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Abstract

The paper describes synthesis and testing of novel biodegradable polylactide-based polymer membranes with desired mechanical properties, which are capable of sustained and directed release of biomacromolecules with high molecular weight (in particular, streptokinase; m.w. 47 kDa). Streptokinase is a pharmaceutical agent, possessing a pronounced thrombolytic activity. The membranes synthesized had a percentage elongation of 2–11% and tensile strength of 25–85 MPa. They were biodegradable – yet being stored in aqueous media in the absence of biological objects, would be dissolved by no more than 10% in 6 months. The synthesized membranes were capable of controlled release of streptokinase into the intercellular space, with the enzyme retaining more than 90% of its initial activity. The rate of streptokinase release from the membranes varied from 0.01 to 0.04 mg/day per cm2 of membrane surface. The membrane samples tested in the work did not have any short-term toxic effects on the cells growing de novo on the membrane surface. The mitotic index of those cells was approximately 1.5%, and the number of non-viable cells on the surface of the polymer films did not exceed 3–4% of their total amount. The implantation of the synthesized polymers – as both individual films and coatings of nitinol stents – was not accompanied by any postoperative complications. The subsequent histological examination revealed no abnormalities. Two months after the implantation of polymer films, only traces of polylactide were found in the implant-surrounding tissues. The implantation of stents coated with streptokinase-containing polymers resulted in the formation of a mature and thick connective-tissue capsules. Thus, the polylactide membranes synthesized and tested in this work are biodegradable, possess the necessary mechanical properties and are capable of sustained and directed release of streptokinase macromolecules.

Abstract

Modern high-temperature technologies and methods of production of advanced materials impose new requirements on the quality of information on physicochemical properties of oxide systems at high temperatures. Normally, thermodynamic approach for these purposes is the most fundamental and essential. Great attention was paid by M.M. Shultz to extensive development of this approach in the studies of oxide melts, crystals, glasses, ceramics, and coatings using calorimetric, EMF, and high temperature mass spectrometric methods. Advantages of the thermodynamic approach were illustrated by examples of application of the Knudsen effusion mass spectrometric method to studies of oxide systems and materials, which were crucial for the further development of space and aviation industry, energetics, instrument making, communication engineering, metallurgy, energy-saving, and environmental safety. In the discussion of the regularities of vaporization processes and changes of thermodynamic properties in oxide systems, a number of particular systems based on silica and hafnia was considered in detail. Modeling was carried out for these systems using the Generalized Lattice Theory of Associated Solutions. The obtained results assert a necessity for creation of the national thermodynamic data- and model bases essential for further prediction of phase equilibria in oxide systems and materials at high temperatures.

Abstract

Nowadays, hydrogen has become not only an extremely important chemical product but also a promising clean energy carrier for replacing fossil fuels. Production of molecular H2 through electrochemical hydrogen evolution reactions is crucial for the development of clean-energy technologies. The development of economically viable and efficient H2 production/oxidation catalysts is a key step in the creation of H2-based renewable energy infrastructure. Intrinsic limitations of both natural enzymes and synthetic materials have led researchers to explore enzyme-induced catalysts to realize a high current density at a low overpotential. In recent times, highly active widespread numerous electrocatalysts, both homogeneous or heterogeneous (immobilized on the electrode), such as transition metal complexes, heteroatom- or metal-doped nanocarbons, metal-organic frameworks, and other metal derivatives (calix [4] resorcinols, pectates, etc.), which are, to one extent or another, structural or functional analogs of hydrogenases, have been extensively studied as alternatives for Pt-based catalysts, demonstrating prospects for the development of a “hydrogen economy”. This mini-review generalizes some achievements in the field of development of new electrocatalysts for H2 production/oxidation and their application for fuel cells, mainly focuses on the consideration of the catalytic activity of M[P2N2]2 2+ (M = Ni, Fe) complexes and other nickel structures which have been recently obtained.

Abstract

The rapid development of additive technologies in recent years is accompanied by their intensive introduction into various fields of science and related technologies, including analytical chemistry. The use of 3D printing in analytical instrumentation, in particular, for making prototypes of new equipment and manufacturing parts having complex internal spatial configuration, has been proved as exceptionally effective. Additional opportunities for the widespread introduction of 3D printing technologies are associated with the development of new optically transparent, current- and thermo-conductive materials, various composite materials with desired properties, as well as possibilities for printing with the simultaneous combination of several materials in one product. This review will focus on the application of 3D printing for production of new advanced analytical devices, such as compact chromatographic columns for high performance liquid chromatography, flow reactors and flow cells for detectors, devices for passive concentration of toxic compounds and various integrated devices that allow significant improvements in chemical analysis. A special attention is paid to the complexity and functionality of 3D-printed devices.

