Mixed phosphonium-iodonium ylides are of interest as reactants for the synthesis of new heterocyclic compounds. Recently it has been shown that under irradiation the reactions of phosphonium-iodonium ylides occur with the formation of radicals. The radicals generated in the photolysis of the ylide itself and its fragments, diphenyliodonium salt and triphenylphosphine, or compounds participating in its reactions, dichloromethane and phenylacetylene, are studied with the use of PBN and DMPO spin traps. The obtained results confirm the radical mechanism of the ylide photodecomposition and have allowed us to specify the composition of the primary radicals generated in the photolysis. The unknown EPR parameters of spin adducts are determined for some radicals.

Hybrid nanosystems based on iron oxide nanoparticles (IONPs) and human serum albumin (HSA) were synthesized. The size and composition of HSA@IONP nanosystems were characterized using UV/visible spectrophotometry (particularly, using the Bradford protein assay), dynamic light scattering (DLS), and electron magnetic resonance. The dark and photoinduced cytotoxicity of these systems were studied using methylene blue (MB) as a model photosensitizer (PS). The analysis of the survival of cultured tumor cells of the human breast adenocarcinoma line MCF-7 showed an increase in photoinduced cytotoxicity upon excitation of the PS accumulated by cells due to delivery via the nanosystems, compared to the free PS in equivalent concentrations. HSA@IONPs are discussed as a promising platform for the targeted delivery of a PS to tumor cells.

Combined effects of electrolysis and ultrasound on the population of E. coli bacteria in aqueous solution of sodium sulfate were investigated. The kinetics of bacteria inactivation was determined employing these water purification techniques. It has been shown that the combination of ultrasonic and electrochemical treatments of aqueous solution significantly increases the rate of bacterial inactivation. It has been suggested that hydroxyl radicals formed as a result of the reaction occurred after treatment of aqueous solution by employing a combination of electrolysis and ultrasound are responsible for the death of bacteria. A correlation between the rate of hydroxyl radical formation and the inactivation rate of bacteria has been obtained.

In this paper, we provide a thorough electrochemical study of redox-active nanosized cationic gels which are promising materials for redox flow battery electrolytes. We use two-step synthesis under mild aqueous conditions: precipitation polymerization of nanogels based on poly-(N-isporopylacrylamide-co-N-(3-aminopropyl) methacrylamide hydrochloride) (PNIPAM-co-APMA), and grafting of redox-active 4-(3-carboxypropanamido)TEMPO units to the nanogels. We demonstrate stable reduction-oxidation behavior of such nanogels and suggest a universal approach to evaluate the "effective" concentration and diffusion coefficient of redox-active groups grafted to nanogel particles. For the TEMPO-grafted PNIPAM-co-APMA nanogels we find the "effective" concentration of TEMPO-groups to be approximately 50 % of their total concentration and demonstrate an increase of the "effective" concentration upon electrode rotation. Also, we investigate electron transfer kinetics of redoxactive nanogels and provide an evidence that the adsorbed layer of nanogels facilitates electron transfer.

The reactions of acetylcholine halides with H2O2 were studied at room temperature in initially deionized water, i.e., at pH ∼7. Acetylcholine (ACh), which catalyzes the decomposition of hydroperoxides and H2O2 into radicals in an organic medium, virtually does not affect the decomposition of H2O2 in aqueous solutions. In the case of AChI, hydrogen peroxide oxidizes the iodide anion to form diiodine and hydroxyl radical HO•, which was identified using the 5,5-dimethylpyrrolidine N-oxide spin trap. The rate constant of this reaction was estimated from the initial sections of the kinetic curves for the consumption of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL): k1 = (2.0±0.1)•10−3 L mol−1 s−1. A nontrivial combination of radical reactions and redox disproportionation reactions occurs in the AChI—H2O2—TEMPOL system in initially deionized water. In this medium, H2O2, iodine compounds, TEMPOL, and the formed hydroperoxide radicals HO2• have a dual ability to act as oxidants or reducing agents, which results in quasi-stationary concentrations of I2 and TEMPOL being established in the process. The I− oxidation by peroxides in acid medium, known in iodometric titration, generates hydroxide radicals when conducted in neutral solutions (pH ∼7) and can compete with the Fenton reaction in systems in which the presence of metal ions is excluded.

