beta-Carotene or chlorophyll alpha incorporated in lecithin liposomes. Analysis by ultracentrifugation.

Ultracentrifugal analyses show that β-carotene and chlorophyll a are incorporated into the membranes of lecithin liposomes without any increase of the particle size. The sedimentation coefficient and particle weight of the liposomes increase up to a maximum value (4.3 S and 3.1 × 10⁶ respectively) for a molar ratio of pigment to lecithin of about 0.02, due to an increasing number of lecithin molecules per particle. The pigments lower the average surface area of the polar heads of lecithin down to a minimum of 79 A²/molecule. When the molar ratio of chlorophyll a to lecithin is above 0.02, the characteristics of the vesicles do not change, indicating a different type of incorporation of the chlorophyll molecules in the membranes.