Deoxygenated hemoglobin S. The interaction between Val 6 (blue) on a β chain of one hemoglobin molecule and a hydrophobic patch formed by Phe 85 and Leu 88 (gray) on a β chain of another deoxygenated hemoglobin molecule leads to hemoglobin aggregation. The exposed Val 6 residues of other β chains participate in other such interactions in hemoglobin S fibers.
[Drawn from 2HBS.pdb.]