2. Use the table to answer the following questions about the peptide you drew in question 1. Amino PK1 pk2 PKR Acid (-COOH) (-NH3+) (R-group) Lys 2.18 8.95 10.53 Thr 2.11 9.62 Gln 2.17 9.13 His 1.82 9.17 6.00 Val 2.32 9.62 a. Determine the net charge of the peptide at pH 0 and 14? b. Estimate the pl for this peptide. Is this an acidic or basic peptide?

A mixture of Aspartic Acid (pl 2.98), Histidine (pl 7.59), Lysine (pl 9.74), Phenylalanine (pl 5.48) and Threonine (pl 6.53) are separated by cation exchange chromatography. What is the order of elution of these amino acids if you use gradient buffer system from pH 10 to pH 2. v First 1. Aspartic Acid v Second 2. Histidine v Third 3. Lysine 4. Phenylalanine v Fourth 5. Threonine v Fifth 6. No separation

5. Refer to Model 2 for information relevant to this question. A sample of the peptide Lys-Glu-Ser has a net charge of zero between what two pH values? What is the pl of Lys-Glu-Ser? Model 2: The pl of a peptide is determined by examining the ionizable groups. The protonated and unprotonated forms of each ionizable group are in equilibrium. Consider the peptide Lys-Glu-Ser shown below at pH 7.2. The complete structure is on on the left and a stylized structure with just the ionizable groups is on the right. While the N-terminal is depicted as protonated, a sample of Lys-Glu-Ser is composed of a population of molecules and within that population some molecules contain a non-protonated N-terminal group at pH 7.2. may H3N* COO- H3N-CH-CIN-CH C N-CH C- H. pK 3.5 OH H. pK= 8.5 COO- CH2 CH2 CH2 NH, pK 10.0 pK 4.2 CH2 CH2 OH CH2 c=0

Please don't provid3e handwritten solution ....

Can you please help find the net charge?

2. Consider the peptide Trp-Arg-Glu-Cys-Gly-Tyr. For the drawings requested below, please show in zig-zag style, from amino to carboxy terminus, with correct stereochemistry a. Draw the predominant form at pH = 2 b. Draw the predominant form at pH = 5 c. Draw the predominant form at pH = 7 d. Draw the predominant form at pH = 12

What is the charge of this peptide at pH 7?

Which of the following is incorrect about the peptide Arg-Asp-Cys-Tyr-Gln-Arg-Glu? O a. Its estimated MW is 770 Da b. None; all the other choices are correct OC. At pH 7, it has a net charge of zero O d. At pH 7, it has six charged groups

1. Consider the peptides P-A-I-G-E and M-A-T-T. a. Draw the structure of each peptide at a pH of 7.0 b. Draw the structure of each peptide at a pH of 12.0 c. Calculate the pl of both peptides. Based on your answer, do you think these two peptides can be separated using ion exchange chromatography at a pH of 5? Explain.

1. a. Draw the following pentapeptide: lysine-leucine-aspartate-threonine-phenylalanine b. Label the amino and carboxyl terminus of your peptide c. Label each amino acid residue with one and three letter abbreviations d. Label the alpha carbons e. Label the bonds around which phi and psi rotational angles occur f. Which amino acid in this chain is most likely to be phosphorylated? Which amino acid is most likely to be acetylated?