Docosahexaenoic Acid Enhances Segregation of Lipids between Raft and Nonraft Domains: 2H-NMR Study

Solid-state 2H-NMR of [2H31]-N-palmitoylsphingomyelin ([2H31]16:0SM, PSM*), supplemented by differential scanning calorimetry, was used for the first time, to our knowledge, to investigate the molecular organization of the sphingolipid in 1:1:1mol mixtures with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (16:0–18:1PE, POPE) or 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (16:0–22:6PE, PDPE) and cholesterol. When compared with 2H-NMR data for analogous mixtures of [2H31]16:0–18:1PE (POPE*) or [2H31]16:0-22:6PE (PDPE*) with egg SM and cholesterol, molecular interactions of oleic acid (OA) versus docosahexaenoic acid (DHA) are distinguished, and details of membrane architecture emerge. SM-rich, characterized by higher-order, and PE-rich, characterized by lower-order, domains