Evaluation of Free Radical-Scavenging Activity of Sea Urchin Pigments Using HPTLC with Post-Chromatographic Derivatization

Chromatographic separation, analysis of in situ radical-scavenging activity, and quantitative analysis of green sea urchin shell pigments were carried out by online HPTLC-DAD and HPTLC-DPPH methods. Methanol:chloroform:acetic acid:water (11:50:5:2, v/v) was selected as the best mobile phase on silica gel plates for the separation of the pigments. Two pigment spots, S1 and S2, were observed on the TLC plates, while echinochrome A was not detected in the pigment extract of green sea urchin shells. Based on the estimated ID₅₀ values, the antiradical activity was S2 (0.043 μg) > S1 (0.058 μg) > echinochrome A (0.134 μg).     

A Convenient Approach to 4,7‐Dihydrotetrazolo [5,1‐c][1,2,4]triazine Synthesis

Azo coupling of 1,3‐dicarbonyl compounds with tetrazolyl‐5‐diazonium chloride is used to develop a convenient one‐step procedure for the synthesis of 4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines. In contrast to nonfluorinated analogs, 7‐hydroxy‐7‐polyfluoroalkyl‐4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines undergo a ring‐chain isomerism resulting from the cleavage at the C7―N7a bond. A distinctive feature of nonfluorinated 4,7‐dihydrotetrazolo[5,1‐c][1,2,4]triazines is the possibility to dehydration, which is accompanied by an azide rearrangement due to the tetrazole ring cleavage with the formation of tetrazolo[1,5‐b][1,2,4]triazines.     

XPS study of the electronic structure of heterometallic complexes Fe2MO(Piv)6(HPiv)3 (M = Ni, Co)

Heterometallic complexes Fe₂MO(Piv)₆(HPiv)₃ (M = Ni, Co) have been studied by XPS. The complexes are identified as high-spin complexes with metal atoms in oxidation states M(II) and M(III). A change in the ligand environment of metal atoms has an effect on both the energetic state of metal atoms and the XPS pattern. The substitution of a Co atom for the nickel atom in the heterometallic complexes changes the XPS pattern of iron and their magnetic state. For the Fe₂MO(Piv)₆(HPiv)₃ complexes, quantum-chemical calculations have been performed at the density functional theory (DFT) level. In combination with XPS and magnetochemistry data, the quantum-chemical calculation demonstrates that the Fe, Ni, and Co atoms in the trinuclear complexes are in the high-spin local state and that the ground state is dominated by antiferromagnetic exchange interaction.     

Preparation of aqueous sols of Ce1 − x Gd x O2-δ, Y0.9Eu0.1VO4 and nanocomposites Ce1 − x Gd x O2-δ/Y0.9Eu0.1VO4 stabilized by polyacrylic acid

A method for the synthesis of stable aqueous sols of nanocrystalline solid solutions Ce_1?x Gd _x O_2-δ (x = 0.10, 0.15, 0.20) and Y_0.9Eu_0.1VO₄ and nanocomposites Ce_{1 ? x} Gd _x O_2-δ/Y_0.9Eu_0.1VO₄ stabilized by biocompatible low-molecular-weight polyacrylic acid was proposed. Polyacrylic acid was shown to be a promising matrix for the preparation of polyfunctional composite materials.     

Reactions of 2- and 4-pyrones with secondary phosphine chalcogenides: a facile synthesis of functional phosphorylated pyrones

The oxidative cross-coupling between 4-hydroxy-6-methyl-2-pyrone or 3-hydroxy-2-methyl-4-pyrone and secondary phosphine chalcogenides proceeds in CCl₄/Et₃N under mild conditions (20–52 °С, 0.75–10 h) through the hydroxyl group to give O-(6-methyl-2-oxo-2H-pyran-4-yl) diorganylphosphinochalcogenoates or O-(2-methyl-4-oxo-4H-pyran-3-yl) diorganylphosphinochalcogenoates, in high yields.     

Wetting behavior of pulmonary surfactant aqueous solutions

The wetting properties of pulmonary surfactant aqueous solutions with respect to solid surfaces with different degree of hydrophobicity have been studied. The contact angles θ of drops from a pulmonary surfactant solution onto SiO₂-glass surfaces have been measured as a function of their degree of hydrophobicity θ _w. The completely hydrophilic SiO₂-glass surface is essentially hydrophobized by the animal-derived pulmonary surfactant Curosurf. The hydrophobization depends on the surfactant concentration—the contact angles increase with increasing the Curosurf concentration C _s in the low concentration range, but they remain almost constant in a wide range of C _s >90 μg/ml. Additions like NaCl and bovine serum albumin influence the θ-values. The contact angles θ naturally increase with increasing θ _w but this dependence is not linear—the curve steepens at larger θ _w values. The thickness h of the wetting thin liquid films from Curosurf aqueous solutions depends on the hydrophobicity θ _w of the solid surface and the h(θ _w) curves always pass a minimum. The h-values, as well as the h(θ _w) curve, are mainly determined by the steric and hydrophobic disjoining pressures, which depend on the orientations and conformations of the molecules adsorbed on the solid surface from the very complicated multi-component aqueous solutions.     

Physical properties and inclusion interactions of new stilbazolium salts: experimental versus theoretical study

The experimental and theoretical spectroscopic and spectrometric elucidation in solid-state and gas-phase on the interacting ionic species of applied oriented synthetic derivatives on the base of the stilbazolium salts as molecular template was reported. The correlation between the molecular structure, and vibrational properties within THz-regime (10-0.3 THz) was performed. The collective vibrations, and gas-phase stabilized ionic species were comprehensive studied by the Raman spectroscopy and matrix-assisted laser desorption/ionization mass spectrometry, using the embedded organic dyes in host matrixes. The performed solid-state quantum chemical calculations contributed to further understanding of the nature of the guest–host interacting systems as well as to explain the observed optical phenomena within the THz-region.     

Heptachlorepoxides: theoretical versus experimental study of the embedded samples in the matrixes of organic crystals

The analysis of heptachlorepoxides in gas- and condense phase of embedded in the organic matrixes analyte samples is highlighted. The electrospray ionization, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS), nuclear magnetic resonance, Raman and CD spectroscopy as well as quantum chemical methods are used. The competitive formation of the variety of epoxides, strongly depending of the reaction conditions. Thus, the products of interaction of matrix-analyte matrixes under the UV–MALDI–MS experiment are comprehensively examinated. Nonetheless, that for heptachlor (HA) is known an epoxide, existing in two isomeric forms, i.e. A and B (exo- and endo-one), the study on the mechanism of the epoxidation of HA, showed formation of new epoxides C–F and an intermediate (I), characterizing with high stability, decreasing in the raw F > A > C > B > I > D > E. The epoxide D appeared enantiomer of the insecticide oxychlodran. The reported results on the pesticides, their metabolites and decomposition reactivity products contributed significantly to the field of analytical chemistry, providing possibility for elaboration of highly selective protocols for assessment of environmental contaminant issues.     

Kinetics of Absorption of Carbon Dioxide and Sulfur Dioxide in Fluorine-Containing Media

Kinetics and Catalysis - It has been established that the reactions of sulfur dioxide oxidation and carbon dioxide conversion take place in aqueous suspensions of calcium fluoride at room...     

Metal-Carbon Composites Based on Carbonized Melamine-Formaldehyde Polymer and Their Electrocatalytic Properties

Russian Journal of Electrochemistry - Metal/N-doped carbon (M/C–N) composites were prepared using the melamine-formaldehyde polymer (MFP) as a source of C–N carbon and a metal salt...