Fig. 3

Best-fit synthetic structural exemplars with example clusters. Best-fit synthetic structural exemplars for the sets of all loop structures at the N-terminus (a, b) and C-terminus (c, d) of alpha helices, generated by 3D backbone clustering. At each terminus, a lower resolution plot that covers 3 loop residues with 16 exemplars (3R/16C) is shown at left, along with a higher resolution plot that extends coverage to 4 loop residues using 32 exemplars (4R/32C) at right. The width of each exemplar is proportional to the number of loop structures in its corresponding cluster. The synthetic exemplars capture the typical backbone geometries associated with abundant loop structures. At the N-terminus, these geometries are colour-coded in red for the “capping box”, purple for the “big box”, orange for the “expanded box”, yellow for beta-turns towards (+x), and blue for beta-turns towards (−x). At the C-terminus, the colours are red for the Schellman loop, yellow for beta-turns, and orange for combined Schellman loops and beta-turns. Samples of the clusters of actual loop structures that are associated with the exemplars are given below each exemplar plot using the same colour coding