β-peptides consist of beta amino acids , which have an amino group in the β-position. Because the backbones of β-peptides are longer than those of peptides that consist of α-amino acids, β-peptides form a secondary structure different from that of normal peptides. In addition to the interest in creating new structures, the possibility of new functions created by the new structures has been enhancing the interest in β-peptides recently.
Although the structure of peptide depends on the chemical structure of the amino acid, many kinds of β-peptides form helix structures. This feature is due to the local conformation of the β-amino acid; alkyl substituents at position α and β favor a gauche conformation about the bond between the α-carbon and β-carbon. This also affects the thermodynamic stability of the structure. Generally speaking, β-peptide forms a more stable helix than α-peptide does.
Many types of helix structures consisting of β-peptides have been reported. These conformation types are distinguished by the number of atoms in the hydrogen-bonded ring; 8-helix, 10-helix, 12-helix, 14-helix, and 10/12-helix have been reported.
There are great possibilities for β-peptides in biology. It was found that β-peptides are stable against proteolytic degradation in vitro and in vivo, an important advantage over natural peptides.