Crystallization and second harmonic generation in thermally poled niobium borophosphate glasses

Crystallization of glasses with compositions (1−x)(0.95 NaPO₃+0.05 Na₂B₄O₇)+xNb₂O₅, x=0.4, 0.43, 0.45, 0.48 was investigated by differential scanning calorimetry and X-ray powder diffraction. Crystallization of two phases was observed in the glasses with x=0.43-0.48. First phase is a sodium niobate with the structure of tetragonal tungsten bronze () and second phase is Na₄Nb₈P₄O₃₂ (). The crystallization of sodium niobate is correlated with increasing of nonlinear optical efficiency reported for thermally poled glasses with x>0.4. The results of Raman spectroscopy show the formation of three-dimensional (3D) niobium oxide framework in the glasses with increase of niobium concentration. This framework is supposed to have tetragonal tungsten bronze structure and to be responsible for nonlinear optical properties of the glass. Second harmonic generation signals of as prepared and crystallized glass after thermal poling are compared. The nucleation and crystallization do not improve the NLO properties of the glasses under study.     

Identification of extracellular nanoparticle subsets by nuclear magnetic resonance

Exosomes are a subset of secreted lipid envelope-encapsulated extracellular vesicles (EVs) of 50–150 nm diameter that can transfer cargo from donor to acceptor cells. In the current purification protocols of exosomes, many smaller and larger nanoparticles such as lipoproteins, exomers and microvesicles are typically co-isolated as well. Particle size distribution is one important characteristics of EV samples, as it reflects the cellular origin of EVs and the purity of the isolation. However, most of the physicochemical analytical methods today cannot illustrate the smallest exosomes and other small particles like the exomers. Here, we demonstrate that diffusion ordered spectroscopy (DOSY) nuclear magnetic resonance (NMR) method enables the determination of a very broad distribution of extracellular nanoparticles, ranging from 1 to 500 nm. The range covers sizes of all particles included in EV samples after isolation. The method is non-invasive, as it does not require any labelling or other chemical modification. We investigated EVs secreted from milk as well as embryonic kidney and renal carcinoma cells. Western blot analysis and immuno-electron microscopy confirmed expression of exosomal markers such as ALIX, TSG101, CD81, CD9, and CD63 in the EV samples. In addition to the larger particles observed by nanoparticle tracking analysis (NTA) in the range of 70–500 nm, the DOSY distributions include a significant number of smaller particles in the range of 10–70 nm, which are visible also in transmission electron microscopy images but invisible in NTA. Furthermore, we demonstrate that hyperpolarized chemical exchange saturation transfer (Hyper-CEST) with ¹²⁹Xe NMR indicates also the existence of smaller and larger nanoparticles in the EV samples, providing also additional support for DOSY results. The method implies also that the Xe exchange is significantly faster in the EV pool than in the lipoprotein/exomer pool.

Diffusion and xenon NMR based methods to determine a very broad range of sizes and sub-sets of extracellular vesicles.     

Sigma complexes in the pyrimidine series. 2. σ Complexes of 5-nitropyrimidine and methoxy-substituted 5-nitropyrimidines with the acetone anion

The corresponding σ complexes of the Meisenheimer type, viz., anions of the potassium salts of 6H-5-nitro-6-acetonylpyrimidines, were obtained and isolated in the reaction of 5-nitro-, 5-nitro-4-methoxy-, 5-nitro-2-methoxy-, and 5-nitro-2,4-dimethoxypyrimidines with acetone in the presence of potassium hydroxide. The structures of the complexes were proved by means of the PMR, IR, and UV spectra. It is shown that the acetone anion in all cases adds to the methoxy-unsubstituted position of the pyrimidine ring, whereas nucleophilic attack takes place at the C₄ atom when the 2 and 4 positions are free. See [1] for communication 1. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–242, February, 1980.     

Synthesis of β-Aminophosphonates and Study of Their Acid-Base Properties and Phase Distribution in Water-Organic Solvent Systems

New and previously known β-aminoethylphosphonates were synthesized by addition of primary and secondary amines to vinylphosphonates, and their IR and NMR spectra were examined. Diethyl 2-diethylaminoethylphosphonate and diethyl 2-morpholinoethylphosphonate were found to be stronger bases than the corresponding aminomethylphosphonates, but all these are weaker bases than their precursors, nonphosphorylated amines. Distribution constants of β-aminophosphonates between water and some organic solvents were determined and compared with those of their α-amino homologs.     

