The amphipathic alpha-helix concept. Application to the de novo design of ideally amphipathic Leu, Lys peptides with hemolytic activity higher than that of melittin.

An original series of 12- to 22-residue-long peptides was developed, they are only constituted by apolar Leu and charged Lys residues periodically located in the sequence in order to general ideal highly amphipathic alpha-helices. By circular dichroism, the peptides are proven to be mainly alpha-helical in organic and aqueous solvents and in the presence of lipids. The peptides are highly hemolytic, their activity varies according to the peptide length. The 15-, 20-, and 22-residue-long-peptides have LD50 approximately 5 x 10(-8) M for 10(7) erythrocytes, i.e. they are 5-10 times more active than melittin, and are indeed several orders of magnitude more active than magainin or mastoparan.