What is the definition of the "isoelectric point" (pI) of a protein?
The isoelectric point (pI) of a protein is the pH at which a zwitterionic molecule does not migrate in an electric field, because its NET CHARGE IS ZERO.
That's a definition that is easy to find but somewhat more difficult to understand. ...
The solution contains an "official" definition of pI (isoelectric point), as well as an explanation of a more practical definition.