Concept #1: Calculating Isoelectric Point Of Amino Acids With Ionizable R-Groups

Practice: What is the pI of His?

Practice: Electrophoresis separates molecules by migration through a gel only if they have a net charge. How do you expect an amino acid to migrate during electrophoresis when the pH = pI?

Practice: Draw Glu and calculate its isoelectric point. pKa1 = 9.67. pKa2 = 2.19. pKR = 4.25.

Practice: Calculate Cys’s pI. 

Practice: Calculate the pI of Arg. pKa1 = 9. pKa2 = 2.2. pKR = 12.5.

Practice: Calculate the pI of Asp.