Fig. 4.

Left: extended models for the nitrite adducts of hemoglobin, taking into account sterical and hydrogen bonding conditions at the distal pocket around the nitrite. Right: views of the heme, perpendicular to the macrocyclic plane from a direction trans to the proximal histidine, obtained from crystal structures of Hb in the deoxy and in the ferric nitrite-bound forms (only the atoms included in our computational models are shown). These structures were employed as starting points in our calculations. Color code: carbon – gray, hydrogen – white, iron – green, porphyrin nitrogen – blue. The nitrite is shown in orange.