Partition of DDE in synthetic and native membranes determined by ultraviolet derivative spectroscopy

Abstract

Partition coefficients of DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethylene) were determined, in model and native membranes, as a function of temperature, lipid chain length, cholesterol content and DDE concentration, by means of second derivative ultraviolet spectrophotometry. DDE incorporation increases with the temperature, since the partition values in dimyristoylphosphatidylcholine (DMPC), at 24, 30 and 37 degrees C, are 5722 +/- 138, 10356 +/- 763 and 14006 +/- 740, respectively. The insecticide incorporates better into bilayers of DMPC as compared with DPPC (dipalmitoylphosphatidylcholine). The partition decreases from 10355 +/- 763 in DMPC to 6432 +/- 613 in DPPC, at temperatures 5-7 degrees C above the midpoint of their transitions. The addition of cholesterol to fluid membranes of DMPC depresses the partition of DDE. In agreement with the results in models of synthetic lipids, the partition of DDE into native membranes increases with the temperature and decreases with the intrinsic cholesterol. It is concluded that a fluid membrane favors the accumulation of DDE.

Partition of DDT and DDE into Membranes and Extracted Lipids of Bacillus stearothermophilus

“…Independently of temperature, DDT and DDE incorporated in higher yields into bilayers of polar lipids compared to bilayers of the total lipid fraction. These observations confirm previous studies (Antunes-Madeira and Madeira 1989: Videira et al 1995) indicating that the specific lipid composition of the bilayer influences partitioning to some extent. Therefore, incorporation of DDT and DDE (and presumably other xenobiotics) is optimized at a certain degree of lipid order, dependent on the temperature and lipid composition.…”

“…Preferential incorporation of DDT also occurred in the native membranes, as described above for lipid membranes. Higher partitionings of DDT relative to DDE have also been described previously for other membrane types (Antunes-Madeira and Madeira 1986; Videira et al 1995). Partition coefficients of DDT into membranes of mitochondria and sarcoplasmic reticulum at 15 °C are 8 x 10 5 and 11 x 10 5 , respectively, as compared with 9.6 x 10 4 and 4.6 x 1 0 4 for DDE.…”

“…Therefore, incorporation of DDT and DDE (and presumably other xenobiotics) is optimized at a certain degree of lipid order, dependent on the temperature and lipid composition. Furthermore, the total lipid fraction contains carotenoids and/or hopanoids that, similarly to cholesterol in other membranes (Antunes-Madeira and Madeira 1986;Videira et al 1995), may change the membrane organization in such a way that the free volume for xenobiotic incorporation and interaction decreases.…”

“…Additionally, the increased inhibition of respiration enzymes by DDT as compared with DDE parallels its higher inhibitory effect on bacterial growth, indicating a higher level of toxicity of the former compound. These results induced us to study the partition of DDT and DDE into bacterial membranes, since it has been only determined in models of synthetic lipids and in native membranes of eukaryotic cells (Antunes-Madeira and Madeira 1986;Videira et al 1995). Therefore, the partition of DDT and DDE into bacterial membranes would be relevant to relate membrane effects to the actual bilayer concentration.…”

Comparative effects of herbicide dicamba and related compound on plant mitochondrial bioenergetics

“…At higher concentrations like those used in our experiments, some dicamba can certainly incorporate into the membrane, the aromatic portion being immersed into the hydrophobic part, whereas the polar portion of the molecule remains in the hydrophilic surface. In fact, we tried to measure the partition of dicamba and 2-chlorobenzoic acid into submitochondrial particles, using a spectroscopic method described by Videira et al [27], but it was impossible to measure because the level of incorporation was very small.…”