Fig. 1.

Identification of residue points for use in the four-body contacts. The four black points represent the side chain geometric centers of sequential residues i, i + 1, i + 2, and i + 3. The red point is the geometric center of the four black points which is chosen as the center of the interacting group. The six planes, defined by each of the six combinations of pairs of black points and the central red point, fully subdivide the space surrounding the red point into four tetrahedra. The blue points represent other residues in close proximity to the red point, within the interaction range of 8.0 Å from it. An example of a set of four contacting residues used for potential extraction is shown by the four residues in boxes