Blood, deoxygenation anemia

When HbS is deoxygenated it tends to "crystallize" in red blood cells, which contain 33% by weight hemoglobin. The crystallization (actually gel formation) distorts the cells into a sickle shape and these distorted corpuscles are easily destroyed, leading to anemia. The introduction of the hydrophobic valine residue in Hb S at position 6 near the end of the molecule helps form a new bonding domain by which the hemoglobin tetramers associate to form long semicrystalline microfilamentous arrays. 3 6 s... 

Fig. 5. At the left, molecules of normal hemoglobin or of oxygenated sickle-cell-anemia hemoglobin are shown, with random orientations, and at about the average distance apart characteristic of red-cell contents. At the right long strings of molecules of deoxygenated sickle-cell-anemia hemoglobin are shown, assuming the parallel orientation characteristic of the nematic liquid crystals that presumably form within the red cells in the venous blood of patients with sickle-cell anemia, and twist the red cells into the abnormal shape characteristic of the disease.

FBj. 3. Sickled erythrocytes in oxygen-depleted whole blood from a patient with sickle-cell anemia, demonstrating the similarities in shape to tactoids formed in stroma-free solutions of their deoxygenated hemoglobin. Phase photomiaography, X 375. From John W. Harris, Proc. Soc. Bxptl. Biol, and Med. 75, 197 (1950). 

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