In strongly basic solutions all amino present as anions, in acidic solutions they are present as cations. At some intermediate Ph called isoelectric point(pl)the concentration of the dipolar ion is at its maximum and the concentrations of the anions and cations are equal H3CCHCO H --H3CCHCO, OH H3CCHCO2 H CH CH CH Cationic form Dipolar ion Anionic form (pKa1=23) (pKa2=97) As the acidity reaches ph2.3, one half of the cationic form will be converted to the dipolar ion. As the ph increase to23-9.7the predominant form will be the dipolar ion. When ph rise to 9.7, the dipolar ion will be half-converted to the anionic form. As pH approached to 14, the anionic form becomes predominant formIn strongly basic solutions all amino present as anions, in acidic solutions they are present as cations. At some intermediate Ph, called isoelectric point(pI) the concentration of the dipolar ion is at its maximum and the concentrations of the anions and cations are equal. H3 CCHCO2 H CH3 H3 CCHCO2 - CH3 H3 CCHCO2 - CH3 Cationic form (pKa1 = 2.3） Dipolar ion (pKa2 = 9.7） Anionic form OH - OH￾H + H+ As the acidity reaches pH 2.3, one half of the cationic form will be converted to the dipolar ion. As the pH increase to2.3- 9.7 the predominant form will be the dipolar ion. When pH rise to 9.7,the dipolar ion will be half-converted to the anionic form. As pH approached to 14,the anionic form becomes predominant form