1C2D:
reference: Design of potent selective zinc-mediated serine protease inhibitors., Katz BA, Clark JM, Finer-Moore JS, Jenkins TE, Johnson CR, Ross MJ, Luong C, Moore WR, Stroud RM, Nature 1998 Feb 5;391(6667):608-12. PMID: 9468142

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