Moscow University Chemistry Bulletin最新文献

Technology and equipment are developed for purifying low-pressure gas flows from hydrogen sulfide and mercaptan contaminants. The efficiency of the catalytic desulphurization up to a residual content of sulfur-containing compounds of (SH) < 10 ppm is demonstrated using the example of model mixtures of a low-pressure gas in a disk film apparatus. The prospects for the creation of desulphurization units for the recovery of oil-loading vapors with the production of commercial quality hydrocarbons, as well as for the purification of atmospheric emissions from sulfur-containing ecotoxicants and hydrocarbons, during the oil loading processes are considered.

The resolved vibrational structure of a UV absorption spectrum of the molecule in the gas phase is obtained. The (0–0) bands of the isomers are found. The fundamental vibrational frequencies and (0–v) torsional vibration transitions for the s-trans and s-cis isomers of the molecule are found in the ground (S₀) and excited (S₁) electronic states. The 68 absorption bands are assigned completely.

This review is devoted to the development, properties, and application of biosensors based on graphene nanomaterials. It is shown that such biosensors are characterized by their sensitivity, specificity of detection of analytes, high speed, and small size. Examples of the use of graphene biosensors for the detection of viruses, bacteria, markers of socially significant diseases, and various toxins are given.

NAD⁺-dependent formate dehydrogenase (FDH, EC 1.2.1.2) from bacterium Staphylococcus aureus (SauFDH) is the most active enzyme among FDHs of this group; however, the high values of K_M of the enzyme with NAD⁺ and formate in the standard 0.1 M phosphate buffer result in lower catalytic efficiency k_cat/K_M than for other FDHs. Here, we study the effect of different buffers on the catalytic properties of SauFDH. Sodium phosphate (NaPB) is used as the base buffer component and Tris, Gly and citrate (Cit) are added to NaPB to prepare double, ternary, and quaternary buffer systems with different concentrations. It is found that K_M for formate does not depend on the buffer composition and concentration, while the values of k_cat and (K_{{text{M}}}^{{{text{NA}}{{{text{D}}}^{{text{ + }}}}}}) increase and decrease significantly. The highest positive effect is achieved in the case of quaternary buffer NaPB-Cit-Tris-Gly. At a 0.05 M concentration of each component, k_cat increases by 70% compared to one in the standard 0.1 M NaPB. At a 0.1 M of each component, improvement in both parameters, k_cat and (K_{{text{M}}}^{{{text{NA}}{{{text{D}}}^{{text{ + }}}}}}), is observed. Thermal inactivation studies in NaPB and the complex NaPB-Cit-Tris-Gly buffer showed that at component concentrations of 0.1 M and more, SauFDH’s thermal stability increased. The value of the stabilization effect depends on the ion strength but not on the type of buffer. A comparison of the X-ray structures of holo-forms of SauFDH and FDH from bacterium Pseudomonas sp.101 shows that the active site of PseFDH in complex with the substrate is totally closed, while in holo-SauFDH, amino acid residues in the active site can be accessed by water molecules and buffer components. This could be the reason of the k_cat and (K_{{text{M}}}^{{{text{NA}}{{{text{D}}}^{{text{ + }}}}}}) changes in buffers of different compositions.

Phenylacetone monooxygenase from Thermobifida fusca (EC 1.14.13.92, PAMO) belongs to the Baeyer–Villiger family of monooxygenases and catalyzes the oxidation of various aromatic ketones to the corresponding esters using NADPH as a cofactor. In this study we analyzed the structure of the cofactor binding site, selected the most important amino acid residues for recognition of the phosphate group of the cofactor, and simulated enzyme structures with amino acid substitutions that could potentially lead to a change in the coenzyme specificity of the enzyme from NADPH to NADH. Based on the modeling, the most promising amino acid substitutions, T218D, T218E, K336A, and K336R, were proposed. Using site-directed mutagenesis we obtained genetic constructs containing genes encoding PAMOs with the corresponding amino acid substitutions, and the enzymes were expressed and purified. The resulting mutant PAMOs are able to bind NADH, but lack the ability to catalyze the oxidation of benzylacetone in the presence of NADH and show a deterioration of the Michaelis constants for NADPH. The catalytic constants of the mutant enzymes studied decrease slightly, and remain within the allowed experimental error.

