title: The Long-Chain Sphingoid Base of Ceramides Determines Their Propensity for Lateral Segregation.
abstract: We examined how the length of the long-chain base or the N-linked acyl chain of ceramides affected their lateral segregation in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. Lateral segregation and ceramide-rich phase formation was ascertained by a lifetime analysis of trans-parinaric acid (tPA) fluorescence. The longer the length of the long-chain base (d16:1, d17:1, d18:1, d19:1, and d20:1 in N-palmitoyl ceramide), the less ceramide was needed for the onset of lateral segregation and ceramide-rich phase formation. A similar but much weaker trend was observed when sphingosine (d18:1)-based ceramide had N-linked acyl chains of increasing length (14:0 and 16:0-20:0 in one-carbon increments). The apparent lateral packing of the ceramide-rich phase, as determined from the longest-lifetime component of tPA fluorescence, also correlated strongly with the long-chain base length, but not as strongly with the N-acyl chain length. Finally, we compared two ceramide analogs with equal carbon numbers (d16:1/17:0 or d20:1/13:0) and observed that the analog with a longer sphingoid base segregated at lower bilayer concentrations to a ceramide-rich phase compared with the shorter sphingoid base analog. The gel phase formed by d20:1/13:0 ceramide also was more thermostable than the gel phase formed by d16:1/17:0 ceramide.2H NMR data for 10 mol % stearoyl ceramide in POPC also showed that the long-chain base was more ordered than the acyl chain at comparable chain positions and temperatures. We conclude that the long-chain base length of ceramide is more important than the acyl chain length in determining the lateral segregation of the ceramide-rich gel phase and intermolecular interactions therein.
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland.
authors.forename: Md Abdullah
authors.initials: MA
authors.lastname: Al Sazzad
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland; Department of Organic Chemistry, Graduate School of Science, University of Osaka, Osaka, Japan.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Yasuda
authors.affiliation: Department of Organic Chemistry, Graduate School of Science, University of Osaka, Osaka, Japan.
authors.forename: Michio
authors.initials: M
authors.lastname: Murata
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland. Electronic address: jpslotte@abo.fi.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D002518:Ceramides / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry*
chemical_list: D002518:Ceramides; D010713:Phosphatidylcholines; C028694:1-palmitoyl-2-oleoylphosphatidylcholine