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  2. Importance of the sphingoid base length for the membrane properties of ceramides

Importance of the sphingoid base length for the membrane properties of ceramides

  • Biophys J. 2012 Nov 7;103(9):1870-9. doi: 10.1016/j.bpj.2012.09.018.
Terhi Maula 1 Ibai Artetxe Pia-Maria Grandell J Peter Slotte
Affiliations

Affiliation

  • 1 Biochemistry, Department of Biosciences, Åbo Akademi University, Turku, Finland. terhi.maula@abo.fi
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.

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