assuming that in the reduced p450 as well as in its co-complex the protein-derived ligand is mercaptide ( rs- ) the differences can be explained by the existence of two electronic transitions in the soret region : the common for hemoproteins pi -- -- pi porphyrin transition and sulfur to porphyrin charge-transfer transition , p+ ( sp ) -- -- eg ( pi ) .
C0010762
p450
C0018974
hemoproteins