Ag(I) Pyridine-Amidoxime Complex as the Catalysis Activity Domain for the Rapid Hydrolysis of Organothiophosphate-Based Nerve Agents: Mechanistic Evaluation and Application

Two novel Ag(I) complexes containing synergistic pyridine and amidoxime ligands (Ag-DPAAO and Ag-PAAO) were first designed as complex monomers. Taking advantage of the molecular imprinting technique and solvothermal method, molecular imprinted porous cross-linked polymers (MIPCPs) were developed as a robust platform for the first time to incorporate Ag-PAAO into a polymer material as a recyclable catalyst. Advantageously, the observed pseudo first-order rate constant (k_obs) of MIPCP-Ag-PAAO-20% for ethyl-parathion (EP) hydrolysis is about 1.2 × 10⁴-fold higher than that of self-hydrolysis (30 °C, pH = 9). Furthermore, the reaction mechanism of the MIPCP-containing Ag-PAAO-catalyzed organothiophosphate was analyzed in detail using density functional theory and experimental spectra, indicating that the amidoxime can display dual roles for both the key coordination with the silver ion and nucleophilic attack to weaken the P-OAr bond in the catalytic active site.

Enantioselective Uptake Determines Degradation Selectivity of Chiral Profenofos in Cupriavidus nantongensis X1T

Organophosphorus insecticides account for approximately 28% of the global commercial insecticide market, while 40% of them are chiral enantiomers. Chiral enantiomers differ largely in their toxicities. Enantiomers that are less active or inactive do not offer the needed efficacy but pollute the environment and cause toxicities to non-target species. Cupriavidus nantongensis X1^T, a recently isolated bacterial strain, could degrade S-profenofos 2.3-fold faster than R-profenofos, while the latter is the active enantiomer potently against pest insects and has greater mammalian safety. The degradation enzyme encoded by opdB was expressed via Escherichia coli and purified. The degradation kinetics of R- and S-profenofos showed that both the purified OpdB and crude enzyme extracts had no enantiomer degradation selectivity, which strongly indicated that the degradation selectivity occurred in the uptake process. Metabolite analyses suggested a novel dealkylation pathway. This is the first report of bacterial selective uptake of organophosphates. Selective degradation of S-profenofos over R-profenofos by the strain X1^T suggests a concept of co-application of racemic pesticides and degradation-selective bacteria to minimize contamination and non-target toxicity problems.

Characterization of Dialkyldithiophosphates as Slow Hydrogen Sulfide Releasing Chemicals and Their Effect on the Growth of Maize

Hydrogen sulfide is a key gasotransmitter for plants and has been shown to greatly increase their growth and survival in the presence of environmental stressors. Current methods for slowly releasing hydrogen sulfide use chemicals, such as GYY-4137, but these result in the release of chemicals not found in the environment, and chemicals used may lack structures that can be readily tuned to affect the rate of release of hydrogen sulfide. In this article, we describe the synthesis and slow release of hydrogen sulfide from dialkyldithiophosphates, which are a new set of hydrogen sulfide releasing chemicals that can be used in agriculture. The rates of hydrolysis of dibutyldithiophosphate and GYY-4137 were measured in water at 85 °C and compared with each other to investigate their differences. GYY-4137 is widely used as a chemical that slowly releases H₂S, but its rate of release was not previously quantified. The release of hydrogen sulfide in water at room temperature was measured for a series of dialkyldithiophosphates using a hydrogen sulfide electrode. It was shown that the structure of the dialkyldithiophosphate affected the amount of hydrogen sulfide released. The final degradation products of dibutyldithiophosphate were shown to be phosphoric acid and butanol, which are chemicals found in the environment. This result was notable because it demonstrated that dialkyldithiophosphates degrade to safe, natural chemicals that will not pollute the environment. To demonstrate that dialkyldithiophosphates have potential applications in agriculture, maize was grown for 4.5 weeks after exposure to 1-200 mg of dibutyldithiophosphate, and the weight of corn plants increased by up to 39% at low loadings of dibutyldithiophosphate.

Experimental design of switchable solvent-based liquid phase microextraction for the accurate determination of etrimfos from water and food samples at trace levels by GC-MS

Presented in this study is a simple but efficient switchable polarity solvent microextraction strategy for etrimfos preconcentration from water and food samples for quantification by gas chromatography mass spectrometry. Repeatability of the extraction process and instrumental measurements were enhanced by using deuterated bisphenol A as internal standard. Significant parameters of the extraction method were fitted into an experimental design model to study the effects of parameters on extraction output, as well as mutual effects of combined parameters. The design model was formed with 51 experimented data obtained from the combination of sodium hydroxide volume, switchable solvent volume, and vortex period at three levels. The method was validated by applying optimum conditions attained from the model predictor. The detection limit was found to be 1.3 ng/mL and it corresponded to an enhancement factor of about 54 folds when compared to direct GC-MS measurement. Etrimfos was not detected in the water and food samples tested but the results (92-107%) obtained from spiked recovery experiments established that etrimfos when present in the selected matrices can be accurately and precisely quantified.

Covalent binding of the organophosphate insecticide profenofos to tyrosine on α- and β-tubulin proteins

Organophosphorus (OP) compounds can bind covalently to many types of proteins and form protein adducts. These protein adducts can indicate the exposure to and neurotoxicity of OPs. In the present work, we studied adduction of tubulin with the OP insecticide profenofos in vitro and optimized the method for detection of adducted peptides. Porcine tubulin was incubated with profenofos and was then digested with trypsin, followed by mass spectrometric identification of the profenofos-modified tubulin and binding sites. With solvent-assisted digestion (80% acetonitrile in digestion solution), the protein was digested for peptide identification, especially for some peptides with low mass. The MALDI-TOF-MS and LC-ESI-TOF-MS analysis results showed that profenofos bound covalently to Tyr83 in porcine α-tubulin (TGTY*₈₃R) and to Tyr281 in porcine β-tubulin (GSQQY*₂₈₁R) with a mass increase of 166.02 Da from the original peptide fragments of porcine tubulin proteins. Tyrosine adduct sites were also confirmed by MALDI-TOF/TOF-MS analysis. This result may partially explain the neurotoxicity of profenofos at low doses and prolonged periods of exposure.

Reductive transformation of profenofos with nanoscale Fe/Ni particles

Profenofos is an abundantly used organophosphate pesticide in agriculture but its excessive use may lead to hazardous effects on environment. Thus, the present study focused on the reductive transformation of this pesticide in the presence of Fe/Ni bimetallic nanoparticles by optimizing the process parameters such as stirring time, nanoparticles dose, pH, and initial pesticide concentration. The results of reductive transformation were compared with photodegradation studies. It was found that with the increase in UV irradiation time, the percent degradation was increased. After 660 min, a 78% photodegradation of 100 μM solution of pesticide was observed. On increasing the initial pesticide concentration to 200 μM, the maximum degradation was achieved in 570 min, but here, only 73% degradation was observed. The rates of photodegradation observed with 100 to 400 μM solutions were 1.4 × 10^-3, 1.5 × 10^-3, 1.5 × 10^-3, and 5 × 10^-4 min^-1 respectively.In case of reductive transformation carried out in the presence of Fe/Ni bimetallic nanoparticles, the degradation was observed to be increased from 78 to 93.9% in only 180 min. A further increase in pesticide concentration led to a decrease in degradation. Under these conditions, the rate of reaction was found to be 1.09 × 10^-2 min^-1. A 93% degradation of profenofos was further increased to 98% when the quantity of nanoparticles was increased twice; hence, a significant reduction in time of irradiation was observed. Reductive transformation of pesticide thus provided an efficient and cheaper method for reducing the burden of profenofos from the environment.

