4M4A:
reference: Degradation of human hemoglobin by organic C-nitroso compounds., Yi J, Ye G, Thomas LM, Richter-Addo GB, Chem Commun (Camb). 2013 Dec 11;49(95):11179-81. doi: 10.1039/c3cc46174b. Epub, 2013 Oct 23. PMID: 24149619

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