How long is an ?-helix that contains 74 amino acids? How

Explain why amino acids, unlike most amines and carboxylic acids, are insoluble in diethyl ether.

Alanine has p Ka values of 2.34 and 9.69. At what pH will alanine exist in the indicated form?

Show the peptides that would result from cleavage by the indicated reagent: a. Val-Arg-Gly-Met-Arg- Ala-Ser by carboxypeptidase A b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide c. Arg- Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Which would have a higher percentage of negative charge at physiological pH (7.4), leucine with pI = 5.98 or asparagine with pI = 5.43?

Aspartame has a pI of 5.9. Draw its prevailing form at physiological pH (7.4).

Draw the form of aspartate that predominates at the following pH values:

A professor was preparing a manuscript for publication in which she reported that the pI of the tripeptide Lys-Lys-Lys was 10.6. One of her students pointed out that there must be an error in her calculations because the p Ka of the e -amino group of lysine is 10.8 and the pI of the tripeptide has to be greater than any of its individual p Ka values. Was the student correct?

A mixture of amino acids that do not separate sufi ciently when a single technique is used can often be separated by two-dimensional chromatography. In this technique, the mixture of amino acids is applied to a piece of i lter paper and separated by chromatographic techniques. The paper is then rotated 90, and the amino acids are further separated by electrophoresis, producing a type of c hromatogram called a ngerprint. Identify the spots in the i ngerprint obtained from a mixture of Ser, Glu, Leu, His, Met, and Thr. E

Determine the amino acid sequence of a polypeptide from the following data: Complete hydrolysis of the peptide yields Arg, 2 Gly, Ile, 3 Leu, 2 Lys, 2 Met, 2 Phe, Pro, Ser, 2 Tyr, and Val. Treatment with Edmans reagent releases PTH-Gly. Carboxypeptidase A releases Phe. Treatment with cyanogen bromide yields the following three peptides: 1. Gly-Leu-Tyr-Phe-Lys-Ser-Met 2. Gly-Leu-Tyr-Lys-Val- Ile-Arg-Met 3. Leu-Pro-Phe Treatment with trypsin yields the following four peptides: 1. Gly-Leu-Tyr- Phe-Lys 3. Val-Ile-Arg 2. Ser-Met-Gly-Leu-Tyr-Lys 4. Met-Leu-Pro-Phe

Explain the difference in the p Ka values of the carboxyl groups of alanine, serine, and cysteine.

Which would be a more effective buffer at physiological pH, a solution of 0.1 M glycylglycylglycylglycine or a solution of 0.2 M glycine?

Identify the location and type of charge on the hexapeptide Lys-Ser-Asp-Cys-His-Tyr at each of the following pH values: a. pH = 1 b. pH = 5 c. pH = 7 d. pH = 12

Draw the product obtained when a lysine side chain in a polypeptide reacts with maleic anhydride.

After the polypeptide shown here was treated with maleic anhydride, it was hydrolyzed by trypsin. (After a polypeptide is treated with maleic anhydride, trypsin will cleave the polypeptide only on the C- side of arginine.) Gly-Ala-Asp-Ala-Leu-Pro-Gly-Ile-Leu-Val-Arg-Asp-Val-Gly-Lys-Val-Glu-Val-Phe-Glu- Ala-GlyArg-Ala-Glu-Phe-Lys-Glu-Pro-Arg-Leu-Val-Met-Lys-Val-Glu-Gly-Arg-Pro-Val-Gly-Ala-Gly-Leu- Trp a. After a polypeptide is treated with maleic anhydride, why does trypsin no longer cleave it on the C-side of lysine? b. How many fragments are obtained from the polypeptide? c. In what order would the fragments be eluted from an anion-exchange column using a buffer of pH = 5?

Treatment of a polypeptide with 2-mercaptoethanol yields two polypeptides with the following primary structures:

Show how aspartame can be synthesized using DCC.

a -Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acidcatalyzed hydrolysis. a. Draw the structures of the two intermediates formed in this reaction. b. What amino acid is formed when the aldehyde that is used is 3-methylbutanal? c. What aldehyde would be needed to prepare isoleucine?

Reaction of a polypeptide with carboxypeptidase A releases Met. The polypeptide undergoes partial hydrolysis to give the following peptides. What is the sequence of the polypeptide? 1. Ser, Lys, Trp 4. Leu, Glu, Ser 7. Glu, His 10. Glu, His, Val 2. Gly, His, Ala 5. Met, Ala, Gly 8. Leu, Lys, Trp 11. Trp, Leu, Glu 3. Glu, Val, Ser 6. Ser, Lys, Val 9. Lys, Ser 12. Ala, Met

a. How many different octapeptides can be made from the 20 naturally occurring amino acids? b. How many different proteins containing 100 amino acids can be made from the 20 naturally occurring amino acids?

