Amino Acid Titration

Using the information in Table 2.1 of your book,

1. Draw the theoretical curve for the complete titration of

2. Knowing that pI is the pH at which a molecule has an average charge of exactly zero, calculate the pIs of the above amino acids.

 

 

Protein Charge Problems

For the purposes of estimating charge of a protein, it is reasonable to assume that if the pH the protein is in is more than one pH unit above the pKa of a particular group, the proton of the group is off. On the other hand, if the pH is more than on e unit below the pKa of a particular group, the proton is on. Using that information and Table 2.1 of your book, calculate the charge on the following polypeptide at the pHs below

Amino end -Gly-Arg-Cys-Asp-Leu-Pro-Ile-Ala-Ser-Trp-Lys - Carboxyl end

a. pH = 2
b. pH = 5.5
c. pH = 9.5
d. pH = 14