Search

A series of polyhydroxyl sulfides and triazoles was prepared by reacting allyl and propargyl d-mannose derivatives with selected thiols and azides in thiol-ene and Huisgen click reactions. Conformational analysis by NMR spectroscopy proved that the intrinsic rigidity and linear conformation of the mannose derived polyol backbone is retained in the final click products in solution. Single crystal X-ray structure determination of one of the compounds prepared further verified that the linear conformation of the polyol segment is also retained in the solid state. In addition, an improved method for direct Barbier-type propargylation of unprotected d-mannose is reported. The new reaction protocol, involving tin-mediated propargylation in an acetonitrile-water mixture, provides access to multigram quantities of the desired, valuable alkyne polyol without relying on protecting group manipulations or chromatographic purification.

Environmental issues are always relevant. Nature is subject to constant human intervention. At the same time, associated institutions are being created to solve the tasks of reducing the level of harmful effects and the full restoration of environment. In this article, we assess the level of harmful emissions and wastes of oil and gas complex facilities during drilling, construction of facilities for field development and their operation, and present basic measures to reduce their impact on the air in Potochnoye field. We have examined the amount of emissions and waste from stationary and mobile sources. During wells drilling and facilities construction, the average annual evidence of pollutant emissions into the atmosphere caused by stationary sources will amount to 141.29 tons per year while the pollutant emissions caused by road and construction equipment and vehicles will be equal to 200.8 tons per year. Every year the amount of emissions into the atmosphere caused by the maintenance of the designed facilities will be 13730.9 tons per year, emissions from vehicles will be 47.1 tons per year. During field development, all work on the field should be carried out in compliance with the standards of the legislation of the Russian Federation. Having analyzed the amount of estimated emissions, a set of measures has been drawn up with the objective to reduce the impact of oil and gas complex on atmospheric air.

New lower-rim tetrasubstituted p-tert-butylthiacalix[4]arene derivatives bearing alkyl, propargyl, or triazole-containing substituents were synthesized. The structures of these compounds were determined by 1D and 2D NMR spectroscopy in solution and by X-ray diffraction in the solid phase. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) of azides to a mixture of 1,3-alternate–partial cone stereoisomers of dipropargyl derivatives of thiacalix[4]arene affords triazole-containing products exclusively in the 1,3-alternate conformation.

Novel electrochemical aptasensors based on glassy carbon electrodes modified with electropolymer- ized Neutral red and polycarboxylated macrocyclic li- gands onto which the DNA aptamers were covalently at- tached have been developed for detection of Aflatoxin B1 (AFB1). The interaction with an analyte resulted in the decrease of the cathodic peak current of the probe measured by CV and in the increase of the electron trans- fer resistance determined by EIS. The limit of detection was found to be 0.1 nM for CV and 0.05 nM for EIS methods, respectively. The aptasensor makes it possible to detect AFB1 in peanuts, cashew nuts, white wine and soy sauce with a recovery of 85-100 %.

A convenient procedure has been developed for the synthesis of p-tert-butylthiacalix[4]arene derivatives modified at the lower rim with anthraquinone fragments linked through acetamide spacers. The products showed moderate fluorescence in the region λ 520–620 nm.

The receptor properties of metastable polymorphic forms of 5,11,17,23-tetra(tert-butyl)-25,26,27,28-tetrakis[N-(2-ethoxycarbonyl(methyl)carbamoylmethoxy]-2,8,14,20-tetrathiacalix[4]arene in the cone and partial cone configurations obtained by the crystallization of their solutions in an organic solvent were studied. The ability of the studied calixarenes to “remember” the history of interaction with individual vaporous organic guests and their mixtures was discovered. The observed different effects of methanol and ethanol vapors on the phase state of the studied calixarene in the cone configuration can be used for qualitative and quantitative analyses of ethanol in binary mixtures. Calixarene in the partial cone configuration can remember the earlier bound methanol. The “memory” effect appears as a specific polymorphic transition in the receptor phase after bound methanol leaving on heating the clathrate. This effect is not observed for other studied guests.

An electrochemical aptasensor for ochratoxin A (OTA) detection has been developed on the base of a gold electrode covered with electropolymerized neutral red and silver nanoparticles obtained by chemical reduction with macrocyclic ligands bearing catechol fragments. Thiolated aptamers against OTA were covalently attached to silver nanoparticles via AgS bonding. The interaction with OTA induced the conformational switch of the aptamer, which caused increase of the charge transfer resistance measured by EIS in the presence of ferricyanide ions. The LOD achieved (0.05 nM) was comparable to other electrochemical aptasensors employing sophisticated assembling technique and enzyme amplification of the signal. The aptasensor was validated in spiked beer samples. The recovery of the OTA determination was found to be 66.3 14.1 % for light beer and 64.3 1.8 % for dark beer.

