1IRC:
reference: Replacement of the proximal ligand of sperm whale myoglobin with free imidazole in the mutant His-93-->Gly., Barrick D, Biochemistry. 1994 May 31;33(21):6546-54. PMID: 8204590

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