4NS2:
reference: Charge-Disproportionation Symmetry Breaking Creates a Heterodimeric Myoglobin Complex with Enhanced Affinity and Rapid Intracomplex Electron Transfer., Trana EN, Nocek JM, Woude JV, Span I, Smith SM, Rosenzweig AC, Hoffman BM, J Am Chem Soc. 2016 Sep 28;138(38):12615-28. doi: 10.1021/jacs.6b07672. Epub 2016, Sep 20. PMID: 27646786

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