What is the isoelectric point?

The isoelectric point (pI) is the pH at which a molecule carries no net electrical charge. This means that the molecule has an equal number of positively and negatively charged groups, resulting in a net charge of zero.

The pI of a molecule is determined by the presence of acidic and basic groups within the molecule. At pH values below the pI, the molecule will have a net positive charge (due to more acidic groups being protonated) and at pH values above the pI, the molecule will have a net negative charge (due to more basic groups being deprotonated).

The pI is important in various biochemical and biotechnological applications, such as determining the optimal conditions for separating proteins by isoelectric focusing or predicting the solubility and stability of a protein under different pH conditions.

Calculating the pI of a molecule can be done using various methods, including experimental techniques such as isoelectric focusing or theoretical calculations based on the pKa values of the acidic and basic groups present in the molecule.