Peptides containing N-substituted L-amino acids for preventing .beta.-strand association

DETAILED DESCRIPTION The invention claimed is: 1.
A peptide comprising a peptide, wherein: (a) said peptide comprises a .
beta.
-strand-forming section, said section consisting of four to sixteen consecutive .
alpha.
-L-amino acid residues and encompassing at least 50% of the length of said peptide, none of the .
alpha.
-L-amino acid residues within the .
beta.
-strand-forming section being proline, except at very ends of the .
beta.
-strand-forming section; (b) each of the consecutive .
alpha.
-L-amino acid residues in the .
beta.
-strand-forming section has a side chain; (c) said .
beta.
-strand-forming section forms a .
beta.
-strand having a peptide backbone which takes on the form of an extended ribbon having two edges, a first edge which associates with a target .
beta.
-strand formed by a separate peptide-containing molecule and a second edge, such that the NH and CO components of successive .
alpha.
-L-amino acid residues lie along the first edge and the second edge of the ribbon, the first edge and second edge corresponding to two opposite edges of the plane of the ribbon, and the side chains of the consecutive .
alpha.
-L-amino acid residues being alternatively above or below the plane of the ribbon; (d) at least one of the N.
alpha.
-atoms within the peptide backbone of the .
beta.
-strand is N.
alpha.
-substituted with an N.
alpha.
-substituent, such that one or more N.
alpha.
-substituent lie along only the second edge and sterically hinder the association of the second edge with another .
beta.
-strand; and (e) the first edge remains free of N.
alpha.
-substituents, and is not prevented from associating with the target .
beta.
-strand formed by a separate peptide-containing molecule.
2.
The peptide according to claim 1, wherein, when there are two or more successive N.
alpha.
-substituted amino acid residues, no two successive N.
alpha.
-substituted amino acid residues in the .
beta.
-strand-forming section are separated by more than 3 consecutive N.
alpha.
-unsubstituted amino acid residues.
3.
The peptide according to claim 1 wherein, when there are two or more successive N