Membrane Transport of Inorganic Acids with α- Aminophosphoryl Compounds

Transport of some inorganic acids (HCl, HBr, HClO₄, HNO₃, H₂SO₄, and H₂PO₄) through hydrophobic impregnated membranes with aminophosphoryl compounds of the general formula R ₂ ¹ P(O)CH₂ ⋅ NR²R³ [R¹ = C₄H₉(C₂H₅)CHCH₂O, R² = C₄H₉, R³ = C₈H₁₇; R¹ = R³ = C₈H₁₇, R² = H; R¹ = C₁₀H₂, R² = R³ = C₂H₅; R¹ = C₁₀H₂₁, R² + R³ = (CH₂)₂O(CH₂)₂; R¹ = C₈H₁₇, R² = H, R³ = 2-quinolyl] and dodecylamine as carriers was studied. The membrane phases were solutions of the carriers in phenylcyclohexane and tridecane. General regularities that correlate the structure of an aminophosphoryl compounds to its transport properties toward inorganic acids were established. The largest flows are characteristic of perchloric, nitric, and hydrobromic acids.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005, pp. 575–578.Original Russian Text Copyright © 2005 by Garifzyanov, Shirshova, Cherkasov.     

Reaction of Organoelement Hydrides R<Subscript>3</Subscript>EH (E = Si,Ge) with Metal <Emphasis Type="Italic">tert</Emphasis>-Butylate (M = Al,Ti)-<Emphasis Type="Italic">tert</Emphasis>-Butyl Hydroperoxide Oxidative Systems

Trialkyl(aryl)silanes and -germanes effectively react with metal (Al, Ti) tert-butylate-tert-butyl-hydroperoxide under mild conditions (room temperature, benzene or tetrachloromethane) mainly by the element-hydrogen bond. The character of the products depends on the nature of the element, the structure of the radical bound to it, and the solvent. The process is radical in nature. It includes the stages of formation of element-centered radicals and their reaction with the oxygen generated by the system. The intermediate organometallic peroxides can also acts as oxidants for the element (Si, Ge)-hydrogen bonds.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1161–1170.Original Russian Text Copyright © 2005 by Stepovik, Gulenova, Martynova, Skvortsov, Cherkasov.     

Synthesis,Structure, and Hydrophosphorylation of π-Complexes of Hexacarbonyltungsten(0) with Cyclohexanone,Cyclohexanethione, and <Emphasis Type="Italic">N</Emphasis>-Cyclohexylideneaniline

New carbonyl π-complexes of tungsten(0) with cyclohexanone, cyclohexanethione, and N-cyclo-hexylideneaniline were synthesized. Geometric and electronic parameters of the ligands, as well as energy parameters of the complex formation process, were determined by quantum-chemical calculations. Hydrophosphorylation with diethyl phosphonate changed the reactivity of coordinated N-cyclohexylideneaniline, while no analogous effect was observed for cyclohexanone and cyclohexanethione.     

Electronegativity in Quantum Chemistry

The possibility is discussed for determination of chemical potential (electronegativity) of an electron-nucleus system in terms of the quantum-mechanical density functional theory (DFT). The principle of complete leveling of chemical potentials of natural orbitals, formulated in the framework of DFT, cannot be regarded now as justified. The calculation of electronic chemical potential via difference schemes still remains the only procedure suitable for estimation of this quantity by quantum-chemical methods.     

Reaction of zirconium alkoxides with tert-butyl hydroperoxide. Oxidative ability of the Zr(OBu-t)4-t-BuOOH system

Oxidation of the isopropoxy group in the Zr(i-PrO)₄·i-PrOH complex involves both direct reaction with tert-butyl hydroperoxide and intermediate formation of zirconium peroxy compound. Zirconium tetra-tert-butoxide reacts with tert-bytyl hydroperoxide to form metal-containing peroxide and trioxide. Decomposition of the latter leads to oxygen evolution and is accompanied by radical formation. The alkoxyl and peroxyl radicals formed were identified by ESR spectroscopy. The nature of the oxidant (oxygen, zirconium-containing peroxide and-trioxide) in the Zr(OBu-t)₄-t-BuOOH system is determined by the structure of the substrate molecule.     

Partition constants of α-aminophosphonates in two-phase aqueous-organic solvent systems

Two-phase potentiometric titration was used to determine partition constants for a series of -aminophosphonates (RO)₂P(O)CH₂NR¹R² [R = Alk (C₂-C₅), R¹, R² = Me, Et, (CH₂)₅] between water and organic solvents, such as chloroform, carbon tetrachloride, toluene, octane, n-octanol, nitrobenzene, o-xylene, and cyclohexane. Correlations between the partition constants and the number of carbon atoms in substrate molecules were obtained. Solvent effects on partition constants were discussed, and solution parameters of -aminophosphonates were calculated.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 12, 2004, pp. 1998–2002.Original Russian Text Copyright © 2004 by Garifzyanov, Nuriazdanova, Zakharov, Cherkasov.This revised version was published online in April 2005 with a corrected cover date.