Improvement of acetylcholinesterase-based assay for organophosphates in way of identification by reactivators

Organophosphates present serious fulmination in several aspects of human life. Detection of organophosphates is frequently based on following acetylcholinesterase (AChE) inhibition. Although limit of detection and sensitivity for AChE-based assays seem to be intriguing, the identification of organophosphates is not currently efficient in this way. We introduce an improvement of AChE-based assay by reactivators using a selective come-back of AChE activity after previous inhibition. We have chosen four organophosphates: paraoxon-ethyl, paraoxon-methyl, trichlorfon, methamidophos as representative pesticides and the three most available reactivators: HI-6, obidoxime, pralidoxime. Reactivation was realized in the 96-wells photometric microplates and activity of human recombinant AChE was followed by reaction of Ellman's reagent with one of enzyme digestion product: thiocholine. Distinguishing of reactivation efficacy was judged by the independent two population t-test. The most significant identification was based on methamidophos inhibited AChE reactivation by HI-6 or pralidoxime and paraoxon-ethyl inhibited AChE by obidoxime; moreover, identification of trichlorfon and paraoxon-methyl was possible, too. Practical impact of described method is discussed.     

Determination of nitrous acid in air using wet effluent diffusion denuder-FIA technique

A sensitive and fast method for the determination of nitrous acid (HONO) in air is described. The method combines a continuous collection of nitrous acid into a thin film of absorption liquid in a cylindrical wet effluent diffusion denuder (CWEDD) and on-line analysis of collected nitrous acid at the denuder concentrate employing a flow-injection analysis (FIA) where nitrous acid is oxidized into peroxynitrous acid and a chemiluminescent light emitted during the reaction of peroxynitrite with luminol is detected. Various absorption solutions (carbonate, bicarbonate, phosphate) as well as deionized water were compared from point of view of collection efficiency of nitrous acid at the CWEDD and selectivity and sensitivity of nitrous acid determination in air.All tested liquids provide quantitative collection of HONO in the CWEDD at the air flow rate of 1 L min⁻¹. The detection limit of nitrous acid of 15 ppt (v/v) is the same for all tested liquids. Small positive interference of nitrogen dioxide and peroxyacetylnitrate has been found. The lowest interference of NO₂ was found for 1 × 10⁻⁴ M NaHCO₃ (pH 6.4; 0.18%) while for deionized water interference of NO₂ (0.28%) was slightly higher. The lowest interference of peroxyacetylnitrate was found for deionized water (1.46%). No enhanced formation of HONO inside the cylindrical wet effluent diffusion denuder was observed for simultaneous bringing of nitrogen dioxide together with phenol, p-cresol, guaiacol, catechol, o-nitrophenol as well as with n-octane, n-nonane, n-decane, isoprene, α-pinene, β-pinene, camphene, 3-carene, α-phellandrene, S-limonene, benzene, toluene or o-xylene in comparison with formation of HONO only in the presence NO₂.Deionized water was chosen as the optimum absorption liquid for the sampling of atmospheric nitrous acid at the CWEDD as well as for FIA chemiluminescent detection. The time resolution is 70 s and the response time is 164 s. The calibration curve is linear over 4 orders of magnitude (0.045-450 ppb HONO). The CWEDD-FIA technique has been applied to the measurement of nitrous acid in urban air.     

Multiobjective optimization of credit capital allocation in financial institutions

The evolution of international regulation leads to new capital requirements imposed on globally active companies. Financial services firms allocate capital to business lines in order to withstand the materializing credit losses and to measure the performance of various business lines. In this study, we introduce a methodology for optimal credit capital allocation based on operations research approach. In particular, we focus on the efficient allocation of capital to business lines characterized by credit risk losses and cost of capital. We compare different allocation methods and provide a rationale behind using the OR approach. Finally, we formulate a multiobjective optimization model to capital allocation problem and apply it to a real-world case of two financial conglomerates.     

