text: Schematic representation of the definition of the side- | Open-i
  f2-6_27: Schematic representation of the definition of the side-chain crick angle.
  Mentions: The crick angle is defined in TWISTER for two helices (A and B) in a coiled-coil by the average of the angles COAXA and COBXB, where OA is a point on the central axis of helix A, C is the center of the coiled-coil defined by (OA+OB)/2, and XA represents the position of Cα in helix A at which the crick angle is defined (Fig. 2). However, the original definition, based on the position of Cα, is not necessarily appropriate for rigorously defining the direction of a side-chain forming core packing in coiled-coil. To solve this problem, we defined the side-chain crick angle by changing the definition of XA to the center of mass of nonhydrogen atoms in the side-chain projected onto the plane defined by OAOB and an axis perpendicular to the coiled-coil axis.