title: Insights into sphingolipid miscibility: separate observation of sphingomyelin and ceramide N-acyl chain melting.
abstract: Ceramide produced from sphingomyelin in the plasma membrane is purported to affect signaling through changes in the membrane's physical properties. Thermal behavior of N-palmitoyl sphingomyelin (PSM) and N-palmitoyl ceramide (PCer) mixtures in excess water has been monitored by ²H NMR spectroscopy and compared to differential scanning calorimetry (DSC) data. The alternate use of either perdeuterated or proton-based N-acyl chain PSM and PCer in our ²H NMR studies has allowed the separate observation of gel-fluid transitions in each lipid in the presence of the other one, and this in turn has provided direct information on the lipids' miscibility over a wide temperature range. The results provide further evidence of the stabilization of the PSM gel state by PCer. Moreover, overlapping NMR and DSC data reveal that the DSC-signals parallel the melting of the major component (PSM) except at intermediate (20 and 30 mol %) fractions of PCer. In such cases, the DSC endotherm reports on the presumably highly cooperative melting of PCer. Up to at least 50 mol % PCer, PSM and PCer mix ideally in the liquid crystalline phase; in the gel phase, PCer becomes incorporated into PSM:PCer membranes with no evidence of pure solid PCer.
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada.
authors.forename: Sherry S W
authors.initials: SS
authors.lastname: Leung
authors.forename: Jon V
authors.initials: JV
authors.lastname: Busto
authors.forename: Amir
authors.initials: A
authors.lastname: Keyvanloo
authors.forename: Félix M
authors.initials: FM
authors.lastname: Goñi
authors.forename: Jenifer
authors.initials: J
authors.lastname: Thewalt
mesh_terms: D002518:Ceramides / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry; D050866:Liquid Crystals / Q000737:chemistry; D044367:Phase Transition; D013109:Sphingomyelins / Q000737:chemistry*; D013696:Temperature
chemical_list: D002518:Ceramides; D013109:Sphingomyelins; C033171:palmitoylsphingomyelin; C097760:N-palmitoylsphingosine; D002784:Cholesterol