Plot of mean sequence entropies 〈s 〉core and 〈s 〉rim of the core and rim regions in the interfaces in homodimers (a), protein-protein complexes (b), and crystal contacts of monomeric proteins (c). In a few cases (especially, when the protein family contains only a few members), 〈s 〉core and 〈s 〉rim are both zero. The numbers of points lying on the origin in the three plots are 3, 0, and 6, respectively. In b, ○ indicates antigen-antibody complexes.