The isoelectric point (pI, or sometimes abbreviated to IEP) is the pH at which a particular molecule or surface carries no net electrical charge.
The Isoelectric Point Plugin calculates the gross charge distribution of a molecule as a function of pH. The result appears in a separate window, containing the molecule with the pI and (if enabled) the pH:charge plot. Hovering the mouse over the points of the curve, the pH:charge value pairs appear.
Fig. 1 Isoelectric Point Plugin result window
The Isoelectric Point Options window offers the following options to set:
Fig. 2 Isoelectric Point Options window