Counterion Effects and Dynamics of Parathion in Anionic Lyomesophases
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Bahamonde, Víctor
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Counterion Effects and Dynamics of Parathion in Anionic Lyomesophases
Abstract
Ingestion of parathion produces catastrophic effects on mammals. Transformed into paraoxon, it inhibits acetylcholinesterase,
producing acetylcholine accumulation. The distribution, orientation, and dynamics of parathion in
different hydrophobic bilayer environments is interesting from both ecological and biological perspectives. A study of
parathion-d4 dissolved in two nematic discotic lyotropic liquid crystals made of sodium and cesium decylsulfate (CsDS
and NaDS)/decanol (10% 1,1-dideuterodecanol)/water (0.1% D2O)/M2SO4 (M=Na+, Cs+), is presented. Deuterium
quadrupole splittings and relaxation times of all deuteriated species were measured. Parathion is strongly attached to both
aggregates, increasing the alignment of CsDS and decreasing the alignment of NaDS. Molecular dynamics trajectories
were calculated for both mesophases. CsDS appears more neutralized than NaDS. Despite the surface charge, parathion
is associated to both aggregates, located near the interface, with the nitro group oriented to the headgroups and the ethoxy
chains toward the hydrophobic core. When included in the CsDS interface, it stabilizes the system by shielding repulsive
electrostatic interactions among headgroups. Included in NaDS, parathion induces an increase in the distance among
counterions and sulfate headgroups, thus decreasing the degree of order.
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The authors acknowledge financial assistance from Fondecyt, Grant
1095175, and Facultad de Ciencias de la Universidad de Chile.Victor Bahamonde
acknowledges a Doctoral Fellowship from Conicyt.
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AUSTRALIAN JOURNAL OF CHEMISTRY, Volume: 63, Issue: 1, Pages: 68-74, 2010
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