An alpha helix is a commonly-found protein secondary structure. It is a right-handed coil in which every backbone N-H group donates a hydrogen bond to the C=O group of the amino acid four residues earlier. In the less common pi helix, the bonding occurs at the amino acid five residues earlier resulting in a wider helical conformation.

This helix consists of 20 amino acid peptides of poly-L-alanine, and were produced using the peptide builder in Chimera. Phi angle is set at -57.0, and psi angle is set at -70.0

Download the .pdb file here.