And that's exactly why this fe atom will be found slightly below the protoporphine plane, as shown in the following diagram. So in deoxy hemoglobin or deoxy myoglobin. When the protein is not bound to the oxygen, the iron atom remains unbound to oxygen. And in this case, the fe metal atom is simply too large. It has too large of an electron density around that proton nucleus for that entire metal atom to actually fit snugly in the center of that protoporphine. And so what that means is this fe atom will be found slightly below.