The two-chain protein interface in our definition was composed of interacting residues and nearby residues, respectively. The interfaced residues was picked up first. If the distance of any two atoms between residues is less than their sum of van der Waals radii plus 0.5 Angstrom, both residues were registered as the interfaced residues. When assigned interface residues was less than 10 residues, an arbitrary but reasonable number to reflect the minimum requirement of contact, the interface was considered as a result of crystal packing force. Therefore, it would not be considered further. To enable illuminating the types of architectures at the interface, residues whose alpha carbon atom is within a distance of 6.0 Angstrom from an alpha carbon atom of previous assigned interface residues, are included and named nearby residue. The 6.0 Angstrom selected from trial and error is very close to the lowest distance to include residues not involving in interface but essential for demonstrating the scaffold of the interface.