THe isoelectric point, pI, of an amino acid is the pH at which the predominant species in solution is the zwitterionic form of the amino acid and only small but equal concentrations of positively and negatively charged forms of the amino acid are present. It follows that at the isoelectric point, the average charge on the amino acid is zero. Required:
Show that pI= 1/2 (pKa1 + PKa2) for amino acids with side chains that are neither acidic nor basic (such as glycine and alanine).