Alteration of lipid-phase behavior in multiple sclerosis myelin revealed by wide-angle x-ray diffraction.

Wide-angle x-ray diffraction studies revealed that the lipid-phase transition temperature of multiple sclerosis (MS) myelin was about 20 degrees C lower than that of normal myelin, indicating differences in the physical organization of the bilayer. The transition temperature of liposomes prepared from total lipid extracts of normal myelin was 12 degrees C lower than that for corresponding intact myelin, demonstrating that the protein of normal myelin had a substantial ordering effect on the lipid bilayer. The transition temperature for liposomes of MS myelin lipid was essentially similar to that for isolated MS myelin. Because the protein/phospholipid ratio was higher in MS myelin, and no difference in degree of fatty acid saturation was observed, the inability of MS myelin protein to organize the lipid reflects a qualitative difference in the proteins.