Degradation Of Organophosphorus Compounds Research Articles

Uptake, translocation, bioaccumulation, and bioavailability of organophosphate esters in rice paddy and maize fields

Rice and maize are two main crops with different growth habits in Northeast China. To investigate the uptake, translocation, and accumulation of organophosphate esters (OPEs) in those two crops, we measured the OPE concentrations in their agricultural soil-crop systems during different growing seasons. OPE concentrations were higher in paddy (221 ± 62.0 ng/g) than in maize (149 ± 31.6 ng/g) soil, with higher OPE levels in the rhizosphere than in bulk soil for rice, and the opposite in maize. Two-step extractions were used to obtain the labile and stable adsorption components of OPEs. The stable-adsorbed OPEs were activated to be more bioavailable by root exudates as rice grew. OPEs in rice increased linearly with the growing period. The uptake and translocation processes of OPEs by crops were not well-explained by logKow alone, indicating other processes such as growth dilution are significant for understanding OPE levels in plant. The translocation factors of OPEs from nutritive to reproductive organs indicated that OPEs in rice seeds may follow the translocation from root to leaf and then transfer to grains. Two genera, Sphingomonas and Geobacter, associated with degradation of organophosphorus compounds were enriched in rhizosphere soils, indicating enhanced OPE degradation.

Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH3OPO and CH3PO2

AbstractMethoxyphosphinidene oxide (CH3OPO) and isomeric methyldioxophosphorane (CH3PO2) are key intermediates in the degradation of organophosphorus compounds (OPCs). Unlike the nitrogen analogues CH3ONO and CH3NO2, the experimental data for these two prototypical OPCs are scarce. By high‐vacuum flash pyrolysis (HVFP) of the diazide CH3OP(O)(N3)2 at 1000 K, the cis and trans conformers of CH3OPO have been generated in the gas phase and subsequently isolated in cryogenic Ar and N2 matrices for IR spectroscopic characterization. Upon 266 nm laser irradiation of CH3OPO, cis→trans conformational conversion occurs with concurrent isomerization to CH3PO2. The spectroscopic identification of CH3OPO and CH3PO2 is supported by D‐, 13C‐, and 18O‐isotope labeling and quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction (VCI).

Phosphorus Analogues of Methyl Nitrite and Nitromethane: CH3 OPO and CH3 PO2.

Methoxyphosphinidene oxide (CH3 OPO) and isomeric methyldioxophosphorane (CH3 PO2 ) are key intermediates in the degradation of organophosphorus compounds (OPCs). Unlike the nitrogen analogues CH3 ONO and CH3 NO2 , the experimental data for these two prototypical OPCs are scarce. By high-vacuum flash pyrolysis (HVFP) of the diazide CH3 OP(O)(N3 )2 at 1000 K, the cis and trans conformers of CH3 OPO have been generated in the gas phase and subsequently isolated in cryogenic Ar and N2 matrices for IR spectroscopic characterization. Upon 266 nm laser irradiation of CH3 OPO, cis→trans conformational conversion occurs with concurrent isomerization to CH3 PO2 . The spectroscopic identification of CH3 OPO and CH3 PO2 is supported by D-, 13 C-, and 18 O-isotope labeling and quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction (VCI).

Asymmetric biodegradation of the nerve agents Sarin and VX by human dUTPase: chemometrics, molecular docking and hybrid QM/MM calculations

Organophosphorus compounds (OP) nerve agents are among the most toxic chemical substances known. Their toxicity is due to their ability to bind to acetylcholinesterase. Currently, some enzymes, such as phosphotriesterase, human serum paraoxonase 1 and diisopropyl fluorophosphatase, capable of degrading OP, have been characterized. Regarding the importance of bioremediation methods for detoxication of OP, this work aims to study the interaction modes between the human human deoxyuridine triphosphate nucleotidohydrolase (dUTPase) and Sarin and VX, considering their Rp and Sp enantiomers, to evaluate the asymmetric catalysis of those compounds. In previous work, this enzyme has shown good potential to degrade phosphotriesters, and based on this characteristic, we have applied the human dUTPase to the OP degradation. Molecular docking, chemometrics and mixed quantum and molecular mechanics calculations have been employed, showing a good interaction between dUTPase and OP. Two possible reaction mechanisms were tested, and according to our theoretical results, the catalytic degradation of OP by dUTPase can take place via both mechanisms, beyond being stereoselective, that is, dUTPase cleaves one enantiomer preferentially in relation to other. Chemometric techniques provided excellent assistance for performing this theoretical investigation. The dUTPase study shows importance by the fact of it being a human enzyme.Communicated by Ramaswamy H. Sarma

Identification and characterization of a novel phosphodiesterase from the metagenome of an Indian coalbed.

