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?

1. Which peptide would be more soluble at pH 7.0, (Val)₂₀ or (Asp)₂₀ ? at pH 3.0, (Gly-Glu-Val)

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 ....

1. Draw an approximate titration curve of the following amino acid. Label the approximate isoelectric point of arginine on the curve and be sure to label the axis of the graph appropriately. You DO NOT need to draw the structure of this amino acid here. Pk1= 1.92, pk2=8.99 and pk3=12.48. Show your work for determining the isoelectric point. You can draw out your curve within the text box or upload a drawing. A▾ B I - I B 7

What are the charges of the following amino acids peptides at ph 14? 1. GLAVV 2. RRKKQ

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

27. Draw palmitic acid, identify a, B and w carbons, write out its short hand notation 28. Examine the peptide sequence below and then answer the questions: H2N-Gly- Leu- Ala-Asp-Cys-Asn-Trp-lle-Ser-Phe-Lys-Cys-Arg-Pro-coOH a. Circle the asparagine residue b. A possible intramolecular disulfide bond can be formed within this peptide between which two residues? c. Circle one residue which has a positively charged side chain under pH 7.4 d. Circle one residue which has a negatively charged side chain under pH 7.4 e. Circle the residue which can be phosphorylated

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.