Flavonoids are polyphenolic compounds having benzo-ɤ-pyrone structures, which are majorly available in plants. Several flavonoids have been reported, which are responsible for the colors of the flower, fruits, and leaves. They have several biological activities. These flavonoids belong to plant secondary metabolites and are mainly classified into various classes, based on molecular skeleton such as flavonols, flavones, flavanones, isoflavones, anthocyanidins, aurones, and chalcones. Among them, flavones gaining tremendous importance due to their wide biological importance and their potential clinical uses. These flavones commonly exist in a variety of spices, fruits, and vegetables. Anticancer activity, antioxidant, and anti-tubercular activity of flavones are now reviewed based on the recent literature from 2015–2020.

The boron-doped diamond electrode has been widely applied in electrochemical process for wastewater treatment based on the generation of hydroxyl radicals (^•OH). This study investigated the formation efficiency of 2-HTA through the interaction between ^•OH radical and terephthalic acid (TA) to monitor the ^•OH formation. Results show that the 2-HTA formation efficiency did not depend on the initial concentration of scavenger (here, TA) in the investigated range of 0.1 to 1 mM TA. Meanwhile, other factors, such as current density, supporting electrolyte, sodium hydroxide have a significant influence. The optimal condition was established: concentration of electrolyte (0.05 M Na₂SO₄); initial concentration of TA (0.1 mM); concentration of NaOH (1 mM); current density (j = 20 mA cm^–2). The selectivity of TA was evaluated by Faradaic efficiency (η) and hydroxylation yield (({{{{gamma }}}_{{{text{TAOH}}}}})), indicating that Faradaic efficiency (η) for 2-HTA formation was in the range of 10^–5–10^–7, while the hydroxylation yield of ^•OH (({{{{gamma }}}_{{{text{TAOH}}}}})) into 2-HTA was 0.03–0.12.

In this paper, we describe the synthesis of cationic amphiphiles based on aliphatic and aromatic amino acids and diethanolamine derivatives. The calculation of the hydrophilic-lipophilic balance for a number of structures makes it possible to identify the structures with potential antimicrobial activity against gram-positive and gram-negative bacterial strains. The schemes for the synthesis of mono/bivalent cationic lipoamino acids and lipopeptides are developed. Two series of amphiphiles are obtained in preparative quantities for subsequent microbiological studies and determining the minimum inhibitory concentration.

The methods of real-time PCR and digital droplet PCR are compared to determine mutations in the promoter region of the TERT gene with different systems of detection probes. The mutations’ detection limits for these methods are determined and the advantage of the digital droplet PCR method for the analysis of the central nervous system’s (CNS’s) tumor lesions is shown. The mutant allelic fraction of changes in the TERT gene promoter for the genomic DNA of cell cultures of the human brain’s tumors, which amounts to 60% for Grade IV glioblastoma IDH1, is analyzed for the first time. To compare methods, a versatile system based on recombinant plasmids, which turns out to be better than the system based on genomic DNA cell lines, is proposed.

A structural rheological model is presented that describes the phenomenon of shear solidification in structured systems, namely, in concentrated suspensions, micellar solutions, and solutions of associated polymers. The reason for shear hardening (SH) is the appearance of a structure under the action of shear as a result of an increase in the cohesion force between particles or macromolecules. The integral characteristic of the structure is the total number of particles in the aggregates. The kinetic equation describing the process of formation-destruction of aggregates contains four rate constants and leads to a rheological equation with two coefficients.