Complementarity plot

The complementarity plot (CP) is a graphical tool for structural validation of atomic models for both folded globular proteins and protein-protein interfaces.

[7] Validation of three dimensional protein crystal structures are traditionally based on a multitude of parameters ranging from (i) the distribution of residues in the Ramachandran plot,[8][9] (ii) deviations from ideality,[10][11] for bond lengths and angles, (iii) atomic short contacts (steric clash scores),[12] (iv) the distribution of the side-chain conformers (rotamers)[13] and, (v) hydrogen bonding parameters.

CP detects both local errors in atomic coordinates and also correctly matches an amino acid sequence to its native three dimensional fold situated amid decoys.

Disharmony (misfit) in these conjugated parameters may arise due to a plethora of errors coming from bond angles or torsions from effectively the whole folded polypeptide chain.

Consequences of such small angular errors are not restricted locally, resulting in geometric and electrostatic misfit of interior residues throughout the fold, potentially detectable by the CPs.

Sc,[17] EC[18] are shape and electrostatic complementarities computed for 'interacting protein-protein surfaces' originally proposed by Peter Colman and co-workers in the 1990s.