Abstract
Hemoglobin (Hb)-based oxygen carriers are the potential source of blood substitutes during emergency medical situations. To make these oxygen carriers practical and commercially viable blood substitutes, one needs to design the Hb molecule to fulfill the three essential requirements. First, the designed Hbs should deliver oxygen efficiently, i.e., they should combine with and unload oxygen cooperatively like human normal adult hemoglobin (HbA) inside red blood cells. Second, in the extra-cellular environment, because of the absence of allosteric effectors, such as 2,3-diphosphoglycerate (2,3-DPG), which serve to lower the oxygen affinity of Hb within the red blood cell, it is essential to have Hbs with low oxygen affinity. Third, the designed Hbs should be stable against the oxidation of the heme iron atom from the ferrous to the ferric state and should not dissociate readily into the dimers of Hb. Several naturally occurring mutant Hbs, such as Hb Kansas and Hb Titusville, have decreased cooperativity and have a strong tendency to dissociate into dimers upon oxygenation. Thus, this type of Hb is not suitable as an acellular oxygen carrier.
Published Version
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