Fig. 4

C _α stereographical projection map and folding index. (Color online) a The stereographically projected Frenet frame map of backbone C α atoms, with major secondary structures identified. Also shown is the directions of the Frenet frame normal vector n; the vector t points upwards and colour coding corresponds to the number of PDB entries with red large, blue small and white none. b An example of a loop (kink) trajectory, starting (a) and ending (e) in α-helical position