<prompt> In hemoglobin, the innate affinity of heme for carbon monoxide is diminished by the presence of :His F8His E7Gly B6Thr C4  <response>: The heme has high affinity for carbon monoxide about 25000 more than for 02. But when heme molecule is associated with Histidine E 7 as occurs in myoglobin, its affinity for CO is drastically reduced because His E 7 creates a hindered environment for CO by disturbing the orientation of atoms in heme molecules. 