Peptide libraries

A library of synthetic peptides, comprising linear and cyclic peptides,

• wherein the cyclic peptides have different loop lengths, and
• wherein some of the cyclic peptides have single loops and other cyclic peptides have two or more loops, and
• wherein the synthetic peptides of said library comprise a controlled ratio of cysteines at certain positions,
• wherein the cyclic peptides are formed by one or more covalent bonds,
• wherein said covalent bond is a disulfide bond formed by two cysteine residues,
• wherein each member of the library comprises an amino acid sequence
• Cmix-(X)m-(Amix)n,
• wherein
• a) Cmix is a mixture of 50% cysteine and an equal mixture of the remaining natural occurring amino acids,
• b) X are each an equal mixture of the natural occurring amino acids, excluding cysteine,
• c) Amix are each a mixture of 5-50% cysteine and an equal mixture of the remaining natural occurring amino acids, and
• d) m and n are both, and independently from each other, 3-20.