The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of interactions between subunits.

Hydrophobic

Explanation:

The glutamic acid in the 6th position of beta chain of HbA is changed to valine in HbS. The substitution of hydrophilic glutamic acid by hydrophobic valine causes a sickness on the surface of the molecule.

This single nucleotide change polymerises hemoglobin molecules in the red blood cell.

So the hydrophobic nature of valine causes the aggregation of hemoglobin protein.

diaria maybe go see a doctor about that