Surface and structural effects of the agrochemical ethephon on phospholipid mimetic membranes depending on lipid...

Ethephon (2-chloroethylphosphonic acid), a widely used ethylene-releasing agrochemical, raises concerns regarding its potential interactions with biological membranes. To address this, we investigated the effects of ethephon on model phosphatidylcholine membranes with different degrees of unsaturation, employing giant unilamellar vesicles (GUVs) as bilayer systems and Langmuir films as complementary monolayer models. GUVs revealed a clear dependence of membrane response on lipid composition. Saturated DPPC vesicles displayed limited morphological alterations upon exposure to ethephon, whereas unsaturated systems were markedly more sensitive. POPC bilayers showed the strongest response, with rapid onset of structural damage, loss of phase contrast, and vesicle rupture within minutes of exposure. DOPC vesicles were also affected, though to a lesser extent, predominantly through loss of contrast and minor shape deformations. Langmuir film experiments supported these findings, indicating that ethephon preferentially interacts with the polar headgroups of unsaturated lipids and induces disorder in their hydrocarbon chains, as revealed by PM-IRRAS. The combined evidence demonstrates that lipid unsaturation plays a critical role in modulating the susceptibility of membranes to ethephon, with POPC bilayers being the most vulnerable. These results highlight potential molecular mechanisms underlying the impact of this agrochemical on cell membranes and may provide insights into its toxicological effects at the biomembrane level.