Zbyněk Kobliha

Reactivation of Immobilized Acetylcholinesterase–Tabun Complex by Methoxime and Its Homologues

Using an immobilized acetylcholinesterase–tabun enzyme–inhibitor complex, the reactivation efficacy of a homologous series of bispyridinium reactivators with increasing length of the alkylene chain between the pyridinium rings has been studied. The number of the alkylene groups in the chain ranged from one to six. N,N′-Monomethylenebis(4-pyridiniumaldoxime) dibromide (MMB-4) and N,N′-trimethylenebis(4-pyridiniumaldoxime) dibromide (TMB-4) are the most efficient reactivators of the series.

Reactivation of immobilized acetylcholinesterase‑tabun complex by pralidoxime, its isomers, and homologs

Reactivation efficacy of three homologous and three isomeric series of pralidoxime-type reactivators with aldoxime group in position 2, 3 and 4 of the heterocycle was tested in reactivation of tabun-inhibited AChE. The experiments were performed with immobilized and stabilized porcine brain AChE. The enzyme acticity was measured by Ellman method. Reactivation efficacy was determined by measurement of indicator fabric coloration intensity as a measure of AChE activity. Of the studied group of nine reactivators, isomers with the functional group in position 2 were the most effective. The highest value (30 %) for reactivation of inhibited AChE was found for 2PAE after treatment for 15 min at concentration 0.5 mg/cm3. The efficacy of the isomers decreased in the order ortho > para > meta. No marked effect on the efficacy of the reactivators was observed on prolongation of the reactivation time. The reactivators efficacy decreased with decreasing concentration of their solutions.

A SIMPLE COLORIMETRIC DETECTOR OF SYMMETRIC 2-(DIALKYLAMINO)ETHANETHIOLS AS PRECURSORS OF V-TYPE NERVE AGENTS

A colorimetric detector tube of 2-(dialkylamino)ethanethiols as precursors of V-type nerve agents and their hydrolytic products was designed. The detector is based on a reaction of 2-(dialkylamino)ethanethiols with a chromogenic reagent 4-chloro-7-nitrobenzofurazan (NBD-Cl) in alkaline medium leading to characteristic coloured products. The detection limit in water is of 5 μg/ml, the optimum measurement range being up to 250 μg/ml. The detector also presented a response to some other warfare chemical agents, the colour shade being, however, different. Effects of disturbing substances and organic solvents were studied.

Efficacy of 2-PAM, TMB-4, HI-6, and Toxogonin in Reactivation of Immobilized Acetylcholinesterase Inhibited by Compound R-33

ABSTRACT Efficacy of reactivators 2-PAM, TMB-4, HI-6, and toxogonin in reactivation of acetylcholinesterase inhibited by compound R-33 has been studied. The study was performed with acetylcholinesterase immobilized and stabilized on a cotton fabric and with an indicator paper with acetylthiocholine iodide and 5,5′-dithiobis(2-nitrobenzoic acid). The enzyme activity was determined by measurement of remission changes of the fabric surface, caused by reaction of the chromogenic reagent with products of enzymatic hydrolysis of the substrate. The most potent of the reactivators studied was 2-PAM at concentrations 0.5 mg.cm−3 and 0.1 mg.cm−3. Effectivity of this reactivator was over 20%. At these concentrations, reactivator HI-6 was less effective. Efficacy higher than that of 2-PAM was observed only after 20 min at concentrations 0.05 mg.cm−3 and 0.01 mg.cm−3. For TMB-4 and toxogonin the reactivation values were about 10% after 10 min, whereas after 15 or 20 min these reactivators were ineffective.

Pellet patented technology for fast and distinct visual detection of cholinesterase inhibitors in liquids

Graphical abstract Figure. No Caption available. HighlightsDouble‐coated pellets for detection of cholinesterase inhibitors were prepared.Lower amount of enzyme for a formulation of the detection system was needed.A more distinctive color transition during the detection in liquids was achieved. ABSTRACT The main objective of the presented research was to prepare an innovative carrier as a filler for detection tubes in the form of double‐coated pellets with a very significant color transition during the detection of cholinesterase inhibitors such as nerve agents, organophosphorus or carbamate insecticides in liquids that is observable visually and also spectrophotometrically at 412 nm. The pellet cores were prepared by the extrusion/spheronization method. Consecutively, two different coats were applied on the pellet cores in the coating device using the Wurster column method. To increase the color change intensity, the second semipermeable coat based on Eudragit® RL was applied on top of the first coat, which was formed by butyrylcholinesterase immobilized in hydroxypropyl methylcellulose. Prepared samples differing in thickness of the second coat were evaluated for their quality parameters, enzymatic activity and inhibition. The detection mechanism was based on the standard Ellman’s colorimetric reaction. It was observed that the semipermeable coat prevented leaching of the enzyme into the solution and led to an increased intensity of color transition from white – yellow to white – deep yellow/orange, thus enabling a more accurate visual detection. This system allows easy, rapid and safe identification of cholinesterase inhibitors in liquids, especially chemical warfare agents.

New detector tube for the detection of nitrite in water

Abstract A new colorimetric detector tube for the detection of trace concentrations of nitrite in water was developed. The detector tube is based on a diazo coupling reaction of nitrite with dapsone and N-(1-naphthyl) ethylenediamine dihydrochloride during the formation of red-violet azo dye. Spherical granules (pellets) made from the composite material were used as the carrier of chemical reagents. They were prepared by pelletizing the mixture of microcrystalline cellulose, lactose, kaolin and polyvinylpyrrolidone. Colouring is done on a layer of silica gel impregnated with citric acid. The detector tube is highly sensitive, selective and stable when stored. The detection limit is 0.1 μg.ml-1, i.e. 0.03 μg.ml-1 N(NO2 -). The optimal measuring range of nitrite concentration in the analyzed sample ranges from 0.5 to 80 μg.ml-1, i.e. 0.15-24.36 μg.ml-1 N(NO2 -). The detector tube can easily be structurally modified for analysis of nitrates with a detection limit of 1 μg/ml-1, i.e. 0.23 μg.ml-1 N(NO3 -).