Enantioselective apoptosis and oxidative damage induced by individual isomers of profenofos in primary hippocampal neurons

The purpose of this study was to investigate the apoptosis-related cytotoxic effects and molecular mechanisms of individual isomers of profenofos (PFF) on primary hippocampal neurons at 1.0 to 20 mg L^-1. The cell viability and lactate dehydrogenase (LDH) efflux indicated that (-)-PFF exposure was associated with more toxic effects than (+)-PFF above the concentration of 5 mg L^-1 (P < 0.5). Flow cytometric results showed that the percentages of apoptotic cells incubated with 20 mg L^-1 (-)-PFF, (+)-PFF and rac-PFF for 24 h reached 23.4%, 9.2% and 14.2% (P < 0.01), respectively. Hippocampal neurons incubated with (-)-PFF, (+)-PFF and rac-PFF exhibited a dose-dependent accumulation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) and a dose-dependent inhibition of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activity, implying that the defense system of the tests induces oxidative damage. A statistically significant difference was observed between the two enantiomers at 5 mg L^-1 and above. Moreover, the results showed that (-)-PFF exposure caused a significant loss in mitochondrial transmembrane potential (MMP), an upregulation of Ca²⁺ and Bax protein expression, a downregulation of Bcl-2 protein expression, and the activation of caspase-3 and caspase-9 in a dose-dependent manner; (+)-PFF and rac-PFF exhibited these effects to a lesser degree. All results suggest that PFF induced apoptosis in rat hippocampal neurons via the mitochondria-mediated pathway, and oxidative stress is one of the factors of PFF-induced apoptosis. In addition, (-)-PFF appears to play an important role in oxidative stress and apoptosis, indicating that enantioselectivity should be considered when assessing ecotoxicological effects and health risks of chiral pesticides.

[EXPERIMENTAL STUDY OF SPECIFIC ACTIVITY OF 1.3-DIAZINON-4 COM- POUND PYaTd1 DERIVATIVE IN VIVO]

AIM

Study anti-leprosy activity of.a 1.3-diazinon-4 compound derivative under the labora- tory code PYaTd1 on the model of intra-plantar infection of mice and evaluate the character of its antibacterial effect.

MATERIALS AND METHODS

Study of specific activity was carried out in vivo on the experimental model of leprosy, proposed by Shepard C.C., that assumes execution of intraplantar infection of mice with a suspension of mycobacteria, produced from lepromas or autopsy tissue of a non-treated leprosy infected, or from tissues of experimental mice, previously infected with Mycobacterium leprae from non-treated patients. The study was carried out on 120 CBA line-mice infected with M.leprae (VIII passage) from patient M; Dapsone and PYaTdl compound were administered to animals next day after the infection with forage at a dose of 25 mg/kg for 4.5, 6, 9 and 11 months. The mice were split into 3 groups: control (infected.without treatment), com- parison (infected, receiving.dapsone), experimental (infected, receiving PYaTdl). After.the control term the mice were euthanized under chloroform anesthesia. Suspensions for quantification of mycobacteria were prepared from paw pads. Smears were stained by Ziehl-Nilsson.

RESULTS

After 4.5 months the intensity of infect reproduction under, the effect of dapsone and PYaTd1 was reduced compared with control by 18 - 25 times. After a 6-mont course - by 50 - 75% and after 9 months - by 85 - 90%. After 11 months in mice that had received PYaTd1, an intensive suppression of microorganism reproduction as observed: the yield in paws was 70 times lower than in control. In the group that had received dapsone, a reduction of the number of mycobacteria by 20 - 25 times was detected, it was significantly less effective than under the conditions of PYaTd1 admnistration.

CONCLUSION

A novel 1.3-diazinon- 4 derivative under the code PYaTd1 can actively supress reproduction of-M. leprae, that gives evidence regarding its specific anti-mycobacterial activity and determines perspectives of its further studies.

Dissipation of deltamethrin, triazophos, and endosulfan in ready mix formulations in tomato (Lycopersicon esculentum L.) and Egg plant (Solanum melongena L.)

Persistence of delltamethrin, endosulfan, and triazophos in egg plant and tomato was studied following application of two ready mix formulations of insecticides viz. deltametrhin and endosulfan (Cobra 5000; 0.75% deltamethrin + 29.5% endosulfan) and deltamethrin and triazophos (Annaconda Plus; 1% deltamethrin + 35% triazophos) at recommended (1.0 L/ha and double dose 2.0 L/ha). The residues of deltamethrin persisted till 7 and 5 days in tomato and egg plant fruits, respectively, in the ready mix formulation of Cobra 5000 whereas endosulfan persisted till 15 and 10 days in tomato and egg plant fruits, respectively. Dissipation of the insecticides followed first-order kinetics with half-life values of deltamethrin and endosulfan ranged from 2.6 to 4.7 and 1.4 to 1.7 days, respectively, for both the vegetables. In case of combination mix of deltamethrin and triazophos (Annaconda Plus), deltamethrin persisted beyond 5 days in both tomato and egg plant fruits, while triazophos persisted till 10 days in both the vegetables. Residues of deltamethrin and triazophos dissipated with half-life of 2.6-4.2 and 1.7-4.1 days, respectively, on tomato and egg plant fruits. Based on the Codex MRL limits, a safe waiting period of 5 and 3 days is suggested for tomato and egg plant, respectively, for the ready mix formulation of deltamethrin and endosulfan (Cobra 5000), and 5-day waiting period is suggested for tomato and egg plant for the combination mix of deltamethrin and triazophos.

Combined treatment technology based on synergism between hydrodynamic cavitation and advanced oxidation processes

The present work highlights the novel approach of combination of hydrodynamic cavitation and advanced oxidation processes for wastewater treatment. The initial part of the work concentrates on the critical analysis of the literature related to the combined approaches based on hydrodynamic cavitation followed by a case study of triazophos degradation using different approaches. The analysis of different combinations based on hydrodynamic cavitation with the Fenton chemistry, advanced Fenton chemistry, ozonation, photocatalytic oxidation, and use of hydrogen peroxide has been highlighted with recommendations for important design parameters. Subsequently degradation of triazophos pesticide in aqueous solution (20 ppm solution of commercially available triazophos pesticide) has been investigated using hydrodynamic cavitation and ozonation operated individually and in combination for the first time. Effect of different operating parameters like inlet pressure (1-8 bar) and initial pH (2.5-8) have been investigated initially. The effect of addition of Fenton's reagent at different loadings on the extent of degradation has also been investigated. The combined method of hydrodynamic cavitation and ozone has been studied using two approaches of injecting ozone in the solution tank and at the orifice (at the flow rate of 0.576 g/h and 1.95 g/h). About 50% degradation of triazophos was achieved by hydrodynamic cavitation alone under optimized operating parameters. About 80% degradation of triazophos was achieved by combination of hydrodynamic cavitation and Fenton's reagent whereas complete degradation was achieved using combination of hydrodynamic cavitation and ozonation. TOC removal of 96% was also obtained for the combination of ozone and hydrodynamic cavitation making it the best treatment strategy for removal of triazophos.

Understanding thio-effects in simple phosphoryl systems: role of solvent effects and nucleophile charge

Recent experimental work (J. Org. Chem., 2012, 77, 5829) demonstrated pronounced differences in measured thio-effects for the hydrolysis of (thio)phosphodichloridates by water and hydroxide nucleophiles. In the present work, we have performed detailed quantum chemical calculations of these reactions, with the aim of rationalizing the molecular bases for this discrimination. The calculations highlight the interplay between nucleophile charge and transition state solvation in SN2(P) mechanisms as the basis of these differences, rather than a change in mechanism.

