Glutamic acid H2N−CH(CH2CH2COOH)−COOHN has pKa1(α−COOH)=2.2,pKa2(R group COOH)=4.3. The isoelectric point of glutamic acid is
H3+N−CH|CH2CH2COOHCationic form−COOHOn neutralisation⟶1st ionizationH3+N−CH|CH2CH2COOH−COO−⟶2nd ionizationH3+N−CH|CH2CH2COO−−COO−
Isoelectric poin (pI)=pKa1+pKa32
2.2+4.32=3.25