Using Curvature Power To Map the Domain of Inverse Micellar Cubic Phases: The Case of Aliphatic Aldehydes in 1,2-Dioleoyl-<i>sn</i>-glycero-3-phosphoethanolamine

Oxylipins, or fatty aldehydes, are a class of molecules produced from membrane lipids as a result of oxidative stress or enzyme-mediated peroxidation. Here we report the effects of two biologically important fatty aldehydes, <i>trans</i>,<i>trans</i>-2,4-decanedienal (DD) and <i>cis</i>-11-hexadecenal (HD), on the phase behavior of the lipid 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphoethanolamine (DOPE) in water. We compare the phase behavior of DD/DOPE and HD/DOPE mixtures to the phase behavior of oleic acid/DOPE mixtures and show that DD, HD, and oleic acid have similar effects on the phase diagrams of DOPE. Notably, both DD and HD, like oleic acid, induce the formation of <i>Fd</i>3<i>m</i> inverse micellar cubic phases in DOPE/water mixtures. This is the first time that <i>Fd</i>3<i>m</i> phases in fatty aldehyde-containing mixtures have been reported. We assess the effects of DD, HD, and oleic acid on DOPE in terms of lipid spontaneous curvatures and propose a method to predict the formation of <i>Fd</i>3<i>m</i> phases from the curvature power of amphiphiles. This methodology predicts that <i>Fd</i>3<i>m</i> phases will become stable if the spontaneous curvature of a lipid mixture is −0.48 ± 0.05 nm^–1 or less