1U9W:
reference: Novel purine nitrile derived inhibitors of the cysteine protease cathepsin K., Altmann E, Cowan-Jacob SW, Missbach M, J Med Chem 2004 Nov 18;47(24):5833-6. PMID: 15537340

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).