Residue propensities for protein-protein interfaces. The propensity of each of the 20 canonical residues for the four different structural environments suggests a highly environment-dependent distribution. Grey bars indicate the overall observed frequency across all environments (B
in Equation 3). Coloured bars indicate the environment dependent residue frequency (E
in Equation 4). Coloured bars higher than their respective gray bars indicate the normalized environment-dependent propensity (R
in Equation 5) is greater than 1. Residues are ordered by decreasing hydrophobicity from left to right. Inset pie chart indicates the underlying proportion of each of the four residue environments.