Glycine has p Ka values of 2.3 and 9.6. Would you expect the p Ka values of glycylglycine to be higher or lower than these values?

A mixture of 15 amino acids gave the i ngerprint shown here (see Problem 54 ). Identify the spots. ( Hint 1: Pro reacts with ninhydrin to produce a yellow color; Phe and Tyr produce a green color. Hint 2: Count the number of spots before you start.)

Write the mechanism for the reaction of an amino acid with di- tert -butyl dicarbonate.

Dithiothreitol reacts with disuli de bridges in the same way that 2-mercaptoethanol does. With dithiothreitol, however, the equilibrium lies much more to the right. Explain.

Show how valine can be prepared by a. a HellVolhardZelinski reaction. d. a N -phthalimidomalonic ester synthesis. b. a Strecker synthesis. e. an acetamidomalonic ester synthesis.

Show how valine can be prepared by a. a HellVolhardZelinski reaction. d. a N -phthalimidomalonic ester synthesis. b. a Strecker synthesis. e. an acetamidomalonic ester synthesis.

Propose a mechanism for the rearrangement of the thiazoline obtained from the reaction of Edmans reagent with a peptide to a PTH-amino acid ( page 1083 ). ( Hint : Thioesters are susceptible to hydrolysis.)

A normal polypeptide and a mutant of the polypeptide were hydrolyzed by an endopeptidase under the same conditions. The normal and mutant polypeptide differ by one amino acid. The i ngerprints of the peptides obtained from the two polypeptides are shown here. What kind of amino acid substitution occurred as a result of the mutation? (That is, is the substituted amino acid more or less polar than the original amino acid? Is its pI lower or higher?) ( Hint : Photocopy the i ngerprints, cut them out, and overlay them.)

Determine 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 Edmans 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, Ser

Problem 2P a. Which isomer—(R)-alanine or (S)-alanine—is D-alanine? b. Which isomer—(R)-aspartate or (S)-aspartate—is D-aspartate? c. Can a general statement be made relating R and S to D and L?

a. Explain why, when the imidazole ring of histidine is protonated, the double-bonded nitrogen is the nitrogen that accepts the proton. b. Explain why, when the guanidino group of arginine is protonated, the double-bonded nitrogen is the nitrogen that accepts the proton.

Do any other amino acids in Table \(22.2\) have more than one asymmetric center? Equation Transcription: Text Transcription: 22.2

Problem 5P Alanine has pKa values of 2.34 and 9.69. Therefore, alanine will exist predominately as azwitterion in an aqueous solution with pH > ____ and pH < ____.

Problem 6P Why are the carboxylic acid groups of the amino acids so much more acidic (pKa ~ 2) than a carboxylic acid such as acetic acid (pKa = 4.76)?

Problem 7P Draw the predominant form for each of the following amino acids at physiological pH (7.4): a. aspartate c. glutamine e. arginine b. histidine d. lysine f. tyrosine

Problem 8P Draw the form of glutamic acid that predominates in a solution with the following pH: a. pH = 0 ________________ b. pH = 3 ________________ c. pH = 6 ________________ d. pH = 11

Problem 9P a. Why is the pKa of the glutamate side chain greater than the pKa of the aspartate side chain? b. Why is the pKa of the arginine side chain greater than the pKa of the lysine side chain?

Problem 10P Explain why the pI of lysine is the average of the pKa values of its two protonatedamino groups.

Problem 11P Calculate the pI of each of the following amino acids: a. asparagine b. arginine c. serine d. aspartate

Problem 12P a. Which amino acid has the lowest pI value? b. Which amino acid has the highest pI value? c. Which amino acid has the greatest amount of negative charge at pH = 6.20? d. Which amino acid has a greater negative charge at pH = 6.20, glycine or methionine?

Problem 13P Explain why the pI values of tyrosine and cysteine cannot be determined by the method just described.

Problem 14P What aldehyde is formed when valine is treated with ninhydrin?

Problem 15P A mixture of seven amino acids (glycine, glutamate, leucine, lysine, alanine, isoleucine, and aspartate) is separated by chromatography. Explain why only six spots show up when the chromatographic plate is coated with ninhydrin and heated.

Why are buffer solutions of increasingly higher pH used to elute the column that generates the chromatogram shown in Figure \(22.5\) ? ( Elute means wash out with a solvent.) Equation Transcription: Text Transcription: 22.5

Explain the order of elution (with a buffer of pH \(4\)) of the following pairs of amino acids through a column packed with Dowex \(50\) ( Figure \(22.3\) ): a. aspartate before serine c. valine before leucine b. serine before alanine d. tyrosine before phenylalanine Equation Transcription: Text Transcription: 4 50 22.3

Problem 18P In what order would histidine, serine, aspartate, and valine be eluted with a buffer of pH 4 from a column containing an anion-exchange resin (Dowex 1)?

