Insights into Sphingolipid Miscibility: Separate Observation of Sphingomyelin and Ceramide N-Acyl Chain Melting
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| Authors: | Leung, SSW; Busto, JV; Keyvanloo, A; Goni, FM; Thewalt, J |
| Year: | 2012 |
| Journal: | Biophysical Journal 103: 2465-2474 Article Link (DOI) |
| 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 H-2 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 H-2 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. |
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