1GZX:
reference: Crystal structure of T state haemoglobin with oxygen bound at all four haems., Paoli M, Liddington R, Tame J, Wilkinson A, Dodson G, J Mol Biol 1996 Mar 8;256(4):775-92. PMID: 8642597

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