Isoelectric focusing

Isoelectric focusing electrophoretically separates proteins on the basis of their associative content of negatively and positively charged collections. When a protein is at its pI its net charge is zero and thus it will not move in an electric area.  In  isoelectric  focusing,  a  polyacrylamide   gel  is  used  that  has large pores so as not to impede  protein  migration  and contains  a mixture  of polyampholytes small multicharged  polymers that have several pI values. If an electric ?eld is applied to the gel the polyampholytes produce and migrate a pH gradient.  To divide proteins through isoelectric focusing they are electrophoresed by such a gel. Every protein will migrate by the gel until it reaches a position at that the pH is equal to its pI which is shown in figure. If a protein diffuses away from this position its net charge will modify as it moves into a region of another pH and the resulting electrophoretic concentrate will move it back to its isoelectric position. In this pathway every protein is concentrated into a narrow band as thin as 0.01 pH unit about its polyacrylamide.