Question

1.     The primary sequence of the peptide listed below.

H2N - Asp-Thr-Phe-Lys-COOH

H₂N – D -T – F – K – COOH

Use the one letter amino acid code and identify from N-terminus to C-terminus.

a.     Determine the pI of the peptide. (Round to 2 decimal points)

b.     Would mutating residue #3 to Ala change the pI of the peptide? Explain.

c.      Which type of noncovalent interaction would the indicated residue side chain make at the given pH? (H-bond, Hydrophobic or Vander Waals, or Ionic bond or Salt bridge)

Residue 1 @ pH 5.0

Residue 2 @ pH 6.0

Residue 3 @ pH 11.0

Residue 4 @ pH 10.0

d.     Calculate the fraction of the peptides C-terminus protonated at pH 2.5 (Round to 2 decimal points)

Answer 1