Mechanism behind Resistance against the Organophosphate Azamethiphos in Salmon Lice (Lepeophtheirus salmonis)

Acetylcholinesterase (AChE) is the primary target for organophosphates (OP). Several mutations have been reported in AChE to be associated with the reduced sensitivity against OP in various arthropods. However, to the best of our knowledge, no such reports are available for Lepeophtheirus salmonis. Hence, in the present study, we aimed to determine the association of AChE(s) gene(s) with resistance against OP. We screened the AChE genes (L. salmonis ace1a and ace1b) in two salmon lice populations: one sensitive (n=5) and the other resistant (n=5) for azamethiphos, a commonly used OP in salmon farming. The screening led to the identification of a missense mutation Phe362Tyr in L. salmonis ace1a, (corresponding to Phe331 in Torpedo californica AChE) in all the samples of the resistant population. We confirmed the potential role of the mutation, with reduced sensitivity against azamethiphos in L. salmonis, by screening for Phe362Tyr in 2 sensitive and 5 resistant strains. The significantly higher frequency of the mutant allele (362Tyr) in the resistant strains clearly indicated the possible association of Phe362Tyr mutation in L. salmonis ace1a with resistance towards azamethiphos. The 3D modelling, short term survival experiments and enzymatic assays further supported the imperative role of Phe362Tyr in reduced sensitivity of L. salmonis for azamethiphos. Based on all these observations, the present study, for the first time, presents the mechanism of resistance in L. salmonis against azamethiphos. In addition, we developed a rapid diagnostic tool for the high throughput screening of Phe362Tyr mutation using High Resolution Melt analysis.

Ab initio/DFT calculations of butyl ammonium salt of O,O'-dibornyl dithiophosphate

O,O'-dibornyl dithiophosphete has been synthesized by the reaction of P2S5 and borneol in toluene. Fourier Transform Infrared spectra (FT-IR) of the title compound are measured. The molecular geometry, vibrational frequencies, infrared intensities and NMR spectrum of the title compound in the ground state have been calculated by using the density functional theory (DFT) and ab initio Hartree-Fock (HF) methods with the basis set of 6-31G(d). The computed bond lengths and bond angles show the good agreement with the experimental data. Moreover, the vibrational frequencies are calculated and the scaled values have been compared with experimental FT-IR spectra. Assignments of the vibrational modes are made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. The observed and calculated FT-IR and NMR spectra are in good agreement with each other.

Degradation of VX surrogate profenofos on surfaces via in situ photo-oxidation

Surface degradation of profenofos (PF), a VX nerve gas surrogate, was investigated using in situ photo-oxidation that combines simple instrumentation and ambient gases (O2 and H2O) as a function of exposure conditions ([O3], [OH], UV light λ = 185 and/or 254 nm, relative humidity) and PF film surface density (0.38-3.8 g m(-2)). PF film 0.38 g m(-2) fully degraded after 60 min of exposure to both 254 and 185 nm UV light in humidified air and high ozone. The observed pseudo-first-order surface reaction rate constant (kobs = 0.075 ± 0.004 min(-1)) and calculated hydroxyl concentration near the film surface ([OH]g = (9 ± 2) × 10(7) molecules cm(-3)) were used to determine the second-order rate constant for heterogeneous reaction of PF and OH (k(OH)PF = (5 ± 1) × 10(-12) cm(3) molec(-1) s(-1)). PF degradation in the absence of 185 nm light or without humidity was lower (70% or 90% degradation, respectively). With denser PF films ranging from 2.3 to 3.8 g m(-2), only 80% degradation was achieved until the PF droplet was redissolved in acetonitrile which allowed >95% PF degradation. Surface product analysis indicated limited formation of the nontoxic phosphoric acid ester but the formation of nonvolatile chemicals with increased hydrophilicity and addition of OH.

Biodegradation of profenofos by Bacillus subtilis isolated from grapevines (Vitis vinifera)

The biodegradation of profenofos, an organophosphorus insecticide, by four Bacillus subtilis strains, namely, DR-39, CS-126, TL-171, and TS-204, isolated from grapevines or grape rhizosphere was studied in liquid culture, on grape berries, and in vineyard soil. Each of the four B. subtilis strains enhanced the degradation of profenofos in all three matrices. Degradation rate constants were best obtained by first + first-order kinetics module. In nutrient broth spiked with 5 μg/mL profenofos, inoculation with B. subtilis strains DR-39, CS-126, TL-171, and TS-204 reduced the half-life (DT50) of profenofos to 4.03, 3.57, 2.87, and 2.53 days, respectively, from the DT50 = 12.90 days observed in the uninoculated control. In Thompson Seedless grapes sprayed with profenofos at a field dose of 1250 mL ai/ha, the DT50 values were 1.07, 1.00, 2.13, and 2.20 days in grapes inoculated with B. subtilis strains DR-39, CS-126, TL-171, and TS-204, respectively, as compared to 2.20 days in uninoculated grapes. These four B. subtilis strains also enhanced the degradation of profenofos in autoclaved soil (DT50 = 5.93, 7.47, 6.00, and 4.37 days) and in nonautoclaved soil (DT50 = 0.87, 2.00, 2.07, and 2.43 days) amended with 5 μg/g profenofos from the half-lives of 17.37 and 14.37 days in respective uninoculated soils. Growth dynamic studies indicated that all four B. subtilis strains were able to establish and proliferate on berries and soil equally well in the presence or absence of profenofos. Degradation product 4-bromo-2-chlorophenol was identified by GC-MS. Strain DR-39 was most effective in the natural environments of grape and soil.

Stabilization treatment of the heavy metals in fly ash from municipal solid waste incineration using diisopropyl dithiophosphate potassium

A stabilization treatment was developed for heavy metals in fly ash from municipal solid waste incineration using the heavy metal chelator diisopropyl dithiophosphate potassium (DDP). The mechanism and effect of the DDP chelator treatment on heavy metals in the fly ash was also studied, along with the form transformation rules of the heavy metals after DDP chelator treatment. The results show that 1% DDP achieves a stabilization rate of over 95% for Pb, Zn, and Cd. The effect of DDP was better than that of inorganic stabilizers such as sodium sulphide and lime. The heavy metal concentrations in the leachate after the treatment were lower than those required by the Pollution Control Standards for Hazardous Waste Landfill (GB18598-2001). At pH 1-13, the heavy metal concentrations in the fly ash leachate were far lower than those using the inorganic stabilizers sodium sulphide and lime. DDP retains its stabilizing effect under a broader pH range. After stabilization treatment, the heavy metals in the exchangeable fraction and those bound to carbonates were mainly transformed into those bound to organic matter. This process decreases the unstable content and reduces the risk of secondary pollution of the stabilized products in the environment.

Destruction of halogen-containing pesticides by means of detonation combustion

Pesticides that contain a halogen functional group have been destructed by means of detonative combustion. The following compounds were examined: (1) atrazine-2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine-herbicide; (2) bromophos-O,4-bromo-2,5-dichlorophenyl O,O-dimethyl phosphorothioate-insecticide; (3) chloridazon-5-amino-4-chloro-2-phenylopyridazin-3(2H)-one-herbicide; (4) linuron-3-(3,4-dichlorophenyl)-1-metoxy-1-methylurea-herbicide; (5) metoxychlor-1,1,1-trichloro-2,2-bis(4-metoxyphenyl)ethane-insecticide and acaricide; and (6) trichlorfon-dimethyl 2,2,2-trichloro-1-hydroxyethylphosphonate-insecticide. Explosive material has been produced on the basis of ammonium nitrate, which served as an oxidizer while the pesticides were used as fuels. Composition of the explosive was adjusted in such a way as to respect thermodynamic parameters. Detonative decomposition of the mixtures has been carried out in shot-holes pre-drilled in soil. Efficiency of the pesticide decomposition has been examined with gas chromatography in order to determine pesticides residues in the environment. It was found that for some, the amount of pesticides in some compounds in the analyzed samples after decomposition was below the determination threshold of the applied method.

