4A4A:
reference: Structural analysis of a bacterial exo-alpha-D-N-acetylglucosaminidase in complex with an unusual disaccharide found in class III mucin., Ficko-Blean E, Boraston AB, Glycobiology. 2012 May;22(5):590-5. doi: 10.1093/glycob/cwr165. Epub 2011 Nov 16. PMID: 22090394

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