Study of the Process $${e}^{{+}}{e}^{{-}}{\to}{\eta\pi}^{{0}}{\gamma}$$ in the Cossision-Energy Range of $$\sqrt{{s}}{=}{1.05{-}2.00}$$ GeV

Physics of Atomic Nuclei - The process $$e^{+}e^{-}\to\eta\pi^{0}\gamma$$ is studied in the range of center-of-mass (c.m.) collision energies between 1.05 and 2.00 GeV on the basis of data...     

Room-temperature synthesis of pharmaceutically important carboxylic acids bearing the 1,2,4-oxadiazole moiety

An efficient and mild one-pot protocol has been developed for the synthesis of 1,2,4-oxadiazoles via the reaction of amidoximes with dicarboxylic acid anhydrides in a NaOH/DMSO medium. The method allows the synthesis of diversely substituted carboxylic acids bearing the 1,2,4-oxadiazole motif, – a popular building block for pharmaceutical research, in moderate to excellent yields. The reaction scope includes aromatic and heteroaromatic amidoximes as well as five-, six- and seven-membered anhydrides. The advantages of this procedure are proven gram-scalability and the use of inexpensive starting materials, which from a process chemistry point of view are essential for future industrial applications.     

Modeling of electrochemical processes in solid oxide fuel cells

A mathematical model of electrochemical processes in a solid oxide fuel cell is presented. A procedure for the calculation of the current—voltage characteristic (CVC) taking into account the influence of the reagent concentration, pressure, and temperature is considered. The problem of calculation of the electromotive force (emf) and thermodynamic efficiency was studied in detail. The influence of the presence of carbon dioxide and water vapor in the anode gas on the emf and thermodynamic efficiency is analyzed. The method of measuring the CVC in an experiment at a constant fuel rate is briefly considered. The results of application of the calculation model are compared with the experimental data.     

DSC investigation of oxygen subsystem in Ba-Y-Cu-O superconductors

DSC investigations have been performed for a series of compounds Ba₂YCu₃O_y with the oxygen content varying in the rangey=6.0...6.9 by means of various heat treatments at 800–1200 K followed by quenching, or through the chemical extraction of oxygen by placing the sample in dihydrogen at 470–490 K. The sample preserving a constant oxygen content during heating in nitrogen exhibited exothermal effects between 450 and 850 K. It has been shown that the H vs. y function reaches maximum aty 6.5. Kinetic measurements have shown that the diffusive mobility of oxygen atoms in the lattice is responsible for these effects, viz. the Arrhenius and cooperative processes of reorganization in the non-equilibrium oxygen subsystem of the bulk.

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Zusammenfassung Für eine Reihe von Verbindungen der allgemeinen Formel Ba₂YCu₃O_y und einem Sauerstoffgehalt vony=6.0....6.9 wurden mittels verschiedener Wärmebehandlungen bei 800–1200 K, gefolgt durch Abschrecken oder beim chemischen Sauerstoffentzug durch Einbringen der Probe in Diwasserstoff bei 470–490 K DSC-Untersuchungen durchgeführt. Wird die Probe in Stickstoff erhitzt, so behält sie ihren Sauerstoffgehalt bei und zeigt bei 450–850 K einen exothermen Effekt. Es wurde gezeigt, daß die Funktion H(y) bei etwa y=6.5 ein Maximum erreicht. Kinetische Messungen zeigen, daß für diesen Effekt die diffusive Beweglichkeit der Sauerstoffatome im Gitter verantwortlich ist.

     

Cyclometallated Platinum(II) Complexes for Obtaining Phenyl-Containing Silicone Rubbers via Catalytic Hydrosilylation Reaction

Russian Journal of General Chemistry - C,N-Chelate deprotonated diaminecarbene platinum(II) complexes were studied as polysiloxane system hydrosilylation catalysts. Phenyl-containing silicone...     

