title: Deuterium NMR of raft model membranes reveals domain-specific order profiles and compositional distribution.
abstract: In this report, we applied site-specifically deuterated N-stearoylsphingomyelins (SSMs) to raft-exhibiting ternary mixtures containing SSM, 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol (Chol) and successfully acquired deuterium quadrupole coupling profiles of SSM from liquid-ordered (Lo) and liquid-disordered (Ld) domains. To our knowledge, this is the first report that shows detailed lipid chain dynamics separately and simultaneously obtained from coexisting Lo and Ld domains. We also found that the quadrupole profile of the Lo phase in the ternary system was almost identical to that in the SSM-Chol binary mixture, suggesting that the order profile of the binary system is essentially applicable to more complicated membrane systems in terms of the acyl chain order. We also demonstrated that (2)H NMR spectroscopy, in combination with organic synthesis of deuterated components, could be used to reveal the accurate mole fractions of each component distributed in the Lo and Ld domains. As compared with the reported tie-line analysis of phase diagrams, the merit of our (2)H NMR analysis is that the domain-specific compositional fractions are directly attainable without experimental complexity and ambiguity. The accurate compositional distributions as well as lipid order profiles in ternary mixtures are relevant to understanding the molecular mechanism of lipid raft formation.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan; Japan Science and Technology Agency, ERATO, Lipid Active Structure Project, Toyonaka, Osaka, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsuchikawa
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan; Japan Science and Technology Agency, ERATO, Lipid Active Structure Project, Toyonaka, Osaka, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Murata
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan. Electronic address: matsmori@chem.kyushu-univ.jp.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Matsumori
mesh_terms: D002784:Cholesterol / Q000737:chemistry; D003903:Deuterium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D021962:Membrane Microdomains / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry
chemical_list: D010713:Phosphatidylcholines; D013109:Sphingomyelins; C033173:N-stearoylsphingomyelin; D002784:Cholesterol; D003903:Deuterium; C017251:1,2-oleoylphosphatidylcholine