Protein Structure Quality Score (PSQS)

PSQS is an energy-like measure of the quality of protein structure. It is calculated based on the statistical potentials of mean force describing interactions between residue pairs and between single residues and solvent. Three sets of statistical potentials have been obtained from the statistics calculated for representative set of 1836 proteins containing all domain folds available in the SCOP database:

Local potential - describes local geometry propensities of polypeptide chain. It is a function of residue types of residues i-1, i and i+1.

Burial potential - describes the tendency of hydrophobic residues to concentrate in the protein core and the tendency of hydrophilic residues to concentrate on the protein surface.

Contact potential - describes the likelihood of different residue pairs to be in close contact.