title: Phase diagram of a polyunsaturated lipid mixture: Brain sphingomyelin/1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine/cholesterol.
abstract: Phospholipids having a polyunsaturated acyl chain are abundant in biological membranes, but their behavior in lipid mixtures is difficult to study. Here we elucidate the nature of such mixtures with this report of the first ternary phase diagram containing the polyunsaturated lipid SDPC in mixtures of BSM/SDPC/Chol (brain sphingomyelin/1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine/cholesterol). These mixtures show coexisting macroscopic liquid-disordered (Ld) and liquid-ordered (Lo) phase separation, with phase boundaries determined by FRET and by fluorescence microscopy imaging of giant unilamellar vesicles (GUVs). Surprisingly, SDPC mixes with BSM/Chol similarly to how DOPC and POPC mix with BSM/Chol. Notably, intermediate states are produced within the Ld+Lo liquid-liquid immiscibility region upon addition of fourth component POPC. These mixtures of BSM/SDPC/POPC/Chol exhibit nanoscopic Ld+Lo domains over a very large volume of composition space, possibly because Ld/Lo line tension is not high.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Tatyana M
authors.initials: TM
authors.lastname: Konyakhina
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA. Electronic address: gwf3@cornell.edu.
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Feigenson
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002784:Cholesterol / Q000737:chemistry* / Q000302:isolation & purification; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000302:isolation & purification; D013109:Sphingomyelins / Q000737:chemistry* / Q000302:isolation & purification; D013552:Swine; D053835:Unilamellar Liposomes / Q000737:chemistry*
chemical_list: C409542:1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine; D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D053835:Unilamellar Liposomes; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine
keywords: Lipid rafts; Modulated phases; Polyunsaturated lipid; SDPC PUFA lipid; Ternary lipid phase diagram