Contact maps and random errors. The contact map of the Asn102 mutant of trypsin (PDB code: 1trm chain A) is blurred with different types of random errors. Gray areas contain contacts (computed setting the threshold at 12 Å), white areas contain non-contact and black dots are errors. (a) The native map with 24753 residue pairs, of which 3595 are contacts, 21158 are non-contacts, and without random errors. (b) Err 5%. This map includes a number of random errors (1237) equal to 5% of total number of residue pairs. (c) Err-1 5%. In this map the total number of contacts is decreased by randomly substituting with non contacts (for a total of 179 non contacts corresponding to 5% of the original number of contacts). (d) Err-0 5%. In this map the total number of non contacts is decreased by randomly substituting with contacts (for a total of 1057 contacts corresponding to 5% of the original number of non contacts).