Phosphoesterases are involved in the degradation of organophosphorus compounds. Although phosphomonoesterases and phosphotriesterases have been studied in detail, studies on phosphodiesterases are rather limited. In our search to find novel phosphodiesterases using metagenomic approach, we cloned a gene encoding a putative phosphodiesterase (PdeM) from the metagenome of the formation water collected from an Indian coal bed. Bioinformatic analysis showed that PdeM sequence possessed the characteristic signature motifs of the class III phosphodiesterases and phylogenetic study of PdeM enabled us to identify three distinct subclasses (A, B, and C) within class III phosphodiesterases, PdeM clustering in new subclass IIIB. Bioinformatic, biochemical and biophysical characterization of PdeM further revealed some of the characteristic features of the phosphodiesterases belonging to newly described subclass IIIB. PdeM is a monomer of 29.3 kDa, which exhibits optimum activity at 25°C and pH 8.5, but low affinity for bis(pNPP) as well as pNPPP. The recombinant PdeM possessed phosphodiesterase, phosphonate-ester hydrolase and nuclease activity. It lacked phosphomonoesterase, phosphotriesterase, and RNAse activities. Overexpression of PdeM in E.coli neither affected catabolite respression nor did the recombinant protein hydrolyzed cAMP in vitro, indicating its inability to hydrolyze cAMP. Although Mn2+ was required for the activity of PdeM, but addition of metals (Mn2+ or Fe3+) did not induce oligomerization. Further increase in concentration of Mn2+ upto 3 mM, increased α-helical content as well as the phosphodiesterase activity. Structural comparison of PdeM with its homologs showed that it lacked critical residues required for dimerization, cAMP hydrolysis, and for the high affinity binding of bis(pNPP). PdeM, thus, is a novel representative of new subclass of class III phosphodiesterases.

Organophosphorus compound detection on a cell chip with yeast coexpressing hydrolase and eGFP

Organophosphorus compounds (OPs) such as pesticides, fungicides, and herbicides are highly toxic but are nevertheless extensively used worldwide. To detect OPs, we constructed a yeast strain that co-displays organophosphorus hydrolase (OPH) and enhanced green fluorescent protein (EGFP) on the cell surface using a Flo1p anchor system. OP degradation releases protons and causes a change in pH. This pH change results in structural deformation of EGFP, which triggers quenching of its fluorescence, thereby making this cell useful for visual detection of OPs. Fluorescence microscopy confirmed the high-intensity fluorescence displayed by EGFP on the cell surface. The yeast strain possessed sufficient OPH hydrolytic activities for degrading OPs, as measured by incubation with 1 mM paraoxon for 24 h at 30 degrees C. In addition, with 20 mM paraoxon at 30 degrees C, fluorescence quenching of EGFP on the single yeast cell was observed within 40 s in a microchamber chip. These observations suggest that engineered yeast cells are suitable for simultaneous degradation and visual detection of OPs.

Degradation of organophosphorus compounds by X-ray irradiation

The degradation of organophosphorus pesticide diazinon in aqueous media with a white X-ray beam from a conventional X-ray source was studied. The concentration of the pesticide in the solution (40 mg dm −3) decreases exponentially with the exposure time, i.e. with the absorbed dose: 50% degradation is obtained at the dose of about 160 Gy. The compounds detected in the irradiation samples suggest that diazinon is converted mainly into 2-isopropyl-4-methyl-6-hydroxypyrimidine, which is also its main hydrolysis product.

Laser‐induced degradation of organophosphorus compounds

The object of our research has been laser‐induced photo‐oxidation of organophosphorus compounds in aqueous media. A XeCl excimer laser with a pulse energy of up to 150 mJ and wavelength of 308 nm has been used as a light source. The research comprised the influence of irradiation conditions on pesticide degradation (number of laser pulses, pulse energy) and decomposition efficiency. The time between irradiation and sample isolation ranged from 5 min to 24 hrs. Rapid decomposition has been achieved within two hours following the irradiation for the range of concentrations limited by the solubility of pesticide (up to 40 mgL-1). 1 mL samples required less than 120 mJ of total irradiation energy at 308 nm, which was delivered to the sample in time intervals shorter then 1 second when catalysts, such as titanium dioxide and hydrogen peroxide were applied. Similar degradation efficiency was also obtained without the addition of catalysts when higher irradiation energies were used. The compounds detected in the irradiated samples suggest that diazinon is converted directly into 2‐isopropyl‐4‐methyl‐6‐hydroxypyrimidine without the formation of more toxic diazoxon. This transformation involves oxidation of the sulphur atom to the sulphate anion.

Persistence of organophosphorus insecticides in sewage sludges

Abstract The stability of three selected organophosphorus in raw and chemically conditioned sewage sludges has been investigated. Results indicate that certain of these compounds will degrade in raw sludges and degrade rapidly in conditioned sludges. The possible roles of additional factors in the degradation of organophosphorus compounds in the environment are discussed.

Mechanism of detoxication of some organophosphorus compounds: the role of glutathione-dependent demethylation.

The detoxication of the geometrical isomers of Bomyl® (dimethyl-1,3-dicarbomethoxy-1-propen-2-yl phosphate) and Phosdrin® (mevinphos, dimethyl-1-carbomethoxy-1-propen-2-yl phosphate) by mouse liver has been studied. Most of the degrading activity for Phosdrin isomers was found in the supernatant fraction, whereas for Bomyl isomers it was equally distributed between the microsomal and the supernatant fractions. cis-Phosdrin is degraded in a system which requires reduced glutathione, the metabolites being cis-monomethyl-1-carbomethoxy-1-propen-2-yl phosphate (cis-desmethyl-Phosdrin)and S-methylglutathione. On the other hand, tras-Phosdrin and both Bomyl isomers were degraded to dimethyl phosphate. A method for the synthesis of cis-thiono-Bomyl is also reported. The possible general role of glutathione in the degradation of organophosphorus compounds is discussed.