The definition of the coordinate of CESS. The definition of coordinate of CESS vpara, and vperp for (a) an α helix and (b) a β strand are depicted. In the upper parts, an α helix and a β strand are depicted by a ribbon diagram, as well as by a ball-and-stick C
model. Black balls represents C
atoms of i-th SSSSE that starts from k-th residue. Gray balls represents . In the lower parts, and of the CESS are indicated by dashed arrows colored in blue and red, respectively. (c) An example of schematic representation of a β - α - β motif by a set of CESSs.