Enantiomeric separation and toxicity of an organophosporus insecticide, pyraclofos

Despite the fact that the biological processes of chiral pesticides are enantioselective, knowledge of the toxicities of pyraclofos due to enantiospecificity is scarce. In this study, the optical isomers of pyraclofos were separated and their toxicities to butyrylcholinesterase (BChE) and Daphnia magna were assessed. Baseline resolution of the enantiomers was obtained on both Chiralcel OD and Chiralpak AD columns. The effect of the mobile phase composition and column temperature were then discussed. The resolved enantiomers were characterized by their optical rotation and circular dichroism signs. The anti-BChE tests demonstrated that (-)-pyraclofos was about 15 times more potent than its (+)-form. However, acute aquatic assays suggested that (+)-pyraclofos was about 6 times more toxic than its antipode. Moreover, the joint toxicity of pyraclofos enantiomers to D. magna was found to be an additive effect. These results demonstrated that the overall toxicity of pyraclofos should be assessed using the individual enantiomers.

Different enantioselective degradation of pyraclofos in soils

This study investigated the enantioselective degradation behavior of pyraclofos in three soils (NC, HZ, and ZZ) under native and sterilized conditions. The absolute configuration of pyraclofos enantiomers has been determined by the combination of experimental and calculated electronic circular dichroism spectra. S-(+)- and R-(-)-Pyraclofos were separated and determined on a cellulose tri-(4-chloro-3-methylphenylcarbamate) (Lux Cellulose-4) chiral column by reversed-phase high-performance liquid chromatography-tandem mass spectrometry. Pyraclofos enantiomers were configurationally stable in three soils and no interconversion was observed during the incubation of enantiopure S-(+)- or R-(-)-pyraclofos under native conditions. The enantioselective degradation behavior of chiral pyraclofos was dramatically different in three soils under native conditions, with half-lives (t(1/2)) of pyraclofos in NC, HZ, and ZZ soils of 2.6, 13.4, and 7.8 days for S-(+)-pyraclofos and 9.2, 9.3, and 8.2 days for R-(-)-pyraclofos. Compared to the half-lives (t(1/2)) of rac-pyraclofos of 21.5, 55.9, and 14.4 days in sterilized NC, HZ and ZZ soils, the degradation velocity was greatly improved in native soils, indicating that degradation was greatly attributed to microbially mediated processes in agricultural cultivating soils.

Adsorption and degradation of triazophos, chlorpyrifos and their main hydrolytic metabolites in paddy soil from Chaohu Lake, China

Triazophos and chlorpyrifos are organophosphorus pesticides (OPs), and their primary hydrolytic metabolites are 1-phenyl-3-hydroxy-1,2,4-triazole (BZC) and 3,5,6-trichloro-2-pyridinol (TCP). In this study, the adsorption and degradation of triazophos, chlorpyrifos, BZC and TCP were investigated in paddy soil from Chaohu Lake, China. Adsorption tests demonstrated that the adsorption of these compounds to soils could be described by the Freundlich equation. Moreover, chlorpyrifos displayed the highest affinity for adsorption, followed by triazophos, BZC and TCP. Degradation of these compounds in non-sterile soil followed first-order exponential decay kinetics, and the half-life (t(1/2)) of these contaminants ranged from 8.40 to 44.34 d. Sterilization of soil decreased the degradation rate, indicating that microorganisms played a significant role in the degradation of these compounds. The values of t(1/2) and K(oc) were fitted to obtain models that could predict the leaching potential of the contaminants from soil. Compared to their parent compounds, BZC and TCP showed high potential for leaching into groundwater. The inoculation of OPs-degrading bacterium (Diaphorobacter sp. GS-1) removed 95.38%, 100% and 100% of triazophos, chlorpyrifos and BZC in paddy soil after 21 d, respectively. The pollution risk of triazophos, chlorpyrifos and BZC could be greatly decreased by inoculating soil with Diaphorobacter sp. GS-1, which decreases the t(1/2) of the contaminants.

Dissipation of cypermethrin, chlorpyriphos, and profenofos in tomato fruits and soil following application of pre-mix formulations

Persistence of cypermethrin, chlorpyriphos, and profenofos in tomato and soil were studied following application of two pre-mix formulations of insecticides viz. Roket 44EC (profenofos 40% + cypermethrin 5%) and Action-505EC (chlorpyriphos 50% + cypermethrin 5%) at recommended (0.8-1.0 L ha(-1)) and double dosage (1.6-2.0 L ha(-1)). In all the treatments residues persisted beyond 7 days in tomato fruits. Half-life values were calculated from first-order dissipation kinetics. In the case of Roket 44EC, residues of cypermethrin on fruits dissipated with half-life of 2.0-3.6 days, whereas residues of profenophos dissipated with the half-life of 2.2-5.4 days. In the case of Action-505EC, residues of chlorpyriphos and cypermethrin dissipated from fruits with the half-life values of 2.9-3.3 and 2.5-4.8 days, respectively. In soil, residues of profenofos persisted for 7-15 days, whereas residues of chlorpyrophos and cypermethrin persisted for 0-7 days only.

Chelation of heavy metals by potassium butyl dithiophosphate

Potassium butyl dithiophosphate (PBD) was developed and introduced as a new chelating agent for heavy metal removal. The synthesized PBD were characterized by IR and NMR. The effects of pH, chelating agent dosage, and other heavy metal ions on the performance of PBD in Cd2+ removal from water are investigated. Experimental results showed that the chelating agent could be used to treat acidic heavy metal wastewater. The Cd2+ removal was not affected by solution pH value within the range of 2 to 6. The Cd2+ removal rate could reach over 99%. Therefore, the deficiency of the precipitation process using hydroxide under alkaline condition can be overcome. Without the need for pH adjustment, the method could save on costs. If Cd2+ co-exists with Pb2+ and Cu2+, the affinity of the chelating agent with these three heavy metal ions was in the order of: Cu2+ > Pb2+ > Cd2+. Through PBD chelating precipitation, all the contents of Pb2+, Cd2+, and Cu2+ in wastewater met the standard levels through a one-step treatment. The one-step treatment process was superior to the process (sectional treatment is required) of precipitation with hydroxide. When the pH was between 3 and 11, the amount of leached chelated Cd2+ was much lower than that obtained by precipitation with hydroxide. Therefore, the risk of environmental pollution could be further reduced.

[Thermodynamics adsorption and its influencing factors of chlorpyrifos and triazophos on the bentonite and humus]

The adsorption of chlorpyrifos and triazophos on bentonite and humus was investigated by using the equilibrium oscillometry. The adsorption capacity of chlorpyrifos and triazophos on humus was great higher than bentonite at the same concentration. Equilibrium data of Langmuir, Freundlich isotherms showed significant relationship to the adsorption of chlorpyrifos and triazophos on humus (chlorpyrifos: R2 0.996 4, 0.996 3; triazophos: R2 0.998 9, 0.992 4). Langmuir isotherm was the best for chlorpyrifos and triazophos on bentonite (chlorpyrifos: R2 = 0.995 7, triazophos: R2 = 0.998 9). The pH value, adsorption equilibrium time and temperature were the main factors affecting adsorption of chlorpyrifos and triazophos on bentonite and humus. The adsorption equilibrium time on mixed adsorbent was 12h for chlorpyrifos and 6h for triazophos respectively. The mass ratio of humus and bentonite was 12% and 14% respectively, the adsorption of chlorpyrifos and triazophos was the stronglest and tended to saturation. At different temperatures by calculating the thermodynamic parameters deltaG, deltaH and deltaS, confirmed that the adsorption reaction was a spontaneous exothermic process theoretically. The adsorption was the best when the pH value was 6.0 and the temperature was 15 degrees C.