Good-Practice Non-Radioactive Assays of Inorganic Pyrophosphatase Activities

Inorganic pyrophosphatase (PPase) is a ubiquitous enzyme that converts pyrophosphate (PP_i) to phosphate and, in this way, controls numerous biosynthetic reactions that produce PP_i as a byproduct. PPase activity is generally assayed by measuring the product of the hydrolysis reaction, phosphate. This reaction is reversible, allowing PP_i synthesis measurements and making PPase an excellent model enzyme for the study of phosphoanhydride bond formation. Here we summarize our long-time experience in measuring PPase activity and overview three types of the assay that are found most useful for (a) low-substrate continuous monitoring of PP_i hydrolysis, (b) continuous and fixed-time measurements of PP_i synthesis, and (c) high-throughput procedure for screening purposes. The assays are based on the color reactions between phosphomolybdic acid and triphenylmethane dyes or use a coupled ATP sulfurylase/luciferase enzyme assay. We also provide procedures to estimate initial velocity from the product formation curve and calculate the assay medium’s composition, whose components are involved in multiple equilibria.     

The Ca2+-Regulated Photoprotein Obelin as a Tool for SELEX Monitoring and DNA Aptamer Affinity Evaluation

Bioluminescent solid-phase analysis was proposed to monitor the selection process and to determine binding characteristics of the aptamer–target complexes during design and development of the specific aptamers. The assay involves Ca²⁺-regulated photoprotein obelin as a simple, sensitive and fast reporter. Applicability and the prospects of the approach were exemplified by identification of DNA aptamers to cardiac troponin I, a highly specific early biomarker for acute myocardial infarction. Two structurally different aptamers specific to various epitopes of troponin I were obtained and then tested in a model bioluminescent assay.     

Unusual Formation of 1,2,4-Oxadiazine Core in Reaction of Amidoximes with Maleic or Fumaric Esters

We have developed a simple and convenient method for the synthesis of 3-aryl- and 3-hetaryl-1,2,4-oxadiazin-5-ones bearing an easily functionalizable (methoxycarbonyl)methyl group at position 6 via the reaction of aryl or hetaryl amidoximes with maleates or fumarates. The conditions for this reaction were optimized. Different products can be synthesized selectively in good yields depending on the base used and the ratio of reactants: substituted (1,2,4-oxadiazin-6-yl)acetic acids, corresponding methyl esters, or hybrid 3-(aryl)-6-((3-(aryl)-1,2,4-oxadiazol-5-yl)methyl)-4H-1,2,4-oxadiazin-5(6H)-ones. The reaction is tolerant to substituents’ electronic and steric effects in amidoximes. As a result, a series of 2-(5-oxo-3-(p-tolyl)-5,6-dihydro-4H-1,2,4-oxadiazin-6-yl)acetic acids, their methyl esters, and 1,2,4-oxadiazoles based on them were prepared and characterized by HRMS, ¹H, and ¹³C NMR spectroscopy. The structures of three of them were elucidated with X-ray diffraction.     

Stacking Interactions: A Supramolecular Approach to Upgrade Weak Halogen Bond Donors

The co-crystallization of tetracyanobenzene (TCB) with haloarenes ArX provided six new co-crystals TCB ⋅ ArX (ArX=PhCl, PhBr, 4-MeC₆H₄Cl, 4-MeC₆H₄Br, 4-MeOC₆H₄Cl, 1,2-Br₂C₆H₄) which were studied by X-ray diffraction. In these systems, the strong collective effect of π⋅⋅⋅π stacking interactions and lone pair-(X)⋅⋅⋅π-hole-(C) bondings between TCB and ArX promote the strength of X⋅⋅⋅N_cyano halogen bonding (HaB). Theoretical studies showed that the stacking interactions affect the σ-hole depth of the haloarenes, thus significantly boosting their ability to function as HaB donors. According to the molecular electrostatic potential calculations, the σ- hole-(Cl) value (1.5 kcal/mol) in the haloarene 4-MeOC₆H₄Cl (featuring an electron-rich arene moiety and exhibiting very poor σ-hole-(Cl) ability) increases significantly in the stacked trimer (TCB)₂ ⋅ 4-MeOC₆H₄Cl (12.5 kcal/mol). Theoretical DFT calculations demonstrate the dramatic increase of X⋅⋅⋅N_cyano HaB strength for stacked trimers in comparison with parent unstacked haloarenes.