3AQ9:
reference: A hydrogen-bonding network formed by the B10-E7-E11 residues of a truncated hemoglobin from Tetrahymena pyriformis is critical for stability of bound oxygen and nitric oxide detoxification., Igarashi J, Kobayashi K, Matsuoka A, J Biol Inorg Chem. 2011 Feb 5. PMID: 21298303

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