Abstract

One of the essential themes in modern catalysis is that of bridging the gap between its homogeneous and heterogeneous counterparts to combine their individual advantages and overcome shortcomings. One more incentive can now be added to the list, namely the ability of transition metal complexes to provide strong nuclear magnetic resonance (NMR) signal enhancement upon their use in homogeneous hydrogenations of unsaturated compounds with parahydrogen in solution. The addition of both H atoms of a parahydrogen molecule to the same substrate, a prerequisite for such effects, is implemented naturally with metal complexes that operate via the formation of a dihydride intermediate, but not with most heterogeneous catalysts. Despite that, it has been demonstrated in recent years that various types of heterogeneous catalysts are able to perform the required pairwise H2 addition at least to some extent. This has opened a major gateway for developing highly sensitive and informative tools for mechanistic studies of heterogeneous hydrogenations and other processes involving H2. Besides, production of catalyst-free fluids with NMR signals enhanced by 3-4 orders of magnitude is essential for modern applications of magnetic resonance imaging (MRI), including biomedical research and practice. The ongoing efforts to design heterogeneous catalysts which can implement the homogeneous (pairwise) hydrogenation mechanism are reported.

Abstract

Results of studies on the analytical capabilities of gold nanoparticles in the methods of optical molecular absorption spectroscopy are reported. Peculiar effects of the nature of nanoparticle stabilizer, its charge, morphology of nanoparticles, form in which they are present in the system (in a colloidal solution or as a part of a nanocomposite with polyurethane foam) upon the determination of organic compounds (thiols, cationic compounds, catecholamines) and inorganic anions are considered. The determination is based on aggregation of nanoparticles or change in the state of their surface and morphology as a result of silver coating, leading to significant spectral and color changes, which can be monitored both by optical molecular absorption spectroscopy and visually. The ways to increase sensitivity and to control selectivity of the analysis using gold nanoparticles and their nanocomposites are outlined.

Abstract

Colchicine derivative bearing substituted bispidine moiety, namely N-{7-(3,7-Di-(tert-butoxycarbonyl)-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonan-9-yl)-oxy-7-oxoheptanoyl}-N-deacetylcolchicine, was synthesized and tested for its effect on the net of microtubules (MT) in lung cancer cells A549. The compound induced not only MT depolymerization but stimulated the formation of small tubulin aggregates and long tubulin fibrils localized mainly around nuclei. The assemblies were morphologically different from tubulin clusters induced by structurally related anticancer agent tubuloclustin. The biotests data demonstrate that the depolymerization takes place for both pure tubulin and tubulin in cellulo, while fibrils are formed only in the cells. The research data of structure–activity relationship for several similar colchicine derivatives synthesized in the work give evidence for the proposition that the initial conjugate may interact not only with tubulin and MT in the cells, but also with MT-associated proteins, involved in the process of tubulin polymerization. The ability to affect simultaneously MAP – tubulin interactions opens attractive prospects in the design of novel anticancer agents.

Abstract

The article describes a comprehensive mass spectrometric approach to the study of surfaces of structural materials. The combined use of thermal desorption mass spectrometry, gas and liquid chromatography, and laser desorption/ionization mass spectrometry (LDI) to provide information about the surface and surface layers of materials is proposed. The suggested method allows one to determine the thermodynamic characteristics of compounds and surface contaminants adsorbed on surfaces, as well as surface layers, to determine the composition of volatile and non-volatile contaminants on the surface, and to determine the nature of the distribution over the surface of these compounds. The method allows to obtain the most complete information about the surface condition and can be used to predict the life of structural materials.

Abstract

By the methods of MALDI and mass spectroscopy with the detection of positively and negatively charged ions, it was found that the reaction of elemental sulfur and 1,3-dimethylimidazolium dimethylphosphate is accompanied by the opening of the S8 ring. 1H, 13C, 15N and 31P NMR spectroscopy showed that the interaction of S8 and 1,3-dimethylimidazolium dimethylphosphate proceeds exclusively on the oxygen atom of the dimethylphosphate anion carrying a negative charge. Kohn-Sham calculations at B3LYP/STO-3G, B3LYP/6-31G* and B3LYP/6-311G* levels of theory confirmed that the reaction of S8 with dimethylphosphate anion is possible.

Abstract

It is shown that self-heating of a compacted sample made of nonpassivated iron nanopowder is not uniform, although it begins simultaneously within the entire surface of the sample. It is found that the maximum temperature of self-heating decreases with an increase in relative density of samples, which indicates that the oxidation process is limited by the diffusion supply of oxidant. It is shown that the process of interaction of samples with the air occurs in a superficial mode. A qualitative agreement of the results of the theoretical analysis with experimental data is obtained. The possibility of passivation of compacted samples made of iron nanopowder is experimentally established.