, and then dissolving the fuel in nitric acid. Implementation of this technology will allow reducing the cooling time of the spent fuel and reduce the radiation impact on personnel, equipment, and technological environment. This article presents the results of the experimental substantiation of the choice of temperature of the high-temperature treatment, comparative analysis of the efficiency of flushing solutions of different compositions, and determining the duration of the cesium fractionation process. The research was conducted in laboratory conditions with the use of spent fuel imitators and radionuclide markers.

Photoregulated adenylate cyclases bPAC and OaPAC are compared using methods of classical molecular dynamics in the states before and after irradiation with light. The pathways of signal transduction from the photoreceptor domain to the catalytic domain are determined. The more pronounced acceleration of the catalytic reaction as a result of irradiation with light in the case of bPAC is determined both by a shift of the equilibrium towards a closed conformation and a more significant increase in the number of suboptimal pathways of allosteric signal transduction from one domain to another.

A nondestructive analysis of tetracyclines in drugs by their own fluorescence using a smartphone and a device printed on a 3D printer is proposed. The possibility of using chemometric methods, which reduce the analysis time and visualize the obtained data, is shown. The dataset is processed by principal component analysis (PCA), hierarchical cluster analysis (HCA), partial least squares (PLS) regression, and least squares using the PhotoMetrix PRO^® software. The use of chemometric methods of analysis to determine the concentration of the active substance and identify the manufacturer of medicinal products is considered.

This article succinctly outlines the key points of the emergence and development of methods for chemical modification of the surface of inorganic substrates. It is shown that the assumption of the presence of chemically active functional groups on such surfaces arose relatively recently, although the first experience of practical application was carried out in the middle of the 19th century. The main stages in the development of the chemistry of surface compounds are traced.

This review is devoted to the consideration of pathological intracellular mechanisms characteristic of Huntington’s disease and the central role of huntingtin protein in these processes. The features of mutant huntingtin aggregates utilization by the ubiquitin–proteasome system and autophagy, as well as the possibilities of polyglutamine-containing substrates hydrolysis by proteasome are discussed.

Biopolymer materials based on natural collagen (gelatin, hydrolyzed collagen) are widely used in the food, pharmaceutical, and cosmetic industries due to their low toxicity, high biocompatibility, low antigenicity, and unique mechanical and technological properties. Hydrolyzed collagen, unlike gelatin, is formed by peptides with a lower molecular weight. Its advantages are higher bioavailability and biodegradability in comparison with gelatin. In this study, biopolymer matrices containing a dioxidine antibacterial drug are obtained based on hydrolyzed collagen using low-temperature technologies. It is shown that, varying synthesis parameters such as the concentration of hydrolyzed collagen in the precursor solution (from 1 to 10%), matrix crosslinking time (0.1–24 h), and cryoforming temperature (–30 and –196°C), it is possible to change the morphology and structure of the matrix, its degradation time, and drug release time. The composition and structure of dioxidine/hydrolyzed collagen systems are characterized by SEM and IR and UV spectroscopy. The antibacterial activity of the resulting dioxidine/hydrolyzed collagen systems against E. coli and S. aureus is characterized by the disk diffusion method.