stereographical projection map and Ramachandran map. (Color online) Top: The stereographically projected Frenet frame map of backbone Cα atoms, with major secondary structures identified. Also shown is the direction of the Frenet frame normal vector n; the vector t corresponds to the red circle at the center, and it points away from the viewer. The map is constructed using all PDB structures that have been measured with better than 2.0 Å resolution. Bottom: Standard Ramachandran map, constructed using our 1.0 Å resolution PDB subset. Major secondary structures have been identified.