Figure 1.
Delaunay and Voronoi descriptions of a protein–protein interface. Atoms are drawn as balls centered in a1 for the red molecule, and a2, a3, and a4 for the blue molecule. The ball radii are group radii augmented of the water probe radius. (A) Condition α: Delaunay edges are drawn in blue between the blue atoms and in green between blue and red atoms; the green edge between A1 and A4 is dashed to indicate that it is not part of the alpha-complex for α = 0. Thus, the interface between the red and the blue molecules comprises only the two Voronoi facets drawn in a thick green line. (B) Condition β: The dashed circle represents a ball orthogonal to the balls representing atoms A1, A3, and A4. Its radius being m, the facet between A1 and A4 (thick green line) will be accepted or discarded depending on the ratio m/r, where r is the radius of A1.