Figure 9.20 
Deoxygenated hemoglobin S. The interaction between valine 6 (blue) on a β chain of one hemoglobin molecule and a hydrophobic patch formed by phenylalanine 85 and leucine 88 (gray) on a β chain of another deoxygenated hemoglobin molecule leads to hemoglobin aggregation. The exposed valine 6 residues of other β chains participate in other such interactions in HbS fibers.
Deoxygenated hemoglobin S. The interaction between valine 6 (blue) on a β chain of one hemoglobin molecule and a hydrophobic patch formed by phenylalanine 85 and leucine 88 (gray) on a β chain of another deoxygenated hemoglobin molecule leads to hemoglobin aggregation. The exposed valine 6 residues of other β chains participate in other such interactions in HbS fibers.