Flow-injection determination of water-soluble vitamins B1, B2, and B6 from the electrocatalytic response of a graphite electrode modified with a ruthenium(III) hexacyanoruthenate(II) film

The electrochemical behavior of water-soluble vitamins B₁, B₂, and B₆ at an unmodified graphite electrode and a graphite electrode modified with an inorganic film of ruthenium(III) hexacyanoruthenate(II) was studied. The electrocatalytic activity of the metal complex in the oxidation of vitamins was found. Ru(IV) species act as a catalyst. Conditions for recording voltammograms and hydrodynamic conditions for detecting the maximum catalytic current in flow-injection analysis (FIA) were selected. Procedures for the amperometric detection of thiamine, riboflavin, and pyridoxine were proposed.     

Study of the conformations of some α-hydroxy and α-methoxy ketones

Conclusions Using the methods of dipole moments and the Kerr effect, it was found that the methoxy group in -methoxyacetone (regardless of the conformational state with respect to the C-C bond) is oriented in the direction of the carbonyl group. The orientation and conformation of the hydroxyl group in - and -hydroxy-4-caranones were determined and compared with the conformations of the corresponding methoxy derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2208–2212, October, 1987.     

Synthesis,transport, and ionophore properties of α,ω-bisphosphorylated azapodands: IX. Extraction of metal ions with quasiliquid emulsions on the basis of N,N′-bis(dioctylphosphorylmethyl)-1,8-diamino-3,6-dioxaoctane and acidic components

Processes of extraction of ions of the I–IV group metals from acidic water solutions with paraffin quasiliquid emulsions containing neutral phosphorylazapodand, bis(dioctylphosphorylmethyl)-1,8-diamino-3,6-dioxaoctane I, and acidic components, bispentadecylphosphoric II and hexadecylsulfonic acid III is studied. High effectiveness of extraction of metal ions with these extraction compositions is established. It significantly exceeds the effectiveness of liquid extraction in the same systems, especially of ions of the II group metals. The extraction of three-charged ions proceeds more effectively by the mixture of organophosphorus reagents I and II, than with the composition consisting of azapodand I and organosulfur acid III.     

Acetylcholinesterase Sensor Based on Polyelectrolyte Complexes with DNA Inclusion for the Determination of Reversible Inhibitors

The acetylcholinesterase (AChE) biosensor has been developed for the determination of reversible inhibitors applied in the Alzheimer's disease therapy, i. e., Huperzine A (HupA) and galantamine (Gal). For this purpose, glassy carbon electrode (GCE) was first modified with carbon black (CB) and Co phthalocyanine and then polyelectrolyte complex was self‐assembled on its surface by drop casting of reactants and washing. To extend the stability and improve biosensor performance, it was proposed for the first time to use DNA as polyanion in the complex assembly. The DNA showed higher charge density than conventional polyelectrolytes and stabilized the surface coating by adsorption of higher enzyme amount and prevention of its leaching during the biosensor operation. Complex formation and the influence of structural factors were monitored with surface plasmon resonance. Kinetic study showed mixed inhibition of the enzyme within micro‐ and nanomolar range of inhibitor concentrations. The AChE biosensor showed limit of detection of HupA equal to 0.9 and that of Gal to 70 nM. The sensitivity of drug determination was found to be close or better than that of the AChE biosensors previously reported in the literature. The biosensor was tested on the sample of artificial urine and showed 102 % recovery of the drugs determination.     

Synthesis of α-hydroxy(polyprenyl) bisphosphonates

Bisphosphonates derived from natural terpenes were synthesized by phosphonylation of corresponding aldehydes. The general strategy of introduction of the phosphonate groups into the polyprenol molecule involves successive treatment of a hydroxyl compound by Swern reagent to oxidize the C-OH group into C=O and a (EtO)₃P/[PyH]⁺ClO _? ⁴ mixture to phosphylate the resulting carbonyl compound.     

On commuting differential operators of rank 2

We study examples of formally self-adjoint commuting ordinary differential operators of order 4 or 4g + 2 whose coefficients are analytic on ?. We prove that these operators do not commute with the operators of odd order, justifying rigorously that these operators are of rank 2.     

Conformational investigation of phenoxycyclohexan-2-one andp-Cl- andp-NO2-phenoxycyclohexan-2-one by molecular mechanics; x-ray crystallographic analysis ofp-NO2-phenoxycyclohexan-2-one

The preferred conformers of phenoxycyclohexan-2-one and p-Cl- andp-NO₂-phenoxycyclohexan-2-ones were calculated by the MM2(87) method. The results are compared with the data from experimental conformational investigations in solution. According to the calculation, the compounds are described by a multicomponent equilibrium, including thesp-G conformer with a planar orientation of the anisole fragment and a mixture of theac-G andT conformers both with planar and with orthogonal arrangement of the aryl group. The structure ofsp-G(0°)p-NO₂-phenoxycyclohexan-2-one was determined by x-ray crystallographic analysis.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1359–1364, June, 1992.     

Two-dimensional superionic conductors CuCrS2 and AgCrS2 and their alloys

The structural peculiarities of CuCrS₂ and AgCrS₂ and the phase ratios in the alloys Cu _x Ag_1?x CrS₂ (x = 0–1) of these compounds were studied at 293–773 K. CuCrS₂ was shown to have unlimited solubility in AgCrS₂ in disordered phases. Ion conductivity was measured for all compositions. At the phase transition point, the activation energy of ion conductivity changed abruptly. The chemical diffusion coefficients and ion transport numbers were determined from the set-in and decay curves of concentration polarization.     

Synthesis, transport and ionophore properties of α,ω-biphosphorylated azapodands: V. Acid-base properties of new phosphorylated azapodands and α,ω-diamines and their participation in the membrane transport of I–III groups metal ions

Acid-base properties of newly and previously synthesized phosphorylated azapodands and ??,??-diamines and their amine precursors were studied. We found that they differ in the same range as has been found previously for the other aminophosphoryl compounds. The investigation of the processes of passive membrane ion transport of a series of metals of I?CIII groups by these reactants showed with all diphosphoryl diamines higher values of the transfer flow of the ions Sc(III), Nd(III), and Sm(III), than the ions of alkali and alkaline earth metals. Under the conditions of active membrane transport the azapodand IV exhibits high efficiency in the ion transport of Sr(II) and Ba(II), while diphosphoryldiamine III exhibits effective transport of Nd(III) ions. The factors that determine the efficiency and selectivity of the membrane extraction of the I?CIII groups metal ions by these diphosphoryl diamines are discussed.