Optimization of reaction time for detection of organophosphorus pesticides by enzymatic inhibition assay and mathematical modeling of enzyme inhibition.

Enzyme inhibition assay was used as a biomarker for detection of organophosphates pesticides in food and environmental samples. The aim of the present study was to optimize the time of enzyme-inhibitor reaction for quantitative determination of fenitrothion organophosphate based on cholinesterase inhibition. The results showed that this method provides a time-efficient, best linearity and simple assay. The effect of reaction time on the linearity relationship of the noncompetitive inhibition equation was studied. The best linearity of the assay was found at an optimum reaction time of 3.0 min, with coefficient of determination r 2 of 0.9972, in the range of inhibitor concentrations from 0.016 to 2.0 µg mL-1. The enzyme inhibition reached a plateau at 5 min by addition of pesticide in vitro and then the inhibited enzyme reactivate spontaneously and approached steady state at 20 min. A theoretical kinetic model to explain the effect of reaction time on the enzyme inhibition by addition of pesticide in vitro was derived. The higher values of coefficient of determination r 2 for the predicted model and error functions of the minimum deviations suggest that this model can be used to represent the experimental data and explain the plasma cholinesterase inhibition by fenitrothion pesticide.

Validation and kinetic of enzymatic method for the detection of organophosphate insecticides based on cholinesterase inhibition.

Kinetic and validation of the enzymatic method for the determination of fenitrothion organophosphorus based on cholinesterase inhibition were studied. A Linear relationship was obtained with a determination coefficient R2 of 0.9989 suggesting that the noncompetitive inhibition kinetic equation is suitable to represent the enzymatic assay of fenitrothion. The value of the inhibition constant KI was 0.374 µg/ml/min. The analytical logarithmic curve for the determination of fenitrothion concentration using the percentage of cholinesterase inhibition presented good linear relations at concentrations of 0.05-2 µg/ml (R2 = 0.9889). The maximum inhibition 83% was observed at 2.0 µg/ml final assay concentration. The lower inhibition 3.3% was observed at 0.05 µg/ml detection limit. The experimental measurement condition was optimized. The enzymatic method exhibited detection limits (LOD) in the range of 0.05-2.0 µg/ml. The limit of quantification (LOQ) was 0.06 µg/ml with inhibition 13%. The concentration of fenitrothion that inhibited the hydrolysis of substrate by 50% (IC50 value) was 0.4 µg/ml. Standard deviations and coefficients of variation indicate a good precision of the enzymatic method for the detection of organophosphate insecticides at an incubation time of 20 min.

Structural Characterization of Gallbladder Stones Using Energy Dispersive X-ray Spectroscopy and X-ray Diffraction.

AIM AND OBJECTIVE: Formation of the gallbladder stones is a common disease and a major health problem. The present study aimed to identify the structures of the most common types of gallbladder stones using X-ray spectroscopic techniques, which provide information about the process of stone formation. MATERIAL AND METHOD: Phase and elemental compositions of pure cholesterol and mixed gallstones removed from gallbladders of patients were studied using energy-dispersive X-ray spectroscopy combined with scanning electron microscopy analysis and X-ray diffraction. RESULTS: The crystal structures of gallstones which coincide with standard patterns were confirmed by X-ray diffraction. Plate-like cholesterol crystals with laminar shaped and thin layered structures were clearly observed for gallstone of pure cholesterol by scanning electron microscopy; it also revealed different morphologies from mixed cholesterol stones. Elemental analysis of pure cholesterol and mixed gallstones using energy-dispersive X-ray spectroscopy confirmed the different formation processes of the different types of gallstones. CONCLUSION: The method of fast and reliable X-ray spectroscopic techniques has numerous advantages over the traditional chemical analysis and other analytical techniques. The results also revealed that the X-ray spectroscopy technique is a promising technique that can aid in understanding the pathogenesis of gallstone disease.

Radiation-induced grafting of glycidyl methacrylate onto cotton fabric waste and its modification for anchoring hazardous wastes from their solutions.

Ion exchange adsorbents based on cellulosic fabric wastes carrying sulfonic acid and amine functional groups were synthesized by radiation-induced graft polymerization of glycidyl methacrylate (GMA) with subsequent chemical modification of the epoxy groups of poly-GMA graft chains with sodium sulfite/H(2)SO(4) and triethylamine, respectively. The conversion of epoxy groups into the functional groups was investigated. Factors affecting on grafting process such as radiation dose, monomer concentration and solvent were studied. The synthesized adsorbent and its applications in the removal of different types of hazardous pollutants e.g. acidic dye, cobalt, dichromate and phenols from aqueous solution were also studied.

Clinical findings and cholinesterase levels in children of organophosphates and carbamates poisoning.

INTRODUCTION: Exposure to organophosphate and carbamate insecticides inhibits cholinesterase activity and interferes with synaptic transmission both centrally and peripherally at muscarinic receptors and nicotinic receptors. The study reported the usefulness of plasma cholinesterase ChE activity assays for diagnosis and the management of organophosphate and carbamate toxicity in children. METHODS: A retrospective study was conducted on children with organophosphate and carbamate poisoning. Forty-seven patients were included. The diagnosis was confirmed by measuring plasma cholinesterase levels. Atropine was given intravenous (0.02 mg/kg) and repeated until secretions were controlled. Obidoxime chloride was administered as 4-8 mg/kg/dose for children with organophosphate poisoning and to those in whom the ingested material was unidentified on admission. DISCUSSION: Most of the patients showed marked reactivation in plasma ChE within several hours and recovered completely within 24 h of admission. Complications were observed in 17 patients (36%). Mechanical ventilatory support was required in six patients. The duration intensive care stay was 3 +/- 2.4 days. CONCLUSION: Low plasma ChE levels support the diagnosis of insecticides poisoning, but no significant association is present between the severity of poisoning and plasma ChE levels. Atropine should be used as soon as possible to counteract the muscarinic effects. Appropriate management and early recognition of the complications may decrease the mortality rate.

A study on electron impact mass spectrometry of epoxy methylated fullerenols.

Mass spectra of the epoxy methylated[60]fullerenols were obtained by EI mass spectrometry using "desorption" or "in-beam" technique. The mass spectra have an intense molecular monocation peak M(+) and a weak dication peak M(++), revealing the stability of these products under the MS (EI) conditions. The remaining peaks correspond to the successive loss of methyl groups and oxygen atoms for which the pure fullerene represents a more stable product. The distinction between the multiply charged fullerene C(60)(z+) and their fragments with equal m/z was also studied.

Identification of some polymeric materials by low-temperature pyrolysis mass spectrometry.

The application of low-temperature pyrolysis mass spectrometry to the identification of some commercial and synthetic polymers using a direct insertion probe and electron ionization has been studied. The polymers were analyzed directly in the solid probe of a mass spectrometer within the ion source at 70 eV electron impact. The quadrupole mass spectrometer, equipped with a gas chromatogram software and library of low molecular weight compounds, was used to characterize the polymers by measuring the chemical structure of the repeat units and the end groups, and to examine the thermal degradation pathways. The polymers investigated show different degradation pathways. Investigation of sequences and determination of composition of copolymers were studied. Total ion pyrogram and spectrum subtractions were used to separate and measure spectra of pyrolysis steps at distinctly different temperatures.