Structured peptide scaffold for displaying turn libraries on phage

A cyclic peptide scaffold for presenting a β-turn hairpin structure, said cyclic peptide scaffold comprising an amino acid sequence C1-A1-A2-(A3)n-A4-A5-C2 -(SEQ ID NO:1), wherein

• C1 and C2 are cysteines;
• A1, A2, A3, A4, and A5 are naturally occurring L-amino acids;
• the N′-terminus of the scaffold is optionally protected with an amino protecting group;
• the C′-terminus of the scaffold is optionally protected with a carboxy protecting group;
• A1 and A5 are selected from the group consisting of amino acids W, Y, F, H, I, V and T;
• A2 and A4 are selected from the group consisting of amino acids W, Y, F, L, M, I, and V;
• A3 is any naturally occurring L-amino acid and n is an integer that is 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12;
• and
• C1 and C2 are joined together by a disulfide bond thereby forming a cyclic peptide.