Microbial community variation in phytoremediation of triazophos by Canna indica Linn. in a hydroponic system

Phytoremediation of triazophos (O,O-diethyl-O-(1-phenyl-1,2,4-triazole-3-base) sulfur phosphate, TAP) pollution by Canna indica Lim. in a hydroponic system has been well studied, whereas the microbial mechanism on TAP degradation is still unknown. The variation in microbial community compositions was investigated by analyzing phospholipid fatty acids (PLFAs) profiles in microbes under TAP exposure. The TAP exposure resulted in an increase in proportions of fatty acid 16:0 and decrease in fatty acid 18:2omega9,12c, indicating that TAP may stimulate the reproduction of microorganisms and inhibit the growth of fungi to some degree. Significant correlation was found between the ratio of fungi to bacteria and TAP removal (r2 = 0.840, p < 0.01). In addition, the microbial community in the phytoremediation system with C. indica was dominated by Gram negative bacteria, which possibly contributed to the degradation of TAP. These results indicated that TAP might induce the colonization of bacteria in the hydroponic system planted with C. indica, and lead to a discrimination of microbial community, which might be one of the mechanisms on TAP dissipation in phytoremediation system.

Removal of triazophos pesticide from wastewater with Fenton reagent

The catalytic oxidation of triazophos pesticide from wastewater using Fenton reagent was investigated at bench-scale in this study. Synthesized wastewater and actual industrial triazophos pesticide wastewater taken from a pesticide company were examined sequentially. The COD values of the synthesized and actual industrial triazophos pesticide wastewater samples were 3242 and 3418 mg/L, respectively, and the triazophos concentration in these wastewater samples was 0.06% by weight. The effects of reaction conditions including the dosages of FeSO(4).7H(2)O and H(2)O(2), the pH value of the environment, and the stirring time on COD removal from the synthesized wastewater were evaluated, and COD removal efficiency of 96.3% with a corresponding effluent COD value of 120 mg/L was achieved under optimal reaction conditions of a pH value of 4, a dosage of 2.5 g/L of FeSO(4).7H(2)O and 100 mL/L of 30% H(2)O(2) solution, and a stirring time of 90 min. Results also showed that 71.2% of nitrogen and 68.5% of phosphorous in the synthesized triazophos wastewater were converted to NO(3)(-) and PO(4)(3-), respectively, at the optimal reaction condition. When the actual industrial wastewater was treated at a pH value of 4, COD removal efficiency of 85.4% with a corresponding effluent COD value of 499 mg/L were reached at optimal condition of a dosage of 5.0 g/L of FeSO(4).7H(2)O and 75 mL/L of 30% H(2)O(2) solution, and a stirring time of 90 min. The results of this study can be referred for the design of a treatment process for the actual industrial triazophos wastewater.

Synthesis, crystal structure, insecticidal activity and DFT study on the geometry and vibration of O-(E)-1-{1-[(6-chloropyridin-3-yl)methyl]-5-methyl-1H-1,2,3-triazol-4-yl}ethyleneamino-O-ethyl-O-phenylphosphorothioate

The title compound, O-(E)-1-{1-[(6-chloropyridin-3-yl)methyl]-5-methyl-1H-1,2,3-triazol-4-yl}ethyleneamino-O-ethyl-O-phenylphosphorothioate, has been synthesized via the condensation reaction of 1-{1-[(6-chloropyridin-3-yl)methyl]-5-methyl-1H-1,2,3-triazol-4-yl}ethanone oxime and O-ethyl-O-phenylphosphorochloridothioate in the presence of NaOH powder in refluxing EtOH. Its structure was characterized by (1)H NMR, FTIR, Raman, elemental analysis and X-ray single crystal diffraction. The results of preliminary bioassays indicated that the title compound displays good insecticidal activity. Density functional (DFT) calculations have been carried out for the title compound by using the Becke-Lee-Yang-Parr's three-parameter hybrid functional (B3LYP) method at 6-31G and 6-31G basis sets. The calculated results show that the predicted geometry can well reproduce the structural parameters. The vibrational wave numbers of the title compound were calculated at same level. Predicted vibrational frequencies have been assigned and compared with experimental IR and Raman spectra and they are supported each other.

Prediction for the mixture toxicity of six organophosphorus pesticides to the luminescent bacterium Q67

Organophosphorus (OP) pesticides are ubiquitous in the surface water as mixtures. To examine the mixture toxicity in the multi-component space, the uniform design (UD) which can explore the concentration changes with few experimental efforts was employed to design the mixtures. On the other hand, the fixed concentration ratio ray was applied into six UD mixtures and two equivalent-effect concentration mixtures to build the whole concentration-response curves to overcome the demerit of the classical "point-to-point" method. The experimental toxicities of six pesticides and their mixtures to the luminescent bacterium Q67 were determined. The mixture toxicities were predicted by two models, concentration addition (CA) and independent action (IA). The results showed that all the mixture toxicities observed had no significant differences from the ones predicted by CA. However, the mixture toxicities were also well predicted by IA especially at the low-concentration section.

Risk assessment of the organophosphate pesticides isazofos and pyraclofos using a 21-day dietary toxicity study in Japanese quail

Six-week-old male and female Japanese quails (Coturnix japonica) received two organophosphate pesticides, isazofos and pyraclofos, for a 21-day dietary toxicity test, based on the OECD workshop report. During the treatment period, body weight and food consumption of the quail decreased with exposure to either isazofos or pyraclofos. Using the up-and-down procedure to determine the 50% mortality value, we found that the 21-day LC(50) of isazofos and pyraclofos were 40 and 87 mg/kg body weight, respectively. Ataxia, salivation, diarrhea, ruffled feathers, and convulsions at a dead point were observed with both pesticides. The tips of the villi were necrotic in the high dosage groups of isazofos- and pyraclofos-treated quail. Based on these results, body weight, food consumption, clinical signs, and histopathological findings may be useful parameters for detecting the dietary toxicity associated with isazofos and pyraclofos exposure. In addition, Japanese quail could be an excellent bird model for monitoring the toxicological risks of pesticides in Korea.

Roles of neuropeptides in O,O,S-trimethylphosphorothioate (OOS-TMP)-induced anorexia in mice

O,O,S-Trimethylphosphorothioate (OOS-TMP), an impurity present in various organophosphorus insecticides, has previously been shown to induce hypophagia. The major goal of this study was to investigate its mechanism of action. Both intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) injection transiently induced hypophagia at a dose of 5mg/kg within 6h, without causing lung injury. Hypophagia was accompanied by up-regulation of corticotropin releasing factor (CRF) (2.92+/-0.45 vs. 1.7+/-0.5, at 2h after i.c.v., 3.40+/-1.38 vs. 1.76+/-0.41 at 6h after i.p., P<0.05) in the hypothalamus. After i.c.v. injection, hypophagia recovered by 6h after dosing. At doses higher than 5mg/kg, i.c.v. injection induced continuous hypophagia from 20min to 72h after dosing, accompanied by hypothermia and lung injury. OOS-TMP was considered to induce hypophagia through enhancing expression of CRF.

Enantioselective acetylcholinesterase inhibition of the organophosphorous insecticides profenofos, fonofos, and crotoxyphos

A large number of organophosphorous insecticides (OPs) are chiral compounds, and yet enantioselectivity in their environmental fate and effects is rarely addressed. In the present study, we isolated individual enantiomers of three OPs, profenofos, fonofos, and crotoxyphos, and evaluated enantioselectivity in their inhibition of acetylcholinesterase (AChE). Acetylcholinesterase inhibition by the enantiomers and racemates was determined in vivo in the aquatic invertebrate Daphnia magna and in Japanese medaka (Oryzias latipes) as well as in vitro with electric eel (Electrophorus electricus) and human recombinant AChEs. The overall results showed variable sensitivity between AChE enzymes from different species as well as variable magnitude of enantioselectivity in enzyme inhibition. The (-)-enantiomer of profenofos was 4.3- to 8.5-fold more inhibitory to AChE in vivo, whereas (-)-fonofos was 2.3- to 29-fold more potent than the corresponding (+)-enantiomer. The (+)-enantiomer of crotoxyphos was 1.1- to 11-fold more inhibitory to AChE than the (-)-enantiomer. In contrast, the in vitro results showed (+)-profenofos to be 2.6- to 71.8-fold more inhibitory than the (-)-enantiomer and (-)-crotoxyphos to be 1.6- to 1.9-fold more active than the (+)-enantiomer. The reversed direction of enantioselectivity observed between the in vivo and in vitro assays suggests enantioselectivity within toxicodynamic processes such as uptake, biotransformation, or elimination. Findings from the present study provide evidence of enantioselectivity in the AChE inhibition of chiral OPs in nontarget organisms and indicate the need to consider enantiomers individually when assessing environmental risk of these chiral pesticides.

