1X9F:
reference: Crystal structure of the hemoglobin dodecamer from Lumbricus erythrocruorin: allosteric core of giant annelid respiratory complexes., Strand K, Knapp JE, Bhyravbhatla B, Royer WE Jr, J Mol Biol 2004 Nov 12;344(1):119-34. PMID: 15504406

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