Line tension between domains in multicomponent membranes is sensitive to degree of unsaturation of hybrid lipids

Hybrid lipids (with one saturated tail and one unsaturated tail) have been proposed as agents that can reduce the line tension between domains. We use a liquid crystal model to predict the effect of the degree of unsaturation in the unsaturated tails of hybrid lipids on the miscibility phase diagram and line tension between domains in membranes comprising saturated lipids (with two saturated tails), hybrid lipids, and cholesterol (SHC membranes). In contrast to SHC membranes containing hybrid lipids with a single (or small) degree of unsaturation, for which the phase diagram shows two distinct two-phase regions, SHC membranes containing hybrid lipids with degrees of unsaturation larger than a threshold value exhibit a single two-phase region. This enables hybrid lipids with larger degrees of unsaturation to steadily increase their chain order with decreasing temperature and enhances the reduction of the line tension. This theory predicts that the line tension between domains in SHC membranes is sensitive to the degrees of unsaturation of hybrid lipids.