Photocatalytic degradation of triazophos in aqueous titanium dioxide suspension: identification of intermediates and degradation pathways

The photocatalytic degradation of triazophos in aqueous TiO2 suspension has been studied in a photoreactor operating with simulated solar radiation. The decrease in triazophos concentration followed first-order kinetics with a half-life of 4.76+/-0.42 h at a TiO2 suspension concentration of 10 mg/L. Seventeen degradation products were identified using HPLC-UV, HPLC/MS/MS, GC/MS/MS and IC, and by comparing retention times and spectra with commercially available authentic standards. On the basis of the observed transformation products, two routes were proposed, one based on the initial oxidative cleavage of PS bond to PO bond, and the other on initial cleavage of the ester P-O bonds. Photocatalysis holds promise for the solar treatment of pesticide-contaminated waters.

A semisynthetic epitope for kinase substrates

The ubiquitous nature of protein phosphorylation makes it challenging to map kinase-substrate relationships, which is a necessary step toward defining signaling network architecture. To trace the activity of individual kinases, we developed a semisynthetic reaction scheme, which results in the affinity tagging of substrates of the kinase in question. First, a kinase, engineered to use a bio-orthogonal ATPgammaS analog, catalyzes thiophosphorylation of its direct substrates. Second, alkylation of thiophosphorylated serine, threonine or tyrosine residues creates an epitope for thiophosphate ester-specific antibodies. We demonstrated the generality of semisynthetic epitope construction with 13 diverse kinases: JNK1, p38alpha MAPK, Erk1, Erk2, Akt1, PKCdelta, PKCepsilon, Cdk1/cyclinB, CK1, Cdc5, GSK3beta, Src and Abl. Application of this approach, in cells isolated from a mouse that expressed endogenous levels of an analog-specific (AS) kinase (Erk2), allowed purification of a direct Erk2 substrate.

Solid-phase synthesis of thermolytic DNA oligonucleotides functionalized with a single 4-hydroxy-1-butyl or 4-phosphato-/thiophosphato-1-butyl thiophosphate protecting group

Several thermolytic CpG-containing DNA oligonucleotides analogous to 1 have been synthesized to serve as potential immunotherapeutic oligonucleotide prodrug formulations for the treatment of infectious diseases in animal models. Specifically, the CpG motif (GACGTT) of each DNA oligonucleotide has been functionalized with either the thermolabile 4-hydroxy-1-butyl or the 4-phosphato-/thiophosphato-1-butyl thiophosphate protecting group. This functionalization was achieved through incorporation of activated deoxyribonucleoside phosphoramidite 8b into the oligonucleotide chain during solid-phase synthesis and, optionally, through subsequent phosphorylation effected by phosphoramidite 9. Complete conversion of CpG ODNs hbu1555, psb1555, and pob1555 to CpG ODN 1555 (homologous to 2) occurred under elevated temperature conditions, thereby validating the function of these diastereomeric oligonucleotides as prodrugs in vitro. Noteworthy is the significant increase in solubility of CpG ODN psb1555 and CpG pob1555 in water when compared to that of neutral CpG ODN fma1555 (homologous to 1).

S,S,S-Tris(2-ethylhexyl) phosphorotrithioate as an effective solvent mediator for a mexiletine-sensitive membrane electrode

S,S,S-tris(2-ethylhexyl) phosphorotrithioate proved to be an effective solvent mediator for constructing a mexiletine-sensitive membrane electrode in combination with an ion-exchanger, sodium tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate. Among a series of phosphorus compounds containing phosphoryl (P=O) groups, this solvent mediator showed the highest sensitivity to mexiletine in phosphate-buffered physiological saline containing 0.15 mol L-1 NaCl and 0.01 mol L-1 NaH2PO4/Na2HPO4 (pH 7.4), giving a detection limit of 2x10(-6) mol L-1 with a slope of 58.8 mV decade-1. This is the best reported detection limit of any mexiletine-sensitive electrode developed to date. Owing to its high selectivity toward inorganic cations, the electrode was used to determine the level of mexiletine in saliva, the monitoring of which is quite effective for controlling the dose of this drug noninvasively. The mexiletine concentrations determined with the mexiletine-sensitive electrode compared favorably with those determined by high-performance liquid chromatography.

Products of the Gas-Phase Reactions of OH Radicals with (C2H5O)2P(S)CH3 and (C2H5O)3PS

Products of the gas-phase reactions of OH radicals with O,O-diethyl methylphosphonothioate [(C2H5O)2P(S)CH3, DEMPT] and O,O,O-triethyl phosphorothioate [(C2H5O)3PS, TEPT] have been investigated at room temperature and atmospheric pressure of air using in situ atmospheric pressure ionization mass spectrometry (API-MS) and, for the TEPT reaction, gas chromatography and in situ Fourier transform infrared (FT-IR) spectroscopy. Combined with products quantified previously by gas chromatography, the products observed were: from the DEMPT reaction, (C2H5O)2P(O)CH3 (21+/-4% yield) and C2H5OP(S)(CH3)OH or C2H5OP(O)(CH3)SH (presumed to be C2H5OP(O)(CH3)SH by analogy with the TEPT reaction); and from the TEPT reaction, (C2H5O)3PO (54-62% yield), SO2 (67+/-10% yield), CH3CHO (22-40% yield) and, tentatively, (C2H5O)2P(O)SH. The FT-IR analyses showed that the formation yields of HCHO, CO, CO2, peroxyacetyl nitrate [CH3C(O)OONO2], organic nitrates, and acetates from the TEPT reaction were <5%, 3+/-1%, <7%, <2%, 5+/-3%, and 3+/-2%, respectively. Possible reaction mechanisms are discussed.

Reaction of thiometon and disulfoton with reduced sulfur species in simulated natural environment

The reactions of thiometon and its ethyl analogue, disulfoton, with reduced sulfur species [e.g., bisulfide (HS-), polysulfide (S(n)2-), thiophenolate (PhS-), and thiosulfate (S2O3(2-))] were examined in well-defined aqueous solutions under anoxic conditions. The role of reduced sulfur species was investigated in the abiotic degradation of thiometon and disulfoton. Experiments at 25 degrees C demonstrated that HS-, S(n)2-, PhS-, and S2O3(2-) promoted the degradation of thiometon to a great extent while only S(n)2- and PhS- showed a small accelerating effect in the degradation of disulfoton. Reactions were monitored at varying concentrations of reduced sulfur species to obtain the second-order rate constants. The reactivity of the reduced sulfur species decreased in the following order: S(n)2- > PhS- > HS- approximately S2O3(2-). Transformation products were confirmed by standards or characterized by gas chromatography mass spectrometry. The results illustrate that multiple pathways occur in the reactions with reduced sulfur species, among which the nucleophilic attack at the alpha-carbon of the alkoxy group was the predominant pathway. Activation parameters of the reaction of thiometon and disulfoton with HS- were also determined from the measured second-order rate constants over a temperature range. DeltaH( not equal) values indicated that the reactivity of thiometon toward HS- was much greater than for disulfoton. Nucleophilic attack at the alkoxy group was more important for thiometon than disulfoton. When the measured second-order rate constants at 25 degrees C are multiplied by [HS-] and Sigma[S(n)2-] reported in saltmarsh porewaters, predicted half-lives show that reduced sulfur species present at environmentally relevant concentrations may present an important sink for thiometon in coastal marine environments.

