title: Formation of Gel-like Nanodomains in Cholesterol-Containing Sphingomyelin or Phosphatidylcholine Binary Membrane As Examined by Fluorescence Lifetimes and (2)H NMR Spectra.
abstract: In this study, we measured the time-resolved fluorescence of trans-parinaric acid (tPA), steady-state fluorescence anisotropy of diphenylhexatriene (DPH), and (2)H NMR of 10,10-d2-stearoyl lipids in stearoyl sphingomyelin with cholesterol (SSM/Chol) and l-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine with Chol (PSPC/Chol) binary membranes. The results suggest that the membrane order obtained from the fluorescence experiments shows a similar temperature dependency as those of the (2)H NMR data. More importantly, the time-resolved fluorescence data implied the presence of at least two types of domains, cholesterol-poor gel-like domains (CPGLD) and cholesterol-enriched liquid-ordered (Lo) domains. These domains appear on a nano-to-micro second time scale for both SSM-Chol and PSPC-Chol membranes. The relative size of the gel-like domain was also estimated from the temperature-dependent lifetime measurements and (2)H NMR spectral changes. The results imply that the size of the gel-like domains is very small, probably on the nanometer scale, and smaller in SSM-Chol membrane than those in PSPC-Chol bilayers, which could account for the higher thermal stability of SM-Chol membranes. The present study demonstrates that gel-like nanodomains occur in SM-Chol binary membrane even with Chol content of over 33 mol %, which has been thought to consist exclusively of Lo phase, implying that not only Lo domains but also gel-like nanodomains are important for formation of lipid-ordered phase in SM-Chol and PC-Chol membranes.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan.|Japan Science and Technology Agency, ERATO, Lipid Active Structure Project, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan.|Department of Chemistry, Graduate School of Sciences, Kyushu University , Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Matsumori
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsuchikawa
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Tykistökatu 6A, FIN-20520 Turku, Finland.
authors.forename: Max
authors.initials: M
authors.lastname: Lönnfors
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Tykistökatu 6A, FIN-20520 Turku, Finland.
authors.forename: Thomas K M
authors.initials: TK
authors.lastname: Nyholm
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Tykistökatu 6A, FIN-20520 Turku, Finland.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan.|Japan Science and Technology Agency, ERATO, Lipid Active Structure Project, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Murata
mesh_terms: D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002784:Cholesterol / Q000737:chemistry*; D005453:Fluorescence; D005782:Gels / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D010713:Phosphatidylcholines / Q000737:chemistry*; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature
chemical_list: D005782:Gels; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D002784:Cholesterol