For the first time cobalt-manganese spinel structure catalysts were effectively applied for aerobic oxidation of sulfur-containing compounds. High activity of obtained catalysts is achieved due to the existence of the redox couples Co2+/Co3+ and Mn3+/Mn4+ in the spinel structure. It has been shown that the high mobility of oxygen in the spinel structure contributes to the efficient oxidation of sulfur-containing compounds. The CoMn2O4 and MnCo2O4 spinel-type catalysts were obtained by the hydrothermal method and characterized by a complex of physicochemical methods: XRD, FTIR, nitrogen adsorption-desorption, SEM, TEM, TPR-H2, and XPS. Under optimal conditions (130 degrees C, & omega;(cat.) = 0.034 wt%, 2 h), the complete DBT oxidation was achieved in the presence of CoMn2O4. High stability of catalyst over 5 cycles of oxidation was demonstrated. A possible reaction mechanism has been proposed based on EPR data and catalysts characterization results.

It is shown that one-electron oxidation of aniline with methylene blue is possible only at low temperatures under UV radiation. The kinetics of aniline polymerization under the action of ammonium persulfate in the presence of catalytic amounts of methylene blue is studied. Kinetic curves are obtained by electron paramagnetic resonance (EPR) spectroscopy at various temperatures and concentrations of methylene blue. The catalytic action of the unassociated form of methylene blue and the deactivation of reactive complexes by the dye dimers are shown to compete. In the context of the obtained results the autocatalysis mechanism of oxidative polymerization is considered, which suggests the formation of complexes of aniline and polyaniline that are subject to subsequent rapid oxidation by the persulfate anion. The unassociated form of methylene blue (MB), which simulates the Q of the emeraldine salt catalyzes the polymerization of M through the formation of charge transfer complexes. The dimeric form of MB deactivates QM. Polyaniline is not a direct oxidizer for M and the autocatalysis mechanism includes the formation and subsequent oxidation of QM with the release of active centers M+.. image

The reactivity of ylides possessing additional iodonium functionality is driven by the departure of the iodonium group, which generates highly reactive intermediates. The scope of these reactions depends on both the nature of the reacting partner and the functional groups present at the ylidic center. In this study, we investigate the reactivity of phosphonium-iodonium ylides, where the ylidic carbon atom is bonded to a cyclic phenoxaphosphonium moiety and various electron-withdrawing substituents. The study examines these ylides in reactions with nitriles and alkynes, continuing our investigation of acyclic phosphonium-iodonium ylides with triple-bond-containing compounds. The incorporation of phosphorus into a cyclic structure reveals new bond-making and bond-breaking patterns in reactions with alkynes, leading to novel reaction pathway and the formation of enone-functionalized phosphonates. Phenoxaphosphonium-iodonium ylides and furans have been shown to have antiproliferative activity in vitro against several human cancer cell lines.

Annulation of mixed phosponium-iodonium ylides and compounds with a triple bond is an interesting example of the synthesis of different types of heterocycles in one-pot, metal-free systems at ambient temperature to give substituted oxazoles in the reaction with nitriles and phosphorus-containing lambda(5)-phosphinolines and substituted furans in the reaction with acetylenes. The iodonium group in the mixed ylides provides the possibility for the radical initiation of the reaction. Herein, we investigated the generation of primary radicals and the formation of phosphorus-containing products in the photolysis of benzoyl phosphonium-iodonium ylide alone and in its reaction with acetylenes in DCM by EPR and P-31 NMR spectroscopies with the use of two most popular spin traps, PBN and DMPO. The results allowed us to account the crucial difference in the registered radicals in the two systems for the aggregation of the components, with ylide molecules forming a core and acetylene molecules being a shell of the aggregates in DCM, in which the annulation occurs. The peculiarities of the reactions of PBN and DMPO with generated radicals are discussed.

The combined effects of electrolysis and ultrasound on the population of E. coli bacteria in an aqueous solution of sodium sulfate have been studied. The kinetics of bacterial inactivation with this method for water purification have been determined. It has been shown that the combined effect of ultrasonic and electrochemical treatment of an aqueous solution significantly increased the rate of bacterial inactivation. It has been suggested that hydroxyl radicals formed during combined treatment are responsible for the death of bacteria. A correlation has been found between the rate of formation of hydroxyl radicals and the rate of inactivation of bacteria.