Hapten synthesis for enzyme-linked immunoassay of the insecticide triazophos

Two haptens of the insecticide triazophos (O,O-diethyl O-[1-phenyl-1H-1,2,4-triazol-3-yl] phosphorothioate) were synthesized by introducing appropriate spacers in the O-ethyl site of the analyte molecular structure. First, thiophosphoryl chloride (PSCl(3)) reacts with methanol at low temperature to give O-ethyl dichlorothiophosphate. After reacting with 1-phenyl-3H-1,2,4-triazol, the O-ethyl dichlorothiophosphate was transformed into the intermediate O-ethyl O-(1-phenyl-1H-1,2,4-triazol-3-yl) chlorothiophosphate. Then the intermediate reacts with 4-aminobutyric acid and 6-aminobutyric acid to produce hapten I and hapten II, respectively. The molecule structures of the two haptens were identified by (1)H nuclear magnetic resonance spectrum and mass spectrum. An enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibody was also developed to evaluate the two haptens. Results showed that the monoclonal antibodies with high titers were obtained after immunizing with protein conjugates of these haptens and that the immunoassay has high affinity and specificity to triazophos. These results suggested that the haptens were synthesized successfully and could be used for immunoassay for the rapid screening and sensitive determination of this insecticide.

Single-based resolution for oligodeoxynucleotides and their phosphorothioate modifications by replaceable capillary gel electrophoresis

A replaceable capillary gel electrophoretic (replaceable CGE) method was developed for the separation of two sets of model compounds of single-stranded oligodeoxynucleotide mixtures (18-20 mers), phosphodiester oligodeoxynucleotides (PO-ODNs) and their phosphorothioate modifications (PS-ODNs), with equal sequences differing in a single base. Polyethylene glycol (PEG) 35000 was chosen as the sieving matrix. It was confirmed that PEG polymer solution less influenced resolutions of the PS-ODNs compared with those of the PO-ODNs, while acetonitrile used as an additive in the system improved the separation significantly. It was also noticed that the effect of temperature on separation was much larger than that of denaturant urea.

Synthesis, characterization, and biological properties of small branched RNA fragments containing chiral (Rp and Sp) 2',5'-phosphorothioate linkages

Synthetic branched RNA fragments were prepared to examine the stereochemical requirements for hydrolysis of RNA lariats by the yeast debranching enzyme (yDBR). Specifically, two branched trinucleoside diphosphates and a tetranucleoside triphosphate containing a 2',5'-linked phosphorothioate linkage of defined stereochemistry, namely Rp-A(2'ps5'G)pC, Sp-A(2'ps5'G)pC and Sp-ApA(2'ps5'G)pC, were prepared via solution-phase methods. Unlike the all-phosphodiester control, A(2'p5'G)pC, the Rp-thioated trimer was not cleaved by yDBR, demonstrating that changing the pro-Rp oxygen at the 2',5' phosphodiester bond averts hydrolysis by the enzyme. In contrast, the Sp branched compounds (trimer and tetramer) were cleaved yDBR, albeit with reduced efficiency relative to the corresponding all-phosphodiester branched compounds. Furthermore, the small branched RNAs (5 nt) were not cleaved as efficiently as a 18-nt bRNA, suggesting that the enzyme appears to have a stronger preference for larger bRNA substrates. The non-hydrolyzable branched RNA fragments prepared during these studies may be promising candidates for the future co-crystallization and X-ray analyses of DBR:bRNA complexes.

Multiple-Element Detection in Aqueous Solution and Seawater by Using an On-line Preconcentration Method for Inductively Coupled Plasma Mass Spectrometry

Inductively coupled plasma-mass spectrometry (ICP-MS) incorporated with an on-line preconcentration system was used to determine trace amounts of ten metals including Ni, Cu, Zn, Rh, Ag, Cd, In, Au, Tl, and Pb in aqueous solutions and seawater. These metals, which formed the complexes, were retained in a sorbent microcolumn, followed by elution with methanol through a desolvation unit, which was capable of removing 83% of methanol. The limits of detection for these elements were determined simultaneously to be in the range from 3 to 20 ng/L.

Mechanism of interactions between Hg(II) and Demeton S: an NMR study

The chemical fate of organophosphorus pesticides (OPs) has been proven to depend strongly on the chemistry of their aquatic environment. In particular, metal ions (and metal oxide surfaces) have been known to play an important role in the hydrolytic fate of OPs. Various postulates regarding the mechanism of metal-ion-promoted hydrolysis of OPs have been made over the years. However, direct spectroscopic evidence to pinpoint the hydrolytic products and the exact interaction between metal ions and organophosphorus pesticides are still lacking. We report herein the first in-situ study of the interaction between an aqueous solution of Hg(II) and Demeton S using 1H- and 31P NMR spectroscopy. It was found that the interactions between Hg(II), a soft Lewis acid, and Demeton S tend to be a strong function of the aqueous speciation of Hg(II), and the bonding between Hg2+ and Demeton S does not involve the central P=O bond but rather Hg2+ bonds with the two sulfur atoms in the Demeton S side chain and subsequently stabilizes the Demeton S molecule, a phenomenon not previously reported for any metal ion-OP systems studied. On the basis of this study, generalizations regarding the nature of metal ion binding even within a given class of OPs (i.e., phosphorodithioates, phosphorothioates, phosphorothiolates, etc.) should be avoided or only made with extreme caution.

Role of water in aging of human butyrylcholinesterase inhibited by echothiophate: the crystal structure suggests two alternative mechanisms of aging

Organophosphorus poisons (OP) bind covalently to the active-site serine of cholinesterases. The inhibited enzyme can usually be reactivated with powerful nucleophiles such as oximes. However, the covalently bound OP can undergo a suicide reaction (termed aging) yielding nonreactivatable enzyme. In human butyrylcholinesterase (hBChE), aging involves the residues His438 and Glu197 that are proximal to the active-site serine (Ser198). The mechanism of aging is known in detail for the nerve gases soman, sarin, and tabun as well as the pesticide metabolite isomalathion. Aging of soman- and sarin-inhibited acetylcholinesterase occurs by C-O bond cleavage, whereas that of tabun- and isomalathion-inhibited acetylcholinesterase occurs by P-N and P-S bond cleavage, respectively. In this work, the crystal structures of hBChE inhibited by the ophthalmic reagents echothiophate (nonaged and aged) and diisopropylfluorophosphate (aged) were solved and refined to 2.1, 2.25, and 2.2 A resolution, respectively. No appreciable shift in the position of the catalytic triad histidine was observed between the aged and nonaged conjugates of hBChE. This absence of shift contrasts with the aged and nonaged crystal structures of Torpedo californica acetylcholinesterase inhibited by the nerve agent VX. The nonaged hBChE structure shows one water molecule interacting with Glu197 and the catalytic triad histidine (His438). Interestingly, this water molecule is ideally positioned to promote aging by two mechanisms: breaking either a C-O bond or a P-O bond. Pesticides and certain stereoisomers of nerve agents are expected to undergo aging by breaking the P-O bond.

