A. A. Revina

The mechanism of interaction of carnosine with superoxide radicals in water solutions

The antiradical activity and the radiation stability of carnosine in water solutions was studied by the pulse radiolysis technique with spectrophotometric registration of absorbance. The transient spectra were recorded in the range 245-670 nm during 2 x 10(-6)-20 s after the pulse using a flow system for continuous change and saturation of the samples by different gases. Also, the spectra of the stable products of radiolysis were studied. The results obtained give evidence that carnosine in water solutions in the presence of oxygen behaves like a multifunctional antioxidant. Even at low concentrations, dipeptide forms a charge-transfer complex (Car ... O2-., lambda max = 265 nm) with the superoxide radical which changes the reactivity of O2-.. The absorbance band of the complex was shifted towards lower energy as compared to superoxide radical lambda max = 255 nm). The interaction of carnosine with OH-radicals proceeding at very high rate and resulting in the formation of a stable product suggested another type of dipeptide activity. The kinetic mechanism of the interaction of carnosine with products of radiolysis of water in aerobic conditions is discussed.

Adsorption of Copper and Calcium Cations on Polarized Activated Carbon Modified by Quercetin

The effect of immobilized quercetin on activated carbon on Cu 2 + and Ca 2 + adsorption, as a function of a potential, was investigated. Ranges of potentials, corresponding to areas of selective adsorption of investigatedcations, were obtained. Ca 2 + ions do not adsorb on unmodified activated carbon AG-3V. In contrast, the modification of the activated carbon increases the adsorption activity of Ca 2 + . There are two areas of selective adsorption of Ca 2 + ions. The selective adsorption of Cu 2 + ions on unmodified sorbent was not found. The selective adsorption of Cu 2 + ions on the quercetin-modified activated carbon initiates at potentials near E = -0.25 V. Dissolved oxygen and the acidification of a solution, containing calcium or copper ions, decrease the adsorption activity on modified and unmodified activated carbons.

Retention Indices as the Most Reproducible Retention Parameters in Reversed Phase HPLC. Calculation for Hydrophilic Phenolic Compounds Using Reference n‐Alkyl Phenyl Ketones

Abstract A comparison of various presentation forms of retention parameters measured in multi‐step gradient elution regimes in reversed phase HPLC indicates that retention indices in the scale of n‐alkyl phenyl ketones (so‐called Smith′s RI system) have the maximal reproducibility. However, the determination of these parameters for most hydrophilic compounds eluted before the first reference acetophenone (RI=800) implies their calculation by extrapolation, that can lead to the high irreproducibility of results, especially in regimes with initial isocratic stages followed by fast gradient elution. This fact explains the necessity of elaboration of a new calculation method based on the extrapolation of retention concentrations, which provides the appropriate interlaboratory coincidence of RI values at least within the range 600–800 i.u. Using this algorithm, retention indices for about 60 phenolic compounds have been determined, that permits us to identify them in complex mixtures of natural plants extractive substances using HPLC without corresponding reference samples.

Interaction of carnosine with superoxide radicals in aqueous solutions

Carnosine was discovered to be able to interact with superoxide-anion and active hydroxyl radicals, using carnosine aqueous solutions. This interaction is specific and can be detected at carnosine concentrations more than 0.02 mM. Interaction of carnosine with O2 results in occurring of charge translocation complex with absorbtion maximum at 265 nm. Stability of this complex is dependent on the medium pH, decreasing with its acidification.

Catalytic activity of polymer-palladium metal nanocomposites in oxygen reduction and hydrogen oxidation reactions

Palladium/Nafion nanocomposites were synthesized by the radiation chemical reduction of palladium ions in reverse micellar solutions. The functional characteristics of the nanocomposites were studied by cyclic voltammetry, spectrophotometry, and scanning electron microscopy. The prepared nanocatalysts revealed a high activity in oxygen reduction and hydrogen oxidation reactions. The catalytic activity of the polymer-metal nanocomposites was shown to depend on the degree of solubilization and palladium nanoparticle size.

Physicochemical properties of surfaces of various nanomaterials according to gas-chromatography data

The thermodynamic characteristics of adsorption on original and modified silica and ultradispersed diamond adsorbents are determined using gas chromatography. The contributions of the dispersion and specific donor-acceptor interactions to the total adsorption energy are estimated and the relation between the properties of the modified specimens and the surface treatment is found. Based on the data obtained, donor and acceptor characteristics of the adsorbent surfaces studied are estimated.

The mechanism of interaction of ceruloplasmin with superoxide radicals.

1. The mechanism of interaction of CP with O2- radicals in chemical and enzymatic systems of superoxide radical generation as well as in the pulse radiolysis technique was studied. 2. It is found that CP does not exert any kinetic influence on the decomposition of superoxide radical and, unlike SOD, cannot catalyze the reaction of disproportionation of these radicals in systems with chemical and enzymatic generation of O2-. 3. The data obtained confirm the suggestion that CP interacts with precursors of O2- radicals. 4. The irradiation of CP does not change its inhibiting activity in the reaction of the formation of superoxide radicals in systems with enzymatic O2- generation, but decreases its oxidase activity. 5. The results obtained demonstrated that the increase in the radiation dose resulted in the decrease of the inhibiting activity of SOD, whereas the activity of CP did not change.

Study of nanoparticles synthesized in reverse micelles using liquid chromatography method

Liquid chromatography, which makes it possible to investigate interphase processes, is an additional method for studying inverse micellar systems without changing their properties in the process of sample preparation. In the case of using these systems to synthesize nanoparticles (NPs), it becomes possible to determine their adsorption characteristics, to investigate the processes of modifying surface adsorbents by NPs, to determine their sizes, and to divide them into fractions according to their sizes and surface properties of the micelles. The method is simple and rapid and permits one to use standard, relatively inexpensive equipment and can be applied in many physicochemical studies of NPs synthesized in micellar solutions.

Radiation-chemical transformations of coumarins in organic solvents

A spectrophotometric investigation into the radiation-chemical transformations of coumarins with different structures was performed. It was shown that the introduction of hydroxy, nitroso, and methyl groups into the coumarin molecule has a substantial effect on its radiation-chemical transformations. The solvated electron was supposed to be a reactive species responsible, for the most part, for coumarin degradation.

Catalytic Properties of Gold Nanoparticles Prepared in Reverse Micelles

Adsorption and catalytic properties of gold nanoparticles of various sizes prepared by two methods of reduction in reverse micellar solutions were studied. Gold nanoparticles are capable of adsorbing molecular hydrogen and exhibiting catalytic activity in reactions of ortho—para conversion of protium and deuterium—hydrogen exchange. The size dependence of the catalytic activity of gold nanoparticles in reaction of H2—D2 exchange regardless of the method of preparation was determined.