2A3C:
reference: Methylxanthine drugs are chitinase inhibitors: investigation of inhibition and binding modes., Rao FV, Andersen OA, Vora KA, Demartino JA, van Aalten DM, Chem Biol. 2005 Sep;12(9):973-80. PMID: 16183021

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