Thermospray Flame Furnace-AAS Determination of Copper after On-line Sorbent Preconcentration Using a System Optimized by Experimental Designs

The present paper describes the on-line coupling of a flow-injection system to a new technique, thermospray flame furnace-AAS (TS-FF-AAS), for the preconcentration and determination of copper in water samples. Copper was preconcentrated onto polyurethane foam (PUF) complexed with ammonium O,O-diethyldithiophosphate (DDTP), while elution was performed using 80% (v/v) ethanol. An experimental design for optimizing the copper preconcentration system was established using a full factorial (2(4)) design without replicates for screening and a Doehlert design for optimization, studying four variables: sample pH, ammonium O,O-diethyldithiophosphate (DDTP) concentration, presence of a coil and the sampling flow rate. The results obtained from the full factorial and based on a Pareto chart indicate that only the pH and the DDTP concentration, as well as their interaction, exert influence on the system within a 95% confidence level. The proposed method provided a preconcentration factor of 65 fold, thus notably improving the detectability of TS-FF-AAS. The detection limit was 0.22 microg/dm3 and the precision, expressed as the relative standard deviation (RSD) for eight independent determinations, was 2.7 and 1.1 for copper solutions containing 5 and 30 microg/dm3, respectively. The procedure was successfully applied for copper determination in water samples.

Degradation kinetics and products of triazophos in intertidal sediment

This work presents laboratory studies on the degradation of triazophos in intertidal sediment. The overall degradations were found to follow the first-order decay model. After being incubated for 6 d, the percentage of degradations of triazophos in unsterilized and sterilized sediments were 94.5% and 20.5%, respectively. Between the temperatures of 15 degrees C and 35 degrees C, the observed degradation rate constant (kobsd) enhanced as the incubation temperature increased. Triazophos in sediment degraded faster under aerobic condition than under anaerobic one. The water content of sediment had little influence on the degradation when it was in the range of 50%-100%. The values of kobsd decreased with increasing initial concentration of triazophos in sediment, which could result from the microorganism inhibition by triazophos. Four major degradation products, o, o-diethyl phosphorothioic acid, monoethyl phosphorothioic acid, phosphorothioic acid, and l-phenyl-3-hydroxy-1,2,4-triazole, were tentatively identified as their corresponding trimethylsilyl derivatives with a gas chromato-graphy-mass spectrometer. The possible degradation pathway of triazophos in intertidal sediment was proposed. The results revealed that triazophos in intertidal sediment was relatively unstable and could be easily degraded.

Kinetics and products of photo-Fenton degradation of triazophos

Triazophos is a contaminant of wastewater at manufacturing facilities, and remediative treatment may be needed. While toxicity and persistence limit the effectiveness of biological and physicochemical methods, photo-Fenton processes are promising. UV-Fenton and solar-Fenton processes were applied to degrade triazophos. The optimum parameters were 50 mmol/L H(2)O(2), 0.3 mmol/L FeSO(4), and pH 3.0. The decomposition of triazophos by a photo-Fenton process followed first-order kinemics. At 30 degrees C, the half-life of triazophos in a UV-Fenton process ranged from 9.1 min at 2.0 x 10(5) Lx to 27.3 min at 1.0 x 10(5) Lx. At 35 degrees C and with solar irradiation luminance, it ranged within 1.0 x 10(5) -1.2 x 10(5) Lx; the half-life of triazophos in the solar-Fenton process was 11.2 min. Five major degradation products, O,O-diethyl phosphorothioic acid, monoethyl phosphorothioic acid, phosphorothioic acid, 1-phenyl-3-hydroxy-1,2,4-triazole, and phenylsemicarbazine, were tentatively identified as their corresponding trimethylsilyl derivatives with a gas chromatography-mass spectrometer. The possible degradation pathway of triazophos was proposed. The results indicate the potential use of a solar-Fenton treatment for triazophos-contaminated water.

Hydrolytic products and kinetics of triazophos in buffered and alkaline solutions with different values of pH

The hydrolysis of triazophos was studied in buffered solutions in the range of pH 4-10 and in sodium hydroxide solutions with pH values up to 12. The results showed that the degradation of triazophos in the above solutions followed simple pseudo-first-order kinetics. At 35 degrees C, the rate constants in buffered solutions ranged from 0.0222 d(-1) at pH 4 to 0.5357 d(-1) at pH 10, and increased to 0.6251 h(-1) in 0.01 mol/L sodium hydroxide solution. The results also indicated that the base-catalysis was more important than acid-catalysis in the hydrolysis of triazophos. On the basis of the Arrhenius plot, the calculated activation energy (E(a)) and the frequency factor (A) for the hydrolysis of triazophos in buffered solution of pH 10 were 78.6 kJ/mol and 1.13 x 10(13) d(-1), respectively. Hydrolytic products of triazophos in buffered solutions of pH 4 and 10, as well as in sodium hydroxide solution of pH 11, were identified as their corresponding trimethylsilyl derivatives with a gas chromatography-mass spectrometer (GC-MS). The possible hydrolytic pathways of triazophos were also proposed.

Phosphonyl, phosphonothioyl, phosphonodithioyl, and phosphonotrithioyl radicals: generation and study of their addition onto alkenes

The treatment of benzyl dialkyl phosphites and dithiophosphites with benzeneselanyl chloride generates an Arbuzov-type transformation leading to the dialkyl selenophosphates 19a and 19b and to selenophosphorodithioates 21a and 21b. Interaction of these substrates with Lawesson's reagent yields the corresponding selenophosphorothioates 20a and 20b and the selenophosphorotrithioates 22a and 22b. When treated with a radical initiator in the presence of a hydrogen donor and an alkene, all eight phosphorus(V) precursors undergo homolytic cleavage of the P-Se bond to generate the phosphonyl, phosphonothioyl, phosphonodithioyl, or phosphonotrithioyl radicals. Most of these are shown to add onto electron-rich and electron-poor alkenes to deliver the expected adducts in fair to excellent yields. Cyclic precursor 19b displays peculiar behavior and, under the reaction conditions, produces only the corresponding cyclic phosphite. Application of this radical chain process is carried out on furanosyl 3-exo-methylene derivative 37 to diastereoselectively furnish five new 3-phosphonomethyl-, 3-phosphonothiomethyl-, and 3-phosphonodithiomethyl-3-deoxofuranoses 38a-c and 38f,g. The possibility of conducting tandem processes is also discussed through experiments involving (1R)-(+)-alpha-pinene (39) and diallylamine 41.

Hydrolytic reactions of 3'-N-phosphoramidate and 3'-N-thiophosphoramidate analogs of thymidylyl-3',5'-thymidine

The diastereomeric thiophosphoramidate analogs [(R(P))- and (S(P))-3[prime or minute],5[prime or minute]-Tnp(s)T] and the phosphoramidate analog [3[prime or minute],5[prime or minute]-TnpT] of thymidylyl-3[prime or minute],5[prime or minute]-thymidine were prepared and their hydrolytic reactions over the pH-range 1-8 at 363.2 K were followed by RP HPLC. At pH < 6, an acid-catalyzed P-N3[prime or minute] bond cleavage (first-order in [H(+)]) takes place with both 3[prime or minute],5[prime or minute]-Tnp(s)T and 3[prime or minute],5[prime or minute]-TnpT, the former being about 12 fold more stable than the latter. At pH > 4, Tnp(s)T undergoes two competing pH-independent reactions, desulfurization (yielding TnpT) and depyrimidination (cleavage of the N-glycosidic bond) the rates of which are of the same order of magnitude. Also with 3[prime or minute],5[prime or minute]-TnpT the pH-independent depyrimidination competes with P-N3[prime or minute] cleavage at pH > 5.

Development and validation of a liquid chromatographic method for monitoring of process-related synthetic organic impurities of profenofos in technical products

A simple and rapid reversed-phase high-performance liquid chromatographic method for the monitoring of process-related synthetic organic impurities of profenofos (PFS) is developed. Impurities are separated and determined on a reversed-phase Hypersil C(18) column using gradient elution of 50 mM ammonium formate buffer-acetonitrile as a mobile phase and detection at 230 nm at ambient temperature. The method is validated with respect to accuracy, precision, linearity, and limits of detection and quantitation. The method is found to be suitable not only for monitoring the reactions involved in the process development of PFS, but also quality assurance, as it can detect impurities at the level of 1.5 x 10(-8) g.