Problem 19P Why is excess ammonia used in the preceding reaction?

Cells can also convert a -keto acids into amino acids, but because the reagents organic chemists use for this reaction are not available in cells, they carry out this reaction by a different mechanism ( Section \(24.5\) ) . a. What amino acid is obtained from the reductive amination of each of the following metabolic intermediates in a cell? b. What amino acids are obtained from the same metabolic intermediates when the amino acids are synthesized in the laboratory? Equation Transcription: Text Transcription: 24.5

What amino acid would be formed using the N-phthalimidomalonic ester synthesis when the following alkyl halides are used in the third step? a. \(\mathrm{CH}_{3} \mathrm{CHCH}_{2} \mathrm{Br}\) b.\(\mathrm{CH}_{3} \mathrm{SCH}_{2} \mathrm{CH}_{2} \mathrm{Br}\) \(\mathrm{CH}_{3}\) Equation Transcription: CH3CHCH2Br CH3SCH2CH2Br CH3 Text Transcription: CH_3CHCH_2Br CH_3SCH_2CH_2Br CH_3

Problem 22P What alkyl halide would you use in the acetamidomalonic ester synthesis to prepare a. Lysine? b. phenylalanine?

What amino acid would be formed when the aldehyde used in the Strecker synthesis is a. acetaldehyde? b. 2-methylbutanal? c. 3-methylbutanal?

Problem 24P Pig liver esterase is an enzyme that catalyzes the hydrolysis of esters. It hydrolyzes esters of L-amino acids more rapidly than esters of D-amino acids. How can this enzyme be used to separate a racemic mixture of amino acids?

Problem 25P Draw the tetrapeptide Ala-Thr-Asp-Asn and indicate the peptide bonds.

Problem 26P Using the three-letter abbreviations, write the six tripeptides consisting of Ala, Gly, and Met.

Problem 27P Draw the resonance contributors of the peptide bond in the less stable configuration.

Problem 28P Which bonds in the backbone of a peptide can rotate freely?

Problem 29P What is the configuration about each of the asymmetric centers in aspartame?

Glutathione is a tripeptide whose function is to destroy harmful oxidizing agents in the body. Oxidizing agents are thought to be responsible for some of the effects of aging and to play a causative role in cancer. Glutathione removes oxidizing agents by reducing them. In the process, glutathione is oxidized, resulting in the formation of a disulfide bond between two glutathi-one molecules. An enzyme subsequently reduces the disulfide bond, returning glutathione to its original condition so it can react with another oxidizing agent. a. What amino acids make up glutathione? b. What is unusual about glutathione’s structure? (If you cannot answer this question, draw the structure you would expect for the tripeptide, and compare your structure with the actual structure.)

What dipeptides would be formed by heating a mixture of valine and N-protected leucine?

Problem 32P Suppose you are trying to synthesize the dipeptide Val-Ser. Compare the product that would be obtained if thionyl chloride were used to activate the carboxyl group of N-protected valine with the product that would be obtained if it were activated with DCC.

Problem 33P Show the steps in the synthesis of the tetrapeptide Leu-Phe-Ala-Val.

Problem 34P a. Calculate the overall yield of bradykinin when the yield for the addition of each amino acid to the chain is 70%. b. What would be the overall yield of a peptide containing 15 amino acids if the yield for the incorporation of each is 80%?

Problem 35P Show the steps in the synthesis of the tetrapeptide in Problem 33, using Merrifield’s method. PROBLEM 33 Show the steps in the synthesis of the tetrapeptide Leu-Phe-Ala-Val.

Problem 36P Write the mechanism for the reaction of a cysteine side chain with iodoacetic acid.

Problem 37P In determining the primary structure of insulin, what would lead you to conclude that it had more than one polypeptide chain?

A decapeptide undergoes partial hydrolysis to give peptides whose amino acid compositions are shown. Reaction of the intact decapeptide with Edman’s reagent releases PTH-Gly. What is the sequence of the decapeptide? 1. Ala, Trp 3. Pro, Val 5. Trp, Ala, Arg 7. Glu, Ala, Leu 2. Val, Pro, Asp 4. Ala, Glu 6. Arg, Gly 8. Met, Pro, Leu, Glu

Problem 39P Why doesn’t cyanogen bromide cleave on the C-side of cysteine?

