Concept explainers
An octapeptide contains the following amino acids: Arg, Glu, His, Ile, Leu, Phe, Tyr, and Val. Carboxy peptidase treatment of the octapeptide forms Phe and a heptapeptide. Treatment of the octapeptide with chymotrypsin forms two tetrapeptides,
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Chapter 27 Solutions
Organic Chemistry (6th Edition)
- A chemically modified guanidino group is present in cimetidine (Tagamet), a widely prescribed drug for the control of gastric acidity and peptic ulcers. Cimetidine reduces gastric acid secretion by inhibiting the interaction of histamine with gastric H2 receptors. In the development of this drug, a cyano group was added to the substituted guanidino group to alter its basicity. Do you expect this modified guanidino group to be more basic or less basic than the guanidino group of arginine? Explain.arrow_forward22-47 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?arrow_forwardA 1.00-mg sample of a pure protein yielded on hydrolysis 0.0165 mg of leucine and 0.0248 mg of isoleucine. What is the minimum possible molar mass of the protein? (MMleucine=MMisoleucine=131g/mol)arrow_forward
- The dynorphins are a group of opioid peptides that play an importantrole in changes in the brain associated with cocaine addiction. One ofthese peptides, dynorphin A, contains the following amino acidsequence: Tyr–Gly–Gly–Phe–Leu–Arg–Arg–Ile–Arg–Pro–Lys–Leu–Lys.Draw the amino acids and peptide fragments formed when dynorphin A is treated with each reagent or enzyme: (a) chymotrypsin; (b) trypsin; (c)carboxypeptidase; (d) C6H5N=C=S.arrow_forwardDetermine the primary structure of an octapeptide from the following data: Acid-catalyzed hydrolysis gives 2 Arg, Leu, Lys, Met, Phe, Ser, and Tyr. Carboxypeptidase A releases Ser. Edman’s reagent releases Leu. Treatment with cyanogen bromide forms two peptides with the following amino acid compositions: 1. Arg, Phe, Ser 2. Arg, Leu, Lys, Met, Tyr Trypsin-catalyzed hydrolysis forms the following two amino acids and two peptides: 1. Arg 2. Ser 3. Arg, Met, Phe 4. Leu, Lys, Tyrarrow_forwardGlycine is a diprotic acid, which can potentially undergo two dissociation reactions, one for the a-amino group (-NH3), and the other for the carboxyl (-COOH) group. Therefore, it has two pKą values. The carboxyl group has a pK₁ of 2.34 and the a-amino group has a pK₂ of 9.60. Glycine can exist in fully deprotonated (NH₂-CH₂-COO-), fully protonated (NH3-CH₂-COOH), or zwitterionic form (NH3-CH₂-COO-). Match the pH values with the corresponding form of glycine that would be present in the highest concentration in a solution of th pH. fully deprotonated form NH,−CH,−COO- pH 11.9 pH 6.0 pH 8.0 fully protonated form NH3-CH₂-COOH pH 1.0 Answer Bank pH 7.0 zwitterionic form NH3-CH₂-COO-arrow_forward
- A tripeptide on hydrolysis produced glycine, alanine and leucine. The structures of these amino acids are shown below. On reaction with Edman’s reagent, leucine was released as the phenylhydantoin. Treatment of the tripeptide with carboxypeptidase gave glycine. Draw the structure of the tripeptide.arrow_forwardDetermine the amino acid sequence of a polypeptide from the following data:Acid-catalyzed hydrolysis gives Ala, Arg, His, 2 Lys, Leu, 2 Met, Pro, 2 Ser, Thr, and Val.Carboxypeptidase A releases Val.Edman’s reagent releases PTH-Leu.Trypsin-catalyzed hydrolysis gives three peptides and a single amino acid:1. Arg, Leu, Ser 3. Lys2. Met, Pro, Ser, Thr, Val 4. Ala, His, Lys, Metarrow_forwardGive the amino acid sequence of a hexapeptide that contains the amino acids Ala, Val, Ser, Ile, Gly, Tyr, and forms the following fragments when partially hydrolyzed with HCl: Gly–Ile–Val, Ala–Ser–Gly, and Tyr–Ala.arrow_forward
- Hydrolysis of decapeptide P with the enzyme trypsin affords the following fragments: Gly-Asp, Ala-Cys-Lys, Leu-Trp- Val-Gly-Arg. Hydrolysis with chymotrypsin yields: Leu-Trp, Val-Gly-Arg-Ala-Cys-Lys-Gly-Asp. What is the amino acid sequence of P?arrow_forwardDetermine the amino acid sequence of a polypeptide from the following data:Complete hydrolysis of the peptide yields Ala, Arg, Gly, 2 Lys, Met, Phe, Pro, 2 Ser, Tyr, and Val.Treatment with Edman’s reagent releases PTH-Val.Carboxypeptidase A releases Ala. Treatment with trypsin yields the following three peptides:1. Gly, Lys, Met, Tyr 2. Ala, Lys, Phe, Pro, Ser 3. Arg, Ser, Valarrow_forwardDetermine the amino acid sequence of a polypeptide from the following data: Complete hydrolysis of the peptide yields Ala, Arg, Gly, 2 Lys, Met, Phe, Pro, 2 Ser, Tyr, and Val. Treatment with Edman’s reagent releases PTH-Val. Carboxypeptidase A releases Ala. Treatment with cyanogen bromide yields the following two peptides: 1. Ala, 2 Lys, Phe, Pro, Ser, Tyr 2. Arg, Gly, Met, Ser, Val Treatment with trypsin yields the following three peptides: 1. Gly, Lys, Met, Tyr 2. Ala, Lys, Phe, Pro, Ser 3. Arg, Ser, Val Treatment with chymotrypsin yields the following three peptides: 1. 2 Lys, Phe, Pro 2. Arg, Gly, Met, Ser, Tyr, Val 3. Ala, Serarrow_forward
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