3NVY:
reference: X-ray Crystal Structure of a Xanthine Oxidase Complex with the Flavonoid Inhibitor Quercetin., Cao H, Pauff JM, Hille R, J Nat Prod. 2014 Jul 25;77(7):1693-9. doi: 10.1021/np500320g. Epub 2014 Jul 1. PMID: 25060641

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