Partition of 2, 4-Dichiorophenoxyacetic Acid Derivatives in Phosphatidyicholine Multi-lamellar Vesicles

Abstract

The interaction of 2, 4-dichlorophenoxyacetic acid (2, 4-D) with multi-lamellar vesicles of dimyristoyl and dipalmitoyl L-a-phosphatidylcholine was examined from the pH dependency of partition and pHand temperature-dependent polarization of fluorescence probes such as 1, 6-Biphenyl-1, 3, 5-hexatriene. It was strongly suggested that 2, 4-D in the undissociated form was located at the region from the neighborhood of the glycerol backbone to a shallow site of the hydrophobic core of the lipid bilayers and that its anionic species was adsorbed at the membrane surface. Fluorescence study with the derivatives of 2, 4-D showed that hydrophobicity and pKa of these acids determined their interaction with membrane.

Theoretical and organic chemical approaches to environmental behavior and metabolism of pesticides

“…A similar approach with the additional fluorescence probe chlorophyll a was taken for the partition of phenoxyalkanoic acid herbicides to the MLV, and the undissociated 2,4-D was shown to reside in the hydrophilic region of DPPC bilayer. 19) This phenomenon was in good agreement with the uptake profiles of carboxylic acid metabolites of pesticides by duckweed (Lemna gibba). 20)…”

Modeling Kinetics of Subcellular Disposition of Chemicals

“…This phenomenon is caused by the interactions with the headgroups of neutral and acidic phospholipids, which lead to a rearrangement in the headgroups. 541,542 The former profiles are still rather shallow in comparison with those for the 1-octanol/water partition coefficients (P O/W ). The differences of the P B/W values for different pH of the aqueous phases are dependent on the ionization character of the chemical: they are comparatively small for bases and can reach a magnitude100-fold larger for acids.…”

“…If more-diverse chemicals were considered, the relationship seemed to hold, with a broader scatter and within certain size and lipophilicity limits, , for neutral molecules but not for charged molecules. , The differences are more significant for acids, as opposed to bases, because the former show more-pronounced pH dependences of the bilayer/water partition coefficients ( P B/W ) than the latter. This phenomenon is caused by the interactions with the headgroups of neutral and acidic phospholipids, which lead to a rearrangement in the headgroups. , The former profiles are still rather shallow in comparison with those for the 1-octanol/water partition coefficients ( P O/W ). The differences of the P B/W values for different pH of the aqueous phases are dependent on the ionization character of the chemical: they are comparatively small for bases and can reach a magnitude100-fold larger for acids .…”

Dose metric considerations in in vitro assays to improve quantitative in vitro–in vivo dose extrapolations

“…The partitioning of positively charged chemicals to membranes is similar or even enhanced compared to that of neutral compounds with equal hydrophobicity towards cell membranes or microsomes (Austin et al, 1995(Austin et al, , 2002Escher and Schwarzenbach, 1996;Kramer et al, 1998;Schmitt, 2008). An explanation is the attraction of these chemicals to the negative charges of the phospholipids present in membranes (Katagi, 2001). In contrast, negatively charged chemicals are repelled by the anionic surface of membranes.…”