ALPHA-TOCOPHEROL INTERACTS WITH NATURAL MICELLE-FORMING SINGLE-CHAIN PHOSPHOLIPIDS STABILIZING THE BILAYER PHASE

The effect of the association of α-tocopherol (vitamin E) with single chain or very asymmetric phospholipids has been studied by 31P nuclear magnetic resonance, Fourier transform infrared spectroscopy, and light microscopy. Our results demonstrate that α-tocopherol stabilizes and forms bilayer structures in systems composed of either 1-palmitoyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 1-O-hexadecyl-sn-glycero-3-phosphocholine, or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1-palmitoyl-sn-glycero-3-p hosphocholine, whereas in the absence of α-tocopherol all these systems produce micellar structures. The free hydroxyl group of α-tocopherol is shown to be important in stabilizing the bilayer structure by comparing the effects produced by an analog of α-tocopherol, α-tocopheryl acetate, which has the hydroxyl group blocked by an acetyl group. It is suggested that the complementary shapes of α-tocopherol and the asymmetric phospholipids may be the reason for the stabilization of the bilayer structure. © 1993 Academic Press, Inc.