Point at which proteins stop moving on a gel when they get a netcharge of zero.
pI = pKa(+1 charge) + pKa(-1 Charge)
-Average the pK values from +1 to -1 charge.
-Proteins Acidic if pI < 6
-Proteins Neutral if pI between: 6 - 8
-Proteins Basic if pI > 8