. The pI is called . The rule of calculating pI of an amino acid is that first, write the dissociation equation from fully protonated form to fully deprotonated form, label the charge of each form; second, identify the zwitterionic form (zero charge) and find the closest pKs (left and right side in the dissociation equation); third, average these two pKs. Write the dissociation equations for amino acids, glutamate, histidine, and calculate their pIs.

The isoelectric point is that the pH at which the compound is in an electronically neutral form.

For diss equations, please find them in the enclosed file.

The pIs of 2 amino acids:

Explanation:

Formula for the pI calculation: pI = (pKa1 + pKa2)/2

Given 3 pKa :

Use the lower 2  pKas (corresponding with 2 -COOH groups)

pKa1 = 2,19; pKa2 = 4,25; so pI = 3,2

Use the higher 2 pKas ( -COOH group and -NH= group)

pKa1 = 6; pKa2 = 9,17; so pI = 7,6

"the periodic table is arranged in order of atomic number."