Partition of 2,4-dichlorophenoxyacetic acid derivatives in phosphatidylcholine multi-lamellar vesicles

The interaction of 2,4-dichlorophenoxyacetic acid (2,4-D) with multi-lamell ar vesicles of dimyristyl and dipalmitoyl L-alpha -phosphatidylcholine as e xamined from the pH dependeny of partition and pH-and emperature-dependent polarization of fluorescence probes such as 1,6-diphenyl-1,3,5-hexatriene. It strongly suggested that 2,4-D in the undissociated form as located at th e region from the neighborhood of the glycerol backbone to a shallops site of the hydrophobic core of the lipid bilayers and that its anionic species was adsorbed at the membrane surface. Fluorescence studs with the derivativ es of 2,4-D showed that hydrophobicity and pKa of these acids, determined t heir interaction kith membrane.