Russian Chemical Bulletin最新文献

The possibility of introducing ruthenium ions into hydroxyapatite (HAP) with the formation of a HAP—Ru complex via the cocrystallization and sorption routes was shown. The morphology of the HAP—Ru composite depends on the Ru/Ca ratio when introducing ruthenium at a certain stage of the HAP synthesis. The time of reaching the maximum sorption is greatly affected by the synthesis method for HAP and its HAP—Ru complex. In the case of the precipitation and cocrystallization method, this time is 1 h, and when obtaining HAP by the enzymatic method (HAP_E) using alkaline phosphatase this time is 1 min. This is due to the significantly more developed external and internal surfaces of HAP_E. The sorption binding of ruthenium ions with HAP is almost irreversible. The introduction of ruthenium radionuclides (¹⁰⁶Ru as an example) into similar composites is possible both at the synthesis stage and during sorption, while the isotope exchange does not make a significant contribution to this process.

A series of new polyetherimides (PEIs) based on unsymmetrical 3,4′-(4,4′-(diphenyldioxy)diphthalic anhydride and a number of diamines were synthesized by single-stage high-temperature catalytic polycondensation in molten benzoic acid used as the so-called “active medium”. The chemical structure and phase morphology of the polycondensation products were studied by ¹H NMR and IR spectroscopies and by wide-angle X-ray scattering. The molecular weight characteristics were studied by viscometry and GPC methods. The synthesized PEIs are high-molecular-weight, film-forming, amorphous polymers that are soluble in organic solvents and possess good mechanical properties. The thermal properties of the synthesized PEIs were evaluated by DSC, TMA, and TGA methods. The polymers have high thermal and thermo-oxidative stability (> 500 °C), while their glass transition temperatures lie in the range of 220–300 °C depending on the diamine used in the synthesis. The rheological properties of melts were studied for a number of thermoplastic PEIs.

Studies of the catalytic activity of carbohydrases toward various polysaccharides and the data on the effect of the amino acid residues in the active site or in its vicinity on the activity of enzymes, their thermal stability, the pH optimum of the activity, and the susceptibility to inhibitors confirm the complexity of the spatial arrangement of their active site. The introduction of amino acid substitutions into carbohydrases made it possible to increase the activity of the enzymes, enhance the efficiency of polysaccharide hydrolysis, and increase the thermal stability of the enzymes and their resistance to inhibitors.

The effect of fluorene adsorption on the electronic and optical properties of graphene and MoS₂ monolayers was investigated. The fluorene—graphene and fluorene—molybdenum disulfide binding energies were estimated and the energy band structures and absorption coefficients were calculated using the density functional theory. Specific features of the atomic structure and physicochemical properties of the 2D layers after attachment of fluorene molecules are demonstrated.

Adsorption of poly(ionic liquid) (PIL) poly(1-ethyl-3-vinylimidazolium bromide) onto conductive surfaces was examined by quartz crystal microbalance with dissipation monitoring and atomic force microscopy. High surface coverage and the formation of continuous nanosized films were achieved by increasing the PIL concentration in the solution taken for adsorption of the polymer. The polymer-modified surfaces were used for subsequent electrostatic binding (adsorption) of glucose oxidase (GOx) as the model enzyme. The efficiency of the enzymatic reaction toward glucose for the prepared PIL—GOx thin films was evaluated by amperometry. The amperometric responses of the films correlate well with the efficiency of modification of the native surface by the polymer. Multiparameter physicochemical optimization of the adsorption of PIL and GOx made it possible to demonstrate the application potential of the polymer-enzyme thin films for highly sensitive analysis of glucose.

A new approach to evaluate the stability and integrity of a protein layer coating the surface of magnetic iron oxide nanoparticles (IONPs) in an aqueous medium was described using human serum albumin (HSA) as an example. The approach envisages investigation of the catalytic (peroxidase-like) activity of IONPs characterized by the generation rate of a colored product of o-phenylenediamine oxidation and examination of the capability of IONPs of binding to the plasma protein immunoglobulin G (IgG) to form submicron- and micron-sized aggregates. A correlation between the generation rate of hydroxyl radicals and the integrity of the HSA coating on the IONP surface (confirmed by experiments using IgG) was established for the first time. The approach developed belongs to the methods with a gentle impact on systems (non-damaging and low-damaging methods) for in situ and ex situ applications. The approach provides new possibilities for studying the physicochemical properties of hybrid nanosystems or submicron systems at various steps of their synthesis, as well as near physiological conditions, for example, in the blood plasma.