Problem 40P Indicate the peptides that would result from cleavage by the indicated reagent: a. His-Lys-Leu-Val-Glu-Pro-Arg-Ala-Gly-Ala by trypsin b. Leu-Gly-Ser-Met-Phe-Pro-Tyr-Gly-Val by chymotrypsin

Problem 41P Determine 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, Tyr

Problem 42P Three peptides were obtained from a trypsin digestion of two different polypeptides. In each case, indicate the possible sequences from the given data and tell what further experiment should be carried out in order to determine the primary structure of the polypeptide. a. 1. Val-Gly-Asp-Lys 2. Leu-Glu-Pro-Ala-Arg 3. Ala-Leu-Gly-Asp b. 1. Val-Leu-Gly-Glu 2. Ala-Glu-Pro-Arg 3. Ala-Met-Gly-Lys

Problem 44P How long is an ?-helix that contains 74 amino acids? How long is a fully extended peptide chain that contains the same number of amino acids? (The distance between consecutive amino acids in a fully extended chain is 3.5 Å; the repeat distance of an ?-helix is 5.4 Å.)

Problem 45P How would a protein that resides in the interior of a membrane fold, compared with the water-soluble protein just discussed?

Problem 46P a. Which would have the greatest percentage of polar amino acids, a spherical protein, a cigar shaped protein, or a subunit of a hexamer? b. Which would have the smallest percentage of polar amino acids?

Problem 47P Explain why amino acids, unlike most amines and carboxylic acids, are insoluble in diethyl ether.

Alanine has \(\mathrm{pK}_{\mathrm{a}}\) values of \(2.34\) and \(9.69\). At what pH will alanine exist in the indicated form? Equation Transcription: pKa Text Transcription: pK_a 2.34 9.69

Problem 49P Indicate the peptides that would result from cleavage by the indicated reagent: a. Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide c. Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Problem 50P Which would have a higher percentage of negative charge at physiological pH (7.4), leucine with pI = 5.98 or asparagine with pI = 5.43?

Problem 51P Aspartame has a pI of 5.9. Draw its prevailing form at physiological pH (7.4).

Problem 52P Draw the form of aspartate that predominates at a. pH = 1.0 ________________ b. pH = 2.6 ________________ c. pH = 6.0 ________________ d. pH =11.0

A professor was preparing a manuscript for publication in which she reported that the pI of the tripeptide Lys-Lys-Lys was \(10.6\). One of her students pointed out that there must be an error in her calculations because the \(\mathrm{pK}_{\mathrm{a}}\) of the \(\varepsilon\)-amino group of lysine is \(10.8\) and the p? of the tripeptide has to be greater than any of its individual \(\mathrm{pK}_{\mathrm{a}}\) values. Was the student correct?I Equation Transcription: pKa Text Transcription: 10.6 epsilon 10.8 pK_a

Problem 54P A mixture of amino acids that do not separate sufficiently when a single technique is used can often be separated by two-dimensional chromatography. In this technique, the mixture of amino acids is applied to a piece of filter paper and separated by chromatographic techniques.The paper is then rotated 90°, and the amino acids are further separated by electrophoresis, producing a type of chromatogram called a fingerprint. Identify the spots in the fingerprint obtained from a mixture of Ser, Glu, Leu, His, Met, and Thr.

Problem 55P Determine the amino acid sequence of a polypeptide from the following data: Complete hydrolysis of the peptide yields Arg, 2 Gly, Ile, 3 Leu, 2 Lys, 2 Met, 2 Phe, Pro, Ser, 2 Tyr, and Val. Treatment with Edman’s reagent releases PTH-Gly. Carboxypeptidase A releases Phe. Treatment with cyanogen bromide yields the following three peptides: 1. Gly-Leu-Tyr-Phe-Lys-Ser-Met 2. Gly-Leu-Tyr-Lys-Val-Ile-Arg-Met 3. Leu-Pro-Phe Treatment with trypsin yields the following four peptides: 1. Gly-Leu-Tyr-Phe-Lys 3. Val-Ile-Arg 2. Ser-Met-Gly-Leu-Tyr-Lys 4. Met-Leu-Pro-Phe

Problem 57P Which would be a more effective buffer at physiological pH, a solution of 0.1 M glycylglycylglycylglycine or a solution of 0.2 M glycine?

Problem 56P Explain the difference in the pKa values of the carboxyl groups of alanine, serine, and cysteine.

Problem 58P Identify the location and type of charge on the hexapeptide Lys-Ser-Asp-Cys-His-Tyr at each of the following pH values: a. pH = 1 b. pH = 5 c. pH = 7 d. pH = 12

Draw the product obtained when a lysine side chain in a polypeptide reacts with maleic anhydride.

Problem 60P After the polypeptide shown here was treated with maleic anhydride, it was hydrolyzed by trypsin. (After a polypeptide is treated with maleic anhydride, trypsin will cleave the polypeptide only on the C-side of arginine.) Gly-Ala-Asp-Ala-Leu-Pro-Gly-Ile-Leu-Val-Arg-Asp-Val-Gly-Lys-Val-Glu-Val-Phe-Glu-Ala-GlyArg-Ala-Glu-Phe-Lys-Glu-Pