Hydrolysis Of Organophosphorus Compounds Research Articles

Ultrabright chemiluminescent scaffold for portable visualizing organophosphorus compounds

Chemiluminescence (CL) has been recognized as one of the most powerful tools in analytical assays with high signal-to-noise ratio. Ultrabright chemiluminophores are highly desired in CL-based analytical approaches, imaging, for example, although the design of CL scaffold with ultra-brightness remains a challenge. We report a feasible strategy for constructing an ultrabright chemiluminophore, BTCL-Cl, by grafting benzothiazole moiety to the dioxetane center of Schaap’s adamantylidene-dioxetane. Compared with the classical undecorated chemiluminophores, the CL quantum yield of BTCL-Cl has improved by 2.4-folds to 17.6% with a short half-life due to deprotonation under alkaline conditions. Probe CL-HMPC, the thiol-recognizer-decorated BTCL-Cl, has demonstrated ultrahigh sensitivity (detection limit is 6.0 ng/mL) in monitoring organophosphorus compounds (OPs) by immediate releasing of thiols after the alkaline hydrolysis of OPs. The OPs-triggered remarkable CL enhancement has ensured quantitively visualization of OPs in the naked eye by imaging with a smartphone in situ. Using the versatile and ultrasensitive CL platform, we succeeded in feasibly visualizing the concentration of OPs on cabbage leaves on farmland by portable setups. The simple and promising approach for analyzing pesticides and potentially other targets brings tremendous imagination in related areas.

Influence of the leaving group on the mechanism of hydrolysis of organophosphorus compounds by phosphotriesterase from bacterium Pseudomonas diminuta

Influence of the leaving group on the mechanism of hydrolysis of organophosphorus compounds by phosphotriesterase from bacterium Pseudomonas diminuta

Anti-Chemical Properties of Modular Protective Material

Previously, we developed the principle of constructing modular materials with specified properties, according to which organometallic composites, with nanoscale enzyme complexes introduced into them, are applied to a unified fabric platform. The resulting composites become a new platform for heterogeneous biocatalysis. Such a platform has high stability and good catalytic selectivity. The aim of the work is to study the properties of a unified fabric platform and to establish the possibility of giving materials (tissues) anti-chemical protective properties. The paper analyzes scientific and practical information on the production of composite fibrous materials with frame fibrous layers. The properties of a unified tissue platform and the mechanisms of protective action due to the enzymecontaining formulation applied to it are investigated. As a unified fabric platform on which other special modules are applied, it is proposed to use para-aramid protective fabric (Rusar fiber), as well as other types of fabrics – mixed aramid-viscose, aramid-cotton, aramid-polyacrylate, metaaramide (Nomex fiber). The physical properties and chemical structure of aromatic polyamides, possible directions for the production of aramid fibers, the structure and structure of aramid fibers, the mechanisms of chemical processes in polyinide compositions of various compositions are considered. Approaches to giving materials (tissues) anti-chemical protective properties are determined. The catalytic characteristics of fibrous materials functionalized by enzyme-polyelectrolyte complexes carrying out hydrolysis of organophosphorus compounds and mycotoxins have been studied.

U.S. Biowarfare Labs in Post-Soviet States

Previously, we developed the principle of constructing modular materials with specified properties, according to which organometallic composites, with nanoscale enzyme complexes introduced into them, are applied to a unified fabric platform. The resulting composites become a new platform for heterogeneous biocatalysis. Such a platform has high stability and good catalytic selectivity. The aim of the work is to study the properties of a unified fabric platform and to establish the possibility of giving materials (tissues) anti-chemical protective properties. The paper analyzes scientific and practical information on the production of composite fibrous materials with frame fibrous layers. The properties of a unified tissue platform and the mechanisms of protective action due to the enzyme containing formulation applied to it are investigated. As a unified fabric platform on which other special modules are applied, it is proposed to use para-aramid protective fabric (Rusar fiber), as well as other types of fabrics – mixed aramid-viscose, aramid-cotton, aramid-polyacrylate, metaaramide (Nomex fiber). The physical properties and chemical structure of aromatic polyamides, possible directions for the production of aramid fibers, the structure and structure of aramid fibers, the mechanisms of chemical processes in polyinide compositions of various compositions are considered. Approaches to giving materials (tissues) anti-chemical protective properties are determined. The catalytic characteristics of fibrous materials functionalized by enzyme-polyelectrolyte complexes carrying out hydrolysis of organophosphorus compounds and mycotoxins have been studied

Simultaneous Hydrolysis and Detection of Organophosphate by Benzimidazole Containing Ligand-Based Zinc(II) Complexes

The agricultural use of organophosphorus pesticides is a widespread practice with significant advantages in crop health and product yield. An undesirable consequence is the contamination of soil and groundwater by these neurotoxins resulting from over application and run-off. Here, we design and synthesize the mononuclear zinc(II) complexes, namely, [Zn(AMB)2Cl](ClO4) 1 and [Zn(AMB)2(OH)](ClO4) 2 (AMB = 2-aminomethylbenzimidazole), as artificial catalysts inspired by phosphotriesterase (PTE) for the hydrolysis of organophosphorus compounds (OPs) and simultaneously detect the organophosphate pesticides such as fenitrothion and parathion. Spectral and DFT (B3LYP/Lanl2DZ) calculations revealed that complexes 1 and 2 have a square-pyramidal environment around zinc(II) centers with coordination chromophores of ZnN4Cl and ZnN4O, respectively. Both 1 and 2 were used as a modifier in the construction of a biomimetic sensor for the determination of toxic OPs, fenitrothion and parathion, in phosphate buffer by square wave voltammetry. The hydrolysis of OPs using 1 or 2 generates p-nitrophenol, which is subsequently oxidized at the surface of the modified carbon past electrode. The catalytic activity of 2 was higher than 1, which is attributed to the higher electronegativity of the former. The oxidation peak potentials of p-nitrophenol were obtained at +0.97 V (vs. Ag/AgCl) using cyclic voltammetry (CV) and +0.88 V (vs. Ag/AgCl) using square wave voltammetry. Several parameters were investigated to evaluate the performance of the biomimetic sensor obtained after the incorporation of zinc(II) complex 1 and 2 on a carbon paste electrode (CPE). The calibration curve showed a linear response ranging between 1.0 μM (0.29 ppm) and 5.5 μM (1.6 ppm) for fenitrothion and 1.0 μM (0.28 ppm) and 0.1 μM (0.028 ppm) for parathion with a limit of detection (LOD) of 0.08 μM (0.022 ppm) and 0.51 μM (0.149 ppm) for fenitrothion and parathion, respectively. The obtained results clearly demonstrated that the CPE modified by 1 and 2 has a remarkable electrocatalytic activity towards the hydrolysis of OPs under optimal conditions.

Theoretical Studies Applied to the Evaluation of the DFPase Bioremediation Potential against Chemical Warfare Agents Intoxication.

Organophosphorus compounds (OP) are part of a group of compounds that may be hazardous to health. They are called neurotoxic agents because of their action on the nervous system, inhibiting the acetylcholinesterase (AChE) enzyme and resulting in a cholinergic crisis. Their high toxicity and rapid action lead to irreversible damage to the nervous system, drawing attention to developing new treatment methods. The diisopropyl fluorophosphatase (DFPase) enzyme has been considered as a potent biocatalyst for the hydrolysis of toxic OP and has potential for bioremediation of this kind of intoxication. In order to investigate the degradation process of the nerve agents Tabun, Cyclosarin and Soman through the wild-type DFPase, and taking into account their stereochemistry, theoretical studies were carried out. The intermolecular interaction energy and other parameters obtained from the molecular docking calculations were used to construct a data matrix, which were posteriorly treated by statistical analyzes of chemometrics, using the PCA (Principal Components Analysis) multivariate analysis. The analyzed parameters seem to be quite important for the reaction mechanisms simulation (QM/MM). Our findings showed that the wild-type DFPase enzyme is stereoselective in hydrolysis, showing promising results for the catalytic degradation of the neurotoxic agents under study, with the degradation mechanism performed through two proposed pathways.

Kinetic studies of hydroxamate and functionalized oximate ions for hydrolysis of organophosphorus compounds

Kinetic studies of hydroxamate and functionalized oximate ions for hydrolysis of organophosphorus compounds

Mechanistic insights into the hydrolysis of organophosphorus compounds by paraoxonase-1: exploring the limits of substrate tolerance in a promiscuous enzyme

We designed, synthesized and screened a library of analogs of the organophosphate pesticide metabolite paraoxon against a recombinant variant of human serum paraoxonase-1. Alterations of both the aryloxy leaving group and the retained alkyl chains of paraoxon analogs resulted in substantial changes to binding and hydrolysis, as measured directly by spectrophotometric methods or in competition experiments with paraoxon. Increases or decreases in the steric bulk of the retained groups generally reduced the rate of hydrolysis, while modifications of the leaving group modulated both binding and turnover. Studies on the hydrolysis of phosphoryl azide analogs as well as amino-modified paraoxon analogs, the former being developed as photo-affinity labels, found enhanced tolerance of structural modifications, when compared with O-alkyl substituted molecules. Results from computational modeling predict a predominant active site binding mode for these molecules which is consistent with several proposed catalytic mechanisms in the literature, and from which a molecular-level explanation of the experimental trends is attempted. Overall, the results of this study suggest that while paraoxonase-1 is a promiscuous enzyme, there are substantial constraints in the active site pocket, which may relate to both the leaving group and the retained portion of paraoxon analogs.

Hybrid proteins with organophosphorus hydrolase activity and fluorescence of deGFP4 protein

New genetic constructs encoding synthesis of hybrid proteins possessing organophosphorus hydrolase activity and properties of the pH sensitive analog of the green fluorescent protein were developed. It was established that 0.1 mM of the biosynthesis inducer and cultivation for 10 h after the induction were necessary for the maximum yield of the hybrid proteins in the soluble and active form in E. coli cells. The demonstrated synthesis level for one of the new proteins was 2- to 25-fold higher than the yield of the soluble hybrid protein analogs known from the literature. It was found that the organophosphorus hydrolase within hybrid proteins demonstrated characteristics (pH optimum, thermal stability and catalytic efficiency) different from the respective characteristics known for the native enzyme. It was shown that the fluorescence of the green fluorescent protein within the hybrid proteins depended on the pH of the medium in a manner similar to the individual protein. Interrelation of the fluorescent characteristics and OPH activity that manifested itself in the hydrolysis of organophosphorus compounds was shown by example of one of the hybrid proteins.

Hydrolysis of organophosphorus compounds by microbial enzymes

There are classes of microbial enzymes that have the ability to degrade harmful organophosphorus (OP) compounds that are present in some pesticides and nerve agents. To date, the most studied and potentially important OP-degrading enzymes are organophosphorus hydrolase (OPH) and organophosphorus acid anhydrolase (OPAA), which have both been characterized from a number of organisms. Here we provide an update of what is experimentally known about OPH and OPAA to include their structures, substrate specificity, and catalytic properties. Current and future potential applications of these enzymes in the hydrolysis of OP compounds are also addressed.

Purification and characterization of an esterase isozyme involved in hydrolysis of organophosphorus compounds from an insecticide resistant pest, Helicoverpa armigera (Lepidoptera: Noctüidae)

An esterase isozyme was purified from the insecticide resistant pest, Helicoverpa armigera collected from field crops. Purification involved ammonium sulfate precipitation, hydrophobic interaction and ion exchange chromatography followed by gel filtration chromatography. The purification was 212-fold with 1% yield of the enzyme. The optimum pH of the isozyme was found to be 10.5 and 8.5 for p-nitrophenyl phosphate and paraoxon, respectively. The enzyme was unstable at temperature >50 °C. The molecular mass determined by SDS-PAGE was 66 kDa. Cations such as Hg +2, Ag +2, Cd +2 inhibited the activity while Zn +2 stimulated it. Kinetic studies indicated that the enzyme had low K m values of 0.238 and 0.348 mM for p-nitrophenyl phosphate and paraoxon, respectively. The enzyme had broad substrate specificity with high K m values for ATP, ADP and β-glycerophosphate. This enzyme was partially sequenced and identified as an alkaline phosphatase.

Paraoxonase activity and genetic polymorphisms in greenhouse workers with long term pesticide exposure.

Serum paraoxonase (PON1) is a high-density lipoprotein (HDL) associated protein, which plays a critical role in the pathogenesis of atherosclerosis, although it was primarily associated with the hydrolysis of organophosphorus compounds. PON1 was initially thought to be independent from physiological or pathological states, although recently some environmental factors have been reported to modulate its activity. In this study, we have investigated the promoter (PON1 -108C/T and -909 C/G) and coding region (PON1 192Q/R and 55L/M) polymorphisms, as well as PON1 activity towards different substrates (paraoxon, phenylacetate and diazoxon) in 102 individuals with long term low dose exposure to pesticides in a plastic greenhouse setting (sprayers), who are probably the group of agricultural workers with the highest exposure to pesticides. PON1 activity towards paraoxon was nonsignificantly decreased (up to 53.5%) in the sprayers subgroup exposed to organophosphates (n = 41) compared with nonsprayers acting as controls (n = 39). None of the genotypes studied was associated significantly with the subgroup of individuals exposed to organophosphates, although differences between sprayers and nonsprayers were observed in the PON1 -909 G/C polymorphism. Among the environmental factors that significantly predicted lower rates of PON1 activity towards paraoxon are, interestingly, the exposure to organophosphates and current smoking. By contrast, the utilization of protective clothing while spraying pesticides inside the greenhouses was positively associated with PON1 activity, very likely by preventing the pesticides from being absorbed. This study suggests that chronic exposure to pesticides might decrease PON1 activity and pinpoints the potential usefulness of monitoring PON1 activity in occupational settings where exposure to organophosphates occurs.

Variability of the Paraoxonase Gene (PON1) in Euro- and Afro-Brazilians

The human high-density lipoprotein-associated paraoxonase (EC 3.1.1.2; PON1) plays a role in the hydrolysis of organophosphorus compounds and against the oxidative damage of low-density lipoprotein. In the present study, variants of PON1 (55 and 192) were investigated by PCR-RFLP and PCR-SSCA in Euro- (N = 101) and Afro-Brazilians (N = 70). The PON1*55 and PON1*192 allele frequencies were significantly different in these ethnic groups (p < 0.05 and p < 0.001, respectively). The genotype frequencies for PON1*55 (LL, LM, and MM) in Euro- and Afro-Brazilians were 33, 56, and 11% and 47, 49, and 4%, respectively. The genotype frequencies for PON1*192 were significantly different in Euro- and Afro-Brazilians (QQ, QR, RR: 48, 42, and 10% and 21, 52, and 27%, respectively; p < 0.001). The haplotype frequency distributions were also significantly different in Euro- (LQ = 30.20%; LR = 30.69%; and MQ = 39.11%) and Afro-Brazilians (LQ = 24.97%; LR = 46.46%; MQ = 22.18%; and MR = 6.39%; p < 0.001). Linkage disequilibrium (D) in relation to the maximum expected value was higher in Euro- (100%) than in Afro-Brazilians (58%). We suggest that the high linkage disequilibrium in Caucasians and Asians characterized by the absence or very low frequency of the MR haplotype is mainly due to genetic drift and possibly also to natural selection favoring the PON1*192Q allele or a variant in linkage disequilibrium with it. This seems to be the first study on the PON1 variability at the DNA level in South American samples and one of the few studies on individuals of mixed African origin.

Lipoproteins and hydrolysis of organophosphorus compounds

Paraoxonase of human and animal sera was shown to be a structural part of high density lipoproteins (HDL) by immunoprecipitation, heparin- or polyethyl-eneglycol fractionation, ultracentrifugation and gel chromatography. Frequency distribution of paraoxonase activity in human sera is trimodal. Human individuals, with respect to paraoxon detoxication, can be distinguished into low and high detoxicators using ratios of phenylacetate and paraoxon hydrolysis as well as activation with ethanolamine and sodium chloride. With conversion of α-lipoprotein subtype HDL 3 to HDL 2, specific activities of paraoxonase and arylesterase are increasing about 3.5-fold in low detoxicator individuals and 1.9-fold in high detoxicators, indicating that more than 90% of HDL 2 particle-bound paraoxonase and arylesterase activity are incorporated during the HDL conversion process. HDL cholesterol concentrations in individual sera were shown to be positively correlated to both serum paraoxonase and arylesterase activities.