PEPTIDE SELF-ASSEMBLY IN PHOSPHOLIPID-BILAYER MEMBRANE

A series of peptides has been synthesized and studied on the conformation, location, molecular orientation, and self-association in phospholipid bilayer membrane. Hydrophobic peptides tend to associate in the membrane of a crystalline state irrespective of the peptide chain length. Hydrophobic alpha-helical peptides of a chain length corresponding to the membrane thickness formed an aggregate in the membrane of a liquid-crystalline state with the helix axis oriented perpendicularly to the membrane surface. A hydrophobic octapeptide also took a perpendicular orientation predominantly in the membrane by connecting a hydrophilic group, lactose or crown ether, at the C-terminal of the peptide, which provides an amphiphilic property in the primary structure. The peptides taking transmembrane orientation formed a voltage-dependent ion channel. On the other hand, alpha-helical peptides with secondary amphiphilicity were incorporated at the membrane surface with the helix axis oriented parallel to the membrane. Some peptides with net charge associated at the membrane surface, though the size of aggregate was not large.