SPHINGOMYELIN-LECITHIN BILAYERS AND THEIR INTERACTION WITH CHOLESTEROL

Utilizing X-ray diffraction and differential scanning calorimetry (DSC), we have studied (1) the structure and thermotropic properties of hydrated 7V-palmitoyl-sphingomyelin, (2) the interaction of N-palmitoylsphingo-myelin with dimyristoyllecithin, and (3) the interaction of cholesterol with N-palmitoylsphingomyelin and dimyristoyllecithin, both individually and in a 50:50 (mol/mol) mixture. N-Palmitoylsphingomyelin forms bilayers which undergo a thermotropic order-disorder (gel-liquid crystalline) transition at 40.5 °C (AH=5.8 kcal/mol). The bilayer repeat distance is 66.8 υ at 10 °C and 61.6 υ at 50 °C. TV-Pal-mitoylsphingomyelin exhibits miscibility with dimyristoyllecithin in both the gel and liquid-crystalline phases, and no lateral phase separation occurs. Scanning calorimetry indicates that interaction with cholesterol is similar for both iV-pal-mitoylsphingomyelin and dimyristoyllecithin and that in a 50:50 (mol/mol) mixture cholesterol shows no preferential affinity for either phospholipid. © 1979, American Chemical Society. All rights reserved.