Mixed phosphonium-iodonium ylides effectively undergo the photochemical reaction of heterocyclization. For most mixed phosphonium-iodonium ylides, the main stage of photolysis was the homolytic cleavage of the C—I bond of the ylide molecule with the formation of radicals. ESR spectroscopy was used to study radicals formed during the photolysis of the mixed benzoyl-substituted phosphonium-iodonium ylide in acetonitrile and alcohols. The hyperfine coupling constants of the registered radicals were determined and their structures were proposed.

βL-crystallin aggregation due to oxidative damage in the presence of H2O2 and ferric chloride was studied in-vitro under conditions close to physiological. It was shown that the protein aggregation characterized by the nucleation time and the aggregation rate significantly depended on the composition of the isoosmotic buffers used, and decreased in the series HEPES buffer > Tris buffer > PBS. Ferric chloride at neutral pH was converted into water-insoluble iron hydroxide III (≡FeIIIOH). According to the data of scanning electron microscopy the ≡FeIIIOH particles formed in HEPES buffer, Tris buffer, and PBS practically did not differ in structure. However, the sizes of ≡FeIIIOH floating particles measured by dynamic light scattering differed significantly and were 44 ± 28 nm, 93 ± 66 nm, 433 ± 316 nm (Zaver ± SD) for HEPES buffer, Tris buffer, and PBS, respectively. It was found by the spin trap method that the ability of ≡FeIIIOH to decompose H2O2 with the formation of a •OH decreases in the series HEPES buffer, Tris buffer, and PBS. The authors suggest that the ability to generate •OH during the decomposition of H2O2 is determined by the total surface area of ≡FeIIIOH particles, which significantly depends on the composition of the buffer in which these particles are formed.

Food products change their quality during storage not only under the external impact, but also because they are complex in composition. As a result, food scientists look for new methods to control these internal changes. The research objective was to describe the changes in the physicochemical properties of apple puree during storage at elevated temperatures (40–60°C) and link them with the changes in the sensory profile. The study featured homogenized apple puree packaged in composite material and heated up to 40, 50, and 60°C. The colorimetric studies were conducted at 45°/0°, light source D65. The proton relaxation time and the water diffusion coefficient (impulse gradient method) were studied at a frequency of 20 MHz. The analysis of molecular dynamics involved the method of electron paramagnetic resonance of spin probes. The samples were cooled down to –70°C to measure the content of non-crystallizing water by the method of differential scanning calorimetry. The color change rate was constant and followed the zero-order kinetic reaction equation with an activation energy of 92 kJ/mol. The changes in color, proton relaxation, and sensory properties correlated when the samples were stored at 50 and 60°C. The analysis of the magnetic relaxation time, the diffusion coefficient of water, and the content of non-crystallizing water indicated that the main changes in the physical structure of the puree during heat treatment occurred as a result of the aggregation of apple cell fragments. These findings were confirmed by the optical microscopy. A prolonged exposure to 40–60°C affected the color, the relaxation of water protons, and the size of aggregates of apple cell fragments. It also affected the amount of water that did not crystallize at –70°C. The correspondence between the values of the activation energies was determined by the methods of colorimetry and proton relaxation. Therefore, the coloration and the water changes depended on the same processes. These physical and chemical properties can be used for quantitative assessment of apple puree under thermal treatment.

The process of complex formation between polyethylenimine and copper cations in an aqueous solution, followed by isolation of copper nanoparticles, has been studied by means of ESR spectroscopy. It has been shown that in excess of the polymer in the solution the copper cation forms complex containing three nitrogen atoms in the coordination sphere, with distorted tetragonal geometry. The increase in copper concentration has led to the formation of the copper cation complex with water. Addition of the reducing agent NaBH 4 to the studied solutions has led to the formation of copper nanoparticles accompanied by gradual disappearance of the ESR signal of Cu(II) and the appearance of the ESR signal typical of the mononuclear copper complexes with polyethylenimine.

The phenomenon of selective sorption of a stable nitroxyl radical TEMPO on rubber particles in the powder of dried and dispersed root of kok-saghyz has been discovered. This feature of the rubber-bearing root material has contributed to the development of a new, highly sensitive method of quantitative analysis of rubber by measuring the integrated intensity of the EPR TEMPO signal. The main advantages of the proposed method are the speed and the ability to determine the content of rubber directly in the roots of the plant in microquantities (5–30 mg).

