3MLH:
reference: The Receptor-Binding Domain of Influenza Virus Hemagglutinin Produced in Escherichia coli Folds into its Native, Immunogenic Structure., Dubois RM, Aguilar-Yanez JM, Mendoza-Ochoa GI, Oropeza-Almazan Y, Schultz-Cherry S, Alvarez MM, White SW, Russell CJ, J Virol. 2010 Nov 10. PMID: 21068239

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