9. Polyprotic Acid-Base Equilibria

Calculate the pI value for histidine. pK_a1 (carboxyl group) = 1.60, pK_a2 (ammonium group) = 9.28, pK_a3 (R-group) = 5.97. 

Calculate the pI value for gluatamic acid. pK_a1 (carboxyl group) = 2.16, pK_a2 (ammonium group) = 9.96, pK_a3 (R-group) = 4.30.