ASP-GLY-LYS-GLU-ILE-PHE. Examine the peptide you drew in problem 1 and calculate its pI. Show your work. a) pI = (pKa of amino acids) / 2 b) pI = pH where net charge is zero. c) pI = average pKa of acidic and basic side chains. d) pI = (pKa of GLU + pKa of LYS) / 2