The pI for amino acids (the pH of the isoelectric point) is exactly half-way between the pKa values of the two functional groups. Note that the aspartame has the carboxylic acid functionality of phenylalnine converted to an ester and the carboxylic acid of aspartic acid and linked as an amide to the amine group of phenylalanine. This leaves the aspartic acid amine group and the side chain carboxylic acid functional group of aspartic acid. Therefore aspartame will have an isoelectric point at a pH between the pKa values of these functional groups. Find the values for these two groups of aspartic acid and calculate a predicted pI value for aspartame.