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. This secondary structure is also sometimes called a classic Pauling–Corey–Branson alpha helix. The name3.6₁₃-helix is also used for this type of helix, denoting the number of residues per helical turn, and 13 atoms being involved in the ring formed by the hydrogen bond. Among types of local structure in proteins, the α-helix is the most regular and the most predictable from sequence, as well as the most prevalent.

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 -47.0

Download the .pdb file here.