Protein alpha helix structure, diagram. The alpha helix is one of the secondary structures of proteins (along with beta sheets). The alpha helix is sometimes called the Pauling-Corey-Branson alpha helix after Linus Pauling, Robert Corey, and Herman Branson, who published details of this structure in 1951. The alpha helix is a repeated protein structural element. This view shows the hydrogen bonds (dotted lines) between the carboxyl (C=O) and amine (NH) groups. The atoms in this molecular model are colour-coded: carbon (brown), oxygen (red), nitrogen (light blue), and hydrogen (purple). The helical coil distance is labelled as 5.4 angstroms.