title: Comparison of three ternary lipid bilayer mixtures: FRET and ESR reveal nanodomains.
abstract: Phase diagrams of ternary lipid mixtures containing cholesterol have provided valuable insight into cell membrane behaviors, especially by describing regions of coexisting liquid-disordered (Ld) and liquid-ordered (Lo) phases. Fluorescence microscopy imaging of giant unilamellar vesicles has greatly assisted the determination of phase behavior in these systems. However, the requirement for optically resolved Ld + Lo domains can lead to the incorrect inference that in lipid-only mixtures, Ld + Lo domain coexistence generally shows macroscopic domains. Here we show this inference is incorrect for the low melting temperature phosphatidylcholines abundant in mammalian plasma membranes. By use of high compositional resolution Förster resonance energy transfer measurements, together with electron spin resonance data and spectral simulation, we find that ternary mixtures of DSPC and cholesterol together with either POPC or SOPC, do indeed have regions of Ld + Lo coexistence. However, phase domains are much smaller than the optical resolution limit, likely on the order of the Förster distance for energy transfer (R(0), ∼2-8 nm).
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA.
authors.forename: Frederick A
authors.initials: FA
authors.lastname: Heberle
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.forename: Shih Lin
authors.initials: SL
authors.lastname: Goh
authors.forename: Robin S
authors.initials: RS
authors.lastname: Petruzielo
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Feigenson
mesh_terms: D002784:Cholesterol / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004875:Ergosterol / Q000031:analogs & derivatives / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D008051:Lipid Bilayers / Q000737:chemistry*; D021962:Membrane Microdomains / Q000737:chemistry*; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D011162:Porphobilinogen / Q000031:analogs & derivatives / Q000737:chemistry; D013499:Surface Properties
chemical_list: C538930:3-anilino difluoroboron dipyrromethene; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; C010905:dehydroergosterol; C027891:1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine; D011162:Porphobilinogen; D002784:Cholesterol; C010942:1,2-distearoyllecithin; C017251:1,2-oleoylphosphatidylcholine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D004875:Ergosterol