The isoelectric point (pI) is the pH at which a particular molecule carries no net electrical charge. The net charge on the molecule is affected by the pH of its surrounding environment and can become more positive or negative due to the gain or loss of protons, respectively. A net charge of 0 may result in protein Aggregation. It is important to note that the calculation of the pI for a protein purely based on its amino acid sequence is often imprecise, since protein folding, modification and also labeling can influence the pI.
Isoelectric point is one of the key parameters that help profile biologics in addition to stability, aggregation, and particle sizing.