Enhanced nucleophilic reactivity of hydroxamate ions in some novel micellar systems for the cleavage of Parathion

β-Cyclodextrin Stabilized Nanoceria for Hydrolytic Cleavage of Paraoxon in Aqueous and Cationic Micellar Media

Beta-cyclodextrin (β-CD) stabilized cerium oxide nanoparticles (β-CD@CeO₂ NPs) were synthesized through a hydrothermal route. The electronic properties, surface functional group, surface composition, size, and morphologies of the as-synthesized β-CD@CeO₂ NPs were characterized using UV-visible spectroscopy, FTIR analysis, high resolution X-ray photoelectron spectroscopy (HRXPS), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). The pH-dependent variation of the ζ-potential of β-CD@CeO₂ NPs and the catalytic activity of the NPs for the hydrolysis of paraoxon were investigated. The observed pseudo-first-order rate constant (k_obs) for the hydrolysis of paraoxon is increased with increasing pH and the ζ-potential of β-CD@CeO₂ NPs. The kinetics and mechanism of hydrolysis of paraoxon in the aqueous and cationic micellar media have been discussed.

Synthesis and biological evaluation of aryl phosphoramidate prodrugs of fosfoxacin and its derivatives

Aryl phosphoramidate prodrugs of fosfoxacin derivatives 15a-b and 8a-b were synthesized and investigated for their ability to target bacteria. No growth inhibition was observed neither for Mycobacterium smegmatis nor for Escherichia coli on solid medium, demonstrating the absence of release of the active compounds in the bacterial cells. Investigation of the stability of the prodrugs and their multienzymatic cleavage in abiotic and biotic conditions showed that the use of aryl phosphoramidate prodrug approach to deliver non-nucleotides compounds is not obvious and might not be appropriate for an antimicrobial drug.

From α-nucleophiles to functionalized aggregates: exploring the reactivity of hydroxamate ion towards esterolytic reactions in micelles

Hydroxamate ions as α-nucleophiles for esterolytic reactions in water and micelles.

Parathion hydrolysis revisited: in situ aqueous kinetics by (1)h NMR

The kinetics of parathion (PTH) decomposition into para-nitrophenolate (pNP) and O,O-diethylthiophosphate (DETP) were measured in high-pH aqueous solutions at 20 °C by proton nuclear magnetic resonance spectroscopy ((1)H NMR). Reaction rates were determined over a 16 h observation time, in solutions with NaOD concentrations of 5.33 mM, 33.33 mM, and 100 mM, with NaCl added to fix ionicity. The pseudo-first-order rate constants for these systems were determined to be 1.9 × 10(-4) min(-1), 1.4 × 10(-3) min(-1), and 3.8 × 10(-3) min(-1) respectively. The slope of the linear plot of these rates against OD(-) concentration yielded the second-order hydrolysis rate constant 3.90 × 10(-5) mM(-1) min(-1), valid over this pH range from 10.5 to 13. The data agree with some, and contradict other, earlier work. Our fitting procedure included background levels and allowed us to not only obtain reliable kinetic results but also to measure residual pNP and DETP impurity levels.

Dynamics and Orientation of Parathion Dissolved in a Discotic Nematic Lyomesophase

Parathion, an organophosphorous pesticide, presents serious hazards to the environment and health. It inhibits acetylcholinesterase, an enzyme incorporated in the cell membrane. A study on the behaviour of parathion in a lipid environment is interesting from environmental cleaning and biological perspectives. 2H NMR quadrupole splittings (ΔνQ) and longitudinal relaxation times (T1) of parathion-d4, dissolved in a nematic discotic lyomesophase made of tetradecyltrimethylammonium chloride/decanol (10% 1,1-dideuterodecanol)/water (0.1% D2O)/NaCl, have been measured. ΔνQ and T1 from DHO and 1,1-dideuterodecanol were also obtained. For a detailed understanding of the experimental results, a 19 ns molecular dynamics (MD) simulation of a bilayer fragment including three parathion molecules was calculated. Parathion is strongly attached to the aggregate and the solubilization increases the alignment of the interface components. Calculated densities show that parathion is located in the hydrophobic core, near the interface, and experiences an electrostatic interaction with the ammonium headgroups. On average, the molecule orients with the ring plane containing the bilayer normal.