Figure 5.

Plots of the distances of His 64 N_ɛH (solid line) and His 64 C_δH (broken line) from the heme iron atom vs. (A) the dihedral angle around the C_α–C_β (χ₁) rotational bond, and (B) the dihedral angle around the C_β–C_γ (χ₂) rotational bond. The distances between the targeted protons and the iron atom were calculated by the program MOLMOL using the neutron data of Cheng and Schoenborn (1990) (PDB:2mb5). Arrows in the figure indicate the dihedral angles of MbCO in the crystal at atmospheric pressure (PDB:2mb5).