The generation of hydroxyl radicals from hydrogen peroxide in aqueous solutions containing magnetic nanoparticles (MNPs), hemoglobin (Hb), immunoglobulin G (IgG), and human serum albumin (HSA) was determined. The dependence of the rate of formation of the oxidized product of o-phenylenediamine (o-PDA) on the concentration of MNPs in solution, as well as on the concentration of proteins, was obtained. The peroxidase-like activity of MNPs was shown to decrease in the presence of HSA and IgG, while the addition of Hb to the reaction mixture led to its decrease and increase depending on protein concentration. The obtained effects can be used in the engineering of systems based on MNPs for theranostics (in particular, for suppression of tumor growth) and in predicting the ability of particles to catalyze the generation of reactive oxygen species (ROS) in vivo.

By radical telomerization of N -vinyl-2-pyrrolidone in the presence of 2-aminoethanethiol an oligomer containing amino end groups and capable of stabilizing gossypol aqueous dispersions was synthesized. The telomerization kinetics of N -vinyl-2-pyrrolidone in the presence of 2-aminoethanethiol was studied by the dilatometric method, and the structure of the oligomer was characterized by 13 C NMR spectroscopy.

The paper presents a method to carry out a quantitative analysis of the content of natural rubber of Taraxacum kok-saghyz E. Rodin by measuring adsorption of the nitroxide radical TEMPO in root preparations of the said plant. The method is based on a comparison between the integrated intensity of an EPR signal of interest and a standard. The developed method of analysis makes it possible to quickly and with good accuracy determine the content of rubber of plant tissues without its extraction from rubber-containing biomass.

This paper deals with the development of polymeric nanocarriers based on amphiphilic copolymers of N-vinyl-2-pyrrolidone and acrylic acid of various molecular weights synthesized through the AIBN-initiated radical copolymerization of N-vinyl-2-pyrrolidone and acrylic acid in the presence of n-octadecyl mercaptan. The structure of the copolymers is characterized by H-1 NMR, C-13 NMR, IR and MALDI-TOF MS spectroscopy. It is shown that the length of the hydrophilic block defines the size of the nanoaggregates while impacting the steric stabilization efficiency and the probability of the interchain hydrogen bond formation. The hydrogen bonds formation between the residues of N-vinyl-2-pyrrolidone and acrylic acid is in agreement with the reduction of the zeta-potential of the nanoaggregates and the critical aggregation concentrations upon increasing the molecular weight. The presence of acrylic acid residues in the amphiphilic macromolecules leads to a higher affinity for doxorubicin and slow partial release of doxorubicin bonded with the aggregates' corona, which is helpful for reducing its cardiac toxicity. Nanoaggregates with a paclitaxel-loaded hydrophobic core are obtained, showing the possibility of dual loading. The amphiphilic copolymers of N-vinyl-2-pyrrolidone and acrylic acid containing an n-octadecyl thio end group are thus promising candidates for combination cancer therapy with immobilized anti-cancer drugs, paclitaxel, and doxorubicin.

Magnetic nanosystems (MNSs) consisting of magnetic iron oxide nanoparticles (IONPs) coated by human serum albumin (HSA), commonly used as a component of hybrid nanosystems for theranostics, were engineered and characterized. The HSA coating was obtained by means of adsorption and free radical modification of the protein molecules on the surface of IONPs exhibiting peroxidase-like activity. The generation of hydroxyl radicals in the reaction of IONPs with hydrogen peroxide was proven by the spin trap technique. The methods of dynamic light scattering (DLS) and electron magnetic resonance (EMR) were applied to confirm the stability of the coatings formed on the surface of the IONPs. The synthesized MNSs (d ~35 nm by DLS) were intraarterially administered in tumors implanted to rats in the dose range from 20 to 60 μg per animal and studied in vivo as a contrasting agent for computed tomography. The long-term (within 14 days of the experiment) presence of the MNSs in the tumor vascular bed was detected without immediate or delayed adverse reactions and significant systemic toxic effects during the observation period. The peroxidase-like activity of MNSs was proven by the colorimetric test with o-phenylenediamine (OPD) as a substrate. The potential of the synthesized MNSs to be used for theranostics, particularly, in oncology, was discussed.