1. a) Consider the polypeptide backbone represented below as a Richardson (Ribbon) Diagram. Draw the amino acid side chains coming off of the dot on the backbone as required. Be sure to show the most dominant ionization state for these side chains (pH of the buffer it 7.4) and draw the strongest IMF possible between the two sidechains that are close to each other (T and H, E and R, F and I). In the vicinity of any hydrogen bond, write the approximate length of the bond.

b) Draw the titration curve for Ly-Val using the provided grid, starting from the fully deprotonated form to the fully protonated form. Note that pH is being graphed versus equivalents of H+ added. Requirements: Indicated the pKa values on the graph, they must be in the right locations (pH and equivalents of H+ added) Put the letters A, B, C, etc., from parts a and b of this question, on the graph to show where these are the predominant species. Put a small circle around each equivalence point (Note: the pH of each equivalence point should be correct.) The pH value of the final equivalence point must be correct (see part e of this question). The starting pH can be an approximation.

c) If you start with 50.0 mL of a 0.25 M solution of Lys-Val in its fully deprotonated form and titrate it with 0.50 M HCl, calculate the pH of the solution just at the equivalence point when all protons have been added. Show your work. Make sure this is the final pH value you put in part b of this question. (Note: The use of the quadratic equation may be required)