AN410 Measuring the isoelectric point pf peptides by potentiometric titration

The isoelectric point (pI) is the pH at which biological amphoteric molecules such as peptides and proteins carry no net electrical charge. Biopharmaceutical drug formulations that are intended for subcutaneous injection are often prepared at about pH 4 to enhance shelf life but when they are injected into the body the pH swiftly moves to 7.4. If the isoelectric point is between these pH values, there is increased risk of precipitation and aggregation after injection, which could diminish bioavailability.