New acetylcholinesterase biosensors have been developed on the base of screen-printed electrodes modified with Co-phtalocyanine and polycarboxylated thiacalixarenes as enzyme support. The biosensors showed improved operational and analytical characteristics and high accuracy of the signal measurement. The biosensors developed made it possible to detect 3–200 ppb of paraoxon and 1–50 ppb of malaoxon with detection limits down to 2 and 0.05 ppb, respectively (incubation time: 15 min). The influence of macrocyclic receptors was related to nonenzymatic accumulation of the analytes within the surface layer and electrostatic interactions with remaining free carboxylic groups of the support. The reliability of the inhibition measurements was confirmed by testing spiked samples of sparkling and tape waters.

An amperometric aptasensor has been developed by immobilization of DNA aptamer with Neutral Red (NR) on polycarboxylated thiacalix[4]arene onto the electropolymerized NR layer at a glassy carbon electrode. The NR reduction current recorded after 10 min incubation decayed with increased thrombin concentration due to limitation of the electron exchange in the surface layer. The aptasensor makes it possible to determine 0.1–50 nM of thrombin (limit of detection 0.05 nM). The aptasensor can be used for the direct determination of thrombin in blood serum and does not exert any alteration of the response in the presence of 100 fold excess of serum proteins.

A sensitive electrochemical sensor based on a composite containing silver nanoparticles and a redox active thiacalixarene with catechol fragments in the substituents at the lower rim has been developed and used for dopamine detection. The electrochemical investigation of thiacalixarene in homogeneous solution and on the electrode interface showed the reversible character of the redox conversion of catechol fragments and its involvement in the chemical reduction of silver which resulted in formation of uniform nanoparticles of 4–6 nm in diameter. The use of such a material for electrode modification made it possible to record a high amplitude cathodic signal at −700 mV that was proportional to the dopamine concentration within 1 nM–1 µM. (limit of detection 0.5 nM).

The performance of potentiometric sensors based on carbon screen-printed and glassy carbon electrodes covered with polyaniline (PANI) and thiacalix[4]arene receptors have been compared in the determination of some ions and discrimination of green tea brands. The optimization of PANI electropolymerization provided satisfactory characteristics of screen-printed electrodes comparable with those of conventional sensors based on glassy carbon. The potentiometric sensors make it possible to determine 1×10−2–1×10−6 M Fe3+ ions. Also, successful discrimination of twelve tea brands was performed with three-sensor array. The 100 % true prediction was confirmed by principal component analysis (PCA) and linear discriminant analysis (LDA).

A series of new p - tert -butyl thiacalix[4]arenes with o -, m -, p -amido and o -, m -, p -(amidomethyl)pyridine substituents at the lower rim in cone , partial cone , and 1,3- alternate conformations were synthesized. The ability of the obtained compounds to recognize the α-hydroxy (glycolic, tartaric) and dicarboxylic (oxalic, malonic, succinic, fumaric, and maleic) acids was investigated by UV–vis spectroscopy. Also, the efficiency and selectivity of binding, the association constants log K a (10 2 to 10 7 M −1 ) and the stoichiometry were determined for the complexes of p - tert -butyl thiacalix[4]arenes with the acids. The receptors based on p - tert -butyl thiacalix[4]arenes with (amidomethyl)pyridine substitutes are most efficient in complexation in many cases.

Two approaches to controlled synthesis of the organo-inorganic materials obtained by one- and two-stage surface modification of nanosized silica particles by p-tert-butyl thiacalix[4]arene derivatives have been developed and compared. The possibility of the synthesis of the mono- or low-disperse hybrid organo-inorganic particles with hydrodynamic diameter varying in the range of 23.92–137.1 nm depending on stereoisomer and reaction mixture dilution was shown via surface modification of the silica particles. The direct acylation of aminated silica leads to covalent macrocycle-silica hybrid clusters of micron size. The grafting reaction was confirmed by IR-, UV-spectroscopies, dynamic light scattering and thermal analysis.

New aptasensors based on DNA aptamer and polycarboxylated thiacalix[4]arenes in cone, 1,3-alternate and partial cone configurations bearing Neutral Red (NR) at substituents at the lower rim have been developed and applied for thrombin detection. The assembly of the biorecognition layer was optimized by AFM and EIS study to reach the maximal coverage and regular composition of the surface layer. The interaction of the NR groups with thrombin suppressed the electron hopping between oxidized and reduced mediator groups. This regularly decreased the NR peak current and increased the resistance of the charge transfer. The aptasensor makes it possible to detect from 1 nM to 1 μM of thrombin with the detection limit of 0.05–0.5 nM. No effect of the 1000 excess of bovine serum albumin on the signal was observed. The influence of thiacalix[4]arene configuration on the sensitivity of aptasensor signal toward thrombin is discussed.