Isoelectric
What is Isoelectric?
The isoelectric point (pI) is the pH at which a molecule — particularly an amino acid, protein, or other amphoteric species — carries no net electrical charge. At the isoelectric point, the molecule has equal numbers of positive and negative charges and shows minimum solubility and electrophoretic mobility. For amino acids, the pI is calculated as the average of the pKa values flanking the zwitterionic form, and for proteins it depends on the sum of all ionizable side chains.
Key Facts
Frequently Asked Questions
The isoelectric point (pI) is the pH at which a molecule — particularly an amino acid, protein, or other amphoteric species — carries no net electrical charge. At the isoelectric point, the molecule has equal numbers of positive and negative charges and shows minimum solubility and electrophoretic mobility. For amino acids, the pI is calculated as the average of the pKa values flanking the zwitterionic form, and for proteins it depends on the sum of all ionizable side chains.