For the following pentapeptides: Ser-Glu-Gly-His-Ala and Gly-His-Ala-Glu-Ser A. Compute their isoelectric pH (pI). Show full solution. Use standard pKa values. B. Do these peptides with the same amino acid composition have different net charges at pH 7.0? Explain briefly. C. Would you expect the titration curves of the two peptides to differ? Why or Why not?

An oligopeptide has the following amino acid sequence: NH2-Ala-Glu–Leu–Trp–Tyr-Ser–Gly–Lys–Leu-Ala–Arg-Ala-Phe-Ile-Pro–Gly-COOH a) Estimate the net electric charge of the molecule at pH 8.0 and pH 11.0. b) If the above peptide is passed through a cation exchange chromatographic column (that is, the matrix of the column has negative charges) stabilized at pH 8.0, would you expect it to be retained on the column? c) Indicates the number of fragments, and the sequence of each of them, that would be obtained when treating the peptide in question with: i) trypsin, ii) chymotrypsin.

A) Can you please tell me which of these A.A have a negative side chain? Names of choices in picture provided. B) Can you please tell me which A.A have a hydrophobic side chain and why?  Names and choices in picture provided. Thank You so much!!

1. Draw the appropriate titration curve for the tripeptide Met-Lys-Val starting at pH 1 and ending at pH 12. Label the pKas and the pI. Draw the two different forms of the molecule that is present at each buffering region. 2. Draw the structure of the peptide Arg-Met-His-Val-Glu and circle the coplanar atoms in one peptide bond. 3. Determine the pI for the peptide given in question 2 above.

Consider a protein in which a negatively charged glutamic acid side chain (pKa=4.2) makes a salt bridge (ion-ion interaction) with a positively charged histidine side chain (pKa=6.5). Part C: Justify your answer with calculations of partial charges on these amino acid side chains at pH=7.9.(Hint: Consider lessons from Coulomb's law, and the Henderson-Hasselbalch equation.)

Draw a schematic of the chemical structure of the Leu-Tyr-Met-Lys tetrapeptide, with the correct ionization at neutral pH (pH 7). Also, give an estimate the pl of this tetrapeptide (you are given that the pKa of any acidic R group is 4, the pKa of any basic R group is 11.5, and the pKa of the α-COOH is 2, and the a-NH3 is 9.5). Provide rationale!

A peptide with an amino acid sequence and molecular mass (1028.5193 Da) is given below HVMTLNLGEΚ Determine the maximum number of positive charges of this peptide. а. b. Determine the possible m/z ratio of this peptide at different charge states.

Discuss the reaction conditions you would need to carry out the PEGylation reaction of this peptide and explain how the pH affects the selectivity of these reactions.

Consider a protein in which a negatively charged glutamic acid side chain (pKa = 4.2) makes a salt bridge (ion-ion interaction) with a positively charged histidine side chain (pKa = 6.5). Part A Do you predict that this salt bridge will become stronger, become weaker, or be unaffected as pH increases from pH = 7.2 to pH = 7.8? The salt bridge will become stronger. The salt bridge will become weaker. The salt bridge will be unaffected. Submit Part B Previous Answers Correct At pH = 7.2 the glutamic acid (Glu) side chain will carry a charge of ~ -1 (at 3 pH units above the pKa for Glu, the side chain will be almost fully ionized); whereas the histidine (His) side chain will carry a charge of < +0.5 (at pH = pK₂ the charge on His would be +0.5; since pH = 7.2 is above its pKa, it will carry less (+) charge as it becomes more deprotonated). As the pH increase to 7.8, the charge on Glu will remain ~ -1 and the charge on His will decrease; thus, this salt bridge is predicted to become weaker…

For a peptide with a sequence listed below. Lys-Gln-Val-Arg-Glu-Phe-His-Asn-Asp-Tyr 1) Estimate the water-binding capacity of this peptide (g-water/g-peptide) at pH 7.