Dynamics of heme in hemoproteins: proton NMR study of myoglobin reconstituted with iron 3-ethyl-2-methylporphyrin

► Asymmetric 3-ethyl-2-methylporphyrin iron complex was inserted into apomyoglobin. ► Cyanide complexation to iron allowed to quench partially the heme reorientation. ► Two interconvertible forms were detected in solution by NMR.