Loop sequences and sources for all test cases.

For statistics Ncontact, Nout, NSC, and NHB, residues with sequence positions within two residues of each loop residue were excluded from the calculation; only non-hydrogen atoms were considered.aAverage number of residues that make at least one atom-atom contact (distance bAvg. number of residues outside the loop that make an atom-atom contact (dist. cAvg. number of residues that make an atom-atom contact (dist. dAvg. number of hydrogen bonds per residue, defined as donor/acceptor pairs with distance less than 3.2 Å.eTest included two crystallographic neighbors that interact with loop [21], [22].fLoop with irregular structure that remains rigid upon binding to inhibitors or protein partners; see cited references.gUnpublished 275-residue protein crystal structure from W. Weis and colleagues (see Figs. 5A–D).