X-ray diffraction study of cholesterol-phosphatidylserine mixtures.

Phosphatidylserine-cholesterol mixtures at a molar ratio of 2:1 were investigated by X-ray diffraction. Phase separation of cholesterol independent of temperature was detected, indicating limited solubility of cholesterol in phosphatidylserine bilayers. The second phase present, the mixed phospholipid-cholesterol phase, continued to undergo melting as determined by changes with temperature in both the small angle scattering profile and in the acyl chain packing.