A Highly Reactive Geminal P/B Frustrated Lewis Pair: Expanding the Scope to C−X (X=Cl,Br) Bond Activation

The geminal frustrated Lewis pair tBu₂PCH₂B(Fxyl)₂ ( 1 ; Fxyl=3,5‐(CF₃)₂C₆H₃) is accessible in 65 % yield from tBu₂PCH₂Li and (Fxyl)₂BF. According to NMR spectroscopy and X‐ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P ??? B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H₂, EtMe₂SiH, CO₂/CS₂, Ph₂CO, and H₃CCN. Terminal alkynes react with heterolysis of the C?H bond. Haloboranes give cyclic adducts with strong P?BX₃ and weak R₃B?X bonds. Unprecedented transformations leading to zwitterionic XP/BCX₃ adducts occur on treatment of 1 with CCl₄ or CBr₄ in Et₂O. In less polar solvents (C₆H₆, n‐pentane), XP/BCX₃ adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph₂CO with EtMe₂SiH.     

Applying Mechanochemistry for Bottom‐Up Synthesis and Host–Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water‐Soluble β‐Cyclodextrin‐Coated Zinc Oxide

Mechanochemistry has recently emerged as an environmentally friendly solventless synthesis method enabling a variety of transformations including those impracticable in solution. However, its application in the synthesis of well‐defined nanomaterials remains very limited. Here, we report a new bottom‐up mechanochemical strategy to rapid mild‐conditions synthesis of organic ligand‐coated ZnO nanocrystals (NCs) and their further host–guest modification with β‐cyclodextrin (β‐CD) leading to water‐soluble amide‐β‐CD‐coated ZnO NCs. The transformations can be achieved by either one‐pot sequential or one‐step three‐component process. The developed bottom‐up methodology is based on employing oxo‐zinc benzamidate, [Zn₄(μ₄‐O)(NHOCPh)₆], as a predesigned molecular precursor undergoing mild solid‐state transformation to ZnO NCs in the presence of water in a rapid, clean and sustainable process.     

Incorporation of a Phenanthrene Subunit into a Sapphyrin Framework: Synthesis of Expanded Aceneporphyrinoids

32‐Hetero‐5,6‐dimethoxyphenanthrisapphyrins—macrocycles that link structural features of polycylic aromatic hydrocarbons and expanded porphyrins—were obtained in a straightforward [3+1] condensation reaction of dimethoxyphenanthritripyrrane and 2,5‐bis(arylhydroxymethyl)heterocyclopentadienes. The highly folded conformation of formally 4 n π‐electron macrocycles causes them to manifest only limited macrocyclic π conjugation as explored by means of NMR spectroscopic and X‐ray structural analyses, and supported by DFT calculations. Although protonation does not change their π‐conjugation characteristics, the cleavage of ether groups at the phenanthrenylene moiety yields nonaromatic 32‐hetero‐5,6‐dioxophenanthrisapphyrins.     

Heat kernel estimates for the Bessel differential operator in half‐line

In the paper we consider the Bessel differential operator in half‐line , , and its Dirichlet heat kernel . For , by combining analytical and probabilistic methods, we provide sharp two‐sided estimates of the heat kernel for the whole range of the space parameters and every , which complements the recent results given in 1 , where the case was considered.     

Targeted synthesis of 1-(4-hydroxyiminomethylpyridinium)-3-pyridiniumpropane dibromide--a new nerve agent reactivator

Preparation of 1-(4-hydroxy-iminomethylpyridinium)-3-pyridiniumpropane dibromide is described. This compound represents a new acetylcholinesterase (AChE) reactivator, which has no substituents on the second pyridinium ring as found in other commonly used AChE reactivators. The reactivation ability of this reactivator was tested on tabun- and cyclosarin-inhibited AChE. According to the results obtained, the new compound (without substitution and with decreased molecule size) showed increased reactivation potency in case of cyclosarin inhibited AChE. A potent oxime for treatment of tabun and cyclosarin-caused intoxications was thus obtained via slight modification of the reactivator structure (compared to trimedoxime and K027).