title: Importance of the sphingoid base length for the membrane properties of ceramides.
abstract: The sphingoid bases of sphingolipids, including ceramides, can vary in length from 12 to >20 carbons. To study how such length variation affects the bilayer properties of ceramides, we synthesized ceramides consisting of a C12-, C14-, C16-, C18-, or C20-sphing-4-enin derivative coupled to palmitic acid. The ceramides were studied in mixtures with palmitoyloleoylphosphocholine (POPC) and/or palmitoylsphingomyelin (PSM), and in more complex bilayers also containing cholesterol. The trans-parinaric acid lifetimes showed that 12:1- and 14:1-PCer failed to increase the order of POPC bilayers, whereas 16:1-, 18:1-, and 20:1-PCer induced ordered- or gel-phase formation. Nevertheless, all of the analogs were able to thermally stabilize PSM, and a chain-length-dependent increase in the main phase transition temperature of equimolar PSM/Cer bilayers was revealed by differential scanning calorimetry. Similar thermal stabilization of PSM-rich domains by the ceramides was observed in POPC bilayers with a trans-parinaric acid-quenching assay. A cholestatrienol-quenching assay and sterol partitioning experiments showed that 18:1- and 20:1-PCer formed sterol-excluding gel phases with PSM, reducing the overall bilayer affinity of sterol. The effect of 16:1-PCer on sterol distribution was less dramatic, and no displacement of sterol from the PSM environment was observed with 12:1- and 14:1-PCer. The results are discussed in relation to other structural features that affect the bilayer properties of ceramides.
authors.affiliation: Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland. terhi.maula@abo.fi
authors.forename: Terhi
authors.initials: T
authors.lastname: Maula
authors.forename: Ibai
authors.initials: I
authors.lastname: Artetxe
authors.forename: Pia-Maria
authors.initials: PM
authors.lastname: Grandell
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
mesh_terms: D002151:Calorimetry; D002518:Ceramides / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D015394:Molecular Structure; D010713:Phosphatidylcholines / Q000737:chemistry; D013109:Sphingomyelins / Q000737:chemistry
chemical_list: D002518:Ceramides; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D013109:Sphingomyelins; C033171:palmitoylsphingomyelin; D002784:Cholesterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine