Which peptides is more likely to take up on alpha-helical structure? Explain. Top: Leu-Lys-Ala-Glu-Asn-Asp-Glu-Ala-Ala-Arg-Ala-Met-Ser-Glu-Ala Bottom: Cys-Arg-Ala-Gly-Gly-Phe-Pro-Trp-Asp-Gln-Pro-Gly-Tyr-Ser-Asn

What special role does the amino acid cysteine have in the peptides vasopressin and oxytocin?

22-59 What is the effect of salt bridges on the tertiary structure of proteins?

22-47 How many different tetrapeptides can be made (a) if the peptides contain the residues of asparagine, proline, serine, and metbionine and (b) if all 20 amino acids can be used?

Using both three- and one-letter codes for amino acids, write the structures of all possible peptides containing the following amino acids: (a) Val, Ser, Leu (b) Ser, Leu2, Pro

22-42 (a) How many atoms of the peptide bond lie in the same plane? (b) Which atoms are they?

The use of salt bridges or hydrophobic interactions (or pockets) to stabilize interactions between more distant amino acids within a single polypeptide, is a demonstration of protein TERTIARY structure. True False

You are studying a peptide in the sky bison that has the sequence below. Ala-Met-Cys-Lys-Trp-Glu-Lys-Gln-Pro-Asp-Gly-Met-Glu-Cys-Ala-Phe Suppose this is a portion of the sequence of a large folded protein. Where in the protein would you expect to find the highlighted AAs? On the interior of the protein because these AA are nonpolar On the exterior of the protein because these AA are hydrophilic On the interior of the protein because disulfide bonds are nonpolar Not enough information to tell

5. Arg and Lys Asp and Lys Pro and Glu Among these amino acid combinations listed above, only the combination of Asp and Lys have side chains with groups that have the greatest ability to stabilize the tertiary structure of a protein. Explain in your own words and by drawing (1) why Asp and Lys side chain interaction stabilizes the tertiary structure of a protein, and (2) why the pairs of Arg and Lys & Pro and Glu cannot provide the stability to the protein structure.

A peptide has the sequence   Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly   The p?a values for the peptide’s side chains, terminal amino groups, and carboxyl groups are provided in the table. Amino acid Amino pKa Carboxyl pKa Side‑chain pKa glutamate 9.609.60 2.342.34 4.254.25 histidine 9.179.17 1.821.82 6.006.00 tryptophan 9.399.39 2.382.38   serine 9.159.15 2.212.21   glycine 9.609.60 2.342.34   leucine 9.609.60 2.362.36   arginine 9.049.04 2.172.17 12.4812.48 proline 10.9610.96 1.991.99       Calculate the net charge of the molecule at pH 11 and estimate the isoelectric point (pI)(pI) for this peptide.