PubMed · 4925792
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J T Lynch, G D Smith. 1971-03-19. Scientific inofrmation by computer.. https://doi.org/10.1038/230153a0
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Organophosphorus pesticides are the most common classes involved in poisonings related to pesticides. We used enzymatic activity of chloroperoxidase on the metabolism of some phosphorothioate pesticides published previously and molecular mechanics methods to perform a theoretical approach of the mechanism of biological oxidation of this class of pesticides. The molecular structure of eight pesticides were optimized by molecular mechanics methods using the CAChe program package for biomolecules, ver. 3.11 (Oxford Molecular Ltd., Campbell, CA). Total energy resulted from the structure optimization process and the partial charges of both phosphorus and sulfur were computed for every pesticide. Phosphorus partial charge and enzymatic activity were significantly related by linear regression analysis (r=0.82, P<0.05). Analyzing our results and using previously reported enzymatic activity of chloroperoxidase on these pesticides, we deduced chemical events involved in activation of the active site of chloroperoxidase and proposed a novel mechanism of oxidation for this class of pesticides. This mechanism will also help to understand the oxidation process of pesticides by cytochrome P450, and production of toxic metabolites.
Solid-phase microextraction (SPME) has recently been applied to measure the freely dissolved concentration, as opposed to the total concentration, of hydrophobic substances in aqueous solutions. This requires that only the freely dissolved analytes contribute to the concentration in the SPME fiber coating. However, for nonequilibrium SPME the sorbed analytes that diffuse into the unstirred water layer (UWL) adjacent to the SPME fiber can desorb from the matrix and contribute to the flux into the fiber. These processes were described as a model. Experimentally, an equilibrated and disconnected headspace was used as a reference for the freely dissolved concentration. The expected contribution of desorbed analytes to the uptake flux was measured for PCB no. 52 in a protein-rich solution, while it was not measured in a matrix containing artificial soil. The latter was possibly due to slow desorption of the analyte from the artificial soil. On the basis of the present study, a contribution of desorbed analytes to the uptake flux is expected only if(1) the rate-limiting step of the uptake process is diffusion through the UWL, (2) the concentration of the sorbed analyte is high, and (3) desorption from the matrix is fast.
The ability of supercritical water (SCW) to decompose heterocyclic compounds (quinoline and isoquinoline) has been explored in this study. The results obtained suggest that water acts as a chemical reagent above its critical point (374 degrees C and 22.1 MPa). Significant proportions of isoquinoline and quinoline were removed during the reaction with SCW. The response of these compounds to pyrolysis was also compared with their reaction with SCW. Both compounds were relatively more reactive in the presence of SCW than during pyrolysis. Because of the different positions of N atom in the two compounds, they reacted with SCW differently. Breaking of C-N bonds during SCW reaction was by hydrogenation and hydrocracking, while pyrolysis was due to thermocracking mainly.