Phthalic acid esters, and in particular bis-2-(ethylhexyl) phthalate, are common environmental contaminants with long-term
toxic and carcinogenic effects that readily dissolve in lipid substances. DSC measurements of hydrated multilamellar dipalmitoyl
phosphatidylcholine liposomes in the presence of different amounts of bis-2-(ethylhexyl) phthalate, dioctyl phthalate, dibutyl
phthalate (DBP) and diethyl phthalate (DEP) were considered. The effects on the main transition temperature, ΔH, and the shape
and width of the transition were studied.
A decrease in Tm, without an accompanying decrease in ΔH,and increases in both the asymmetry and the width of the main transition peak were
In some cases, the calorimetric curve showed complex peak structures arising from the coexistence of various aggregates of
different sizes. This was particularly evident in the liposomes with DEP and DBP contents ranging from 5.0 to 7.5% m/m.
For all the considered model systems, the effects were noticeable even in the presence of small amounts of phthalates; in
the presence of greater amounts, the overall structure of the bilayer was in some cases strongly modified, with the appearance
of new different phases.
Since the function of a membrane-associated protein is dependent on the lipid structure, phthalates could modify the function
by modifying the membrane structure.