A convenient one-step synthesis of substituted 1,4-benzoxazepin-2-ones and 1,4-benzodiazepin-2-ones by recyclization of N-arylitaconimides with o-aminophenol and o-phenylenediamines. A detailed analysis of the spectral data of the synthesized compounds unambiguously confirmed the suggested structures. It was demonstrated that 1,4-benzoxazepin-2-ones are more conformationally flexible than 1,4-benzodiazepin-2-ones.

The analysis of the literature indicates a dual role of acetylcholinesterase (AChE) as an enzyme that hydrolyzes the neurotransmitter acetylcholine and simultaneously acts as a “pathological chaperone” promoting β-amyloid oligomerization. The review examines the interaction with AChE of several groups of neuroactive pharmacophore conjugates synthesized in our research group. A set of data obtained using the methods of enzyme kinetics, molecular docking, and fluorescence determination of the competitive displacement of the selective propidium ligand from the peripheral anionic site of AChE is analyzed. The results show the contribution of AChE as a bifunctional target to the neuroprotective potential of new multitarget compounds of various structural classes, allow us to explain the mechanism of the antiaggregatory activity of the conjugates while the original pharmacophores have no this activity, and provide ways to develop new cholinesterase inhibitors with a neuroprotective potential.

It was shown that sulfochlorination of isatins followed by reaction with amines and then with malonic acid derivatives is an efficient and highly efficient method for the synthesis of substituted oxindoles. The synthesis of a series of new 3-cyanomethyl- and 3-carboxymethyl-3-hydroxy-2-oxoindoline-5-sulfonamides was carried out, and their biological activity was evaluated in vitro for their effects on mitochondrial functions, lipid peroxidation, and the activity of recombinant human carbonic anhydrase II. It was found that the new compounds have weak antioxidant activity, do not affect mitochondrial membrane potential, and have low cytotoxicity towards human neuroblastoma SH-SY5Y cells. The effect of these compounds on intraocular pressure (IOP) was tested in experiments in vivo. A lead compound was identified that inhibited carbonic anhydrase II esterase activity with 99% efficiency at a concentration of 10 µmol L⁻¹, but no correlation was observed between inhibition of carbonic anhydrase II and IOP reduction. At the same time, compounds effectively reducing IOP in rabbits and rats were found. Simultaneously, it was shown that the antiglaucomatous effect of the compounds varies depending on the animal species.

Nicotinamide adenine dinucleotide (NAD⁺)-dependent formate dehydrogenase (EC 1.2.1.2, FDH) from methylotrophic bacterium Pseudomonas sp.101 (PseFDH) is the most stable enzyme among natural orthologs and is widely used in the synthesis of chiral compounds with NAD(P)⁺-dependent oxidoreductases. PseFDH is a homodimer and belongs to the subfamily of classic bacterial formate dehydrogenases with a polypeptide chain length of 400 amino acids. In the apo form of PseFDH and its complex with formate (PDB_2NAC and PDB_2GUG, respectively), only 374 residues are visible in each subunit, and in the structure of the holo form (PseFDH—NAD⁺—azide ternary complex, PDB_2NAD), 391 and 383 residues are visible in two subunits. The amino acid sequencing of PseFDH isolated from the original strain Pseudomonas sp. 101, showed that the subunit in this enzyme consists of 393 residues. We prepared the full-length recombinant PseFDH consisting of 400 residues and truncated mutants consisting of 393, 383, and 374 residues (PseFDH_400, PseFDH_393, PseFDH_383, and PseFDH_374, respectively) and studied their properties. Our results and analysis of the structure of the holo form of FDH from Moraxella sp.C1 (PDB_2GSD) indicate that shortening of the C-terminus of PseFDH during isolation from the natural strain and the presence of 391, 383, and 374 residue subunits in the crystals are caused by proteolysis.