4IT2:
reference: Porphyrin-Substituted H-NOX Proteins as High-Relaxivity MRI Contrast Agents., Winter MB, Klemm PJ, Phillips-Piro CM, Raymond KN, Marletta MA, Inorg Chem. 2013 Feb 8. PMID: 23394479

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