To calculate the isoelectric point of amino acids having otherionizable functional groups, we must also take into account the
pKa
of the additional functional group in the side chain.
| For an acidic amino acid (one with an additional acidic OHgroup): | | | For a basic amino acid (one with an additional basic NHgroup): |
|   | | | |
pI =pKa (α -COOH) +pKa (side COOH) | | 2 |
| | | pI =pKa (α -NH3+) +pKa (side NH) | | 2 |
|
Indicate which
pKa
values must be used to calculate the pI of thefollowing amino acids: [1] aspartic acid; [2] arginine; [3] lysine.Be sure to answer all parts.
Amino Acid | pKa (α group) | pKa (side chain group) |
| aspartic acid | | |
| arginine | | |
| lysine | | |
