Easily calculate the Isoelectric Point (pI) of amino acids and small peptides. The pI is the pH at which a molecule has no net electrical charge, crucial for understanding protein behavior in solution, electrophoresis, and chromatography. Input relevant pKa values for a quick and accurate result.
Formula:
The Isoelectric Point (pI) is the pH at which a molecule (such as an amino acid or protein) carries no net electrical charge. For a molecule with two ionizable groups, the pI is simply the average of their two pKa values:
pI = (pKa1 + pKa2) / 2
For molecules with more than two ionizable groups (like amino acids with ionizable side chains), the pI is calculated by averaging the two pKa values that define the neutral (zwitterionic) species. These are the pKa values of the groups that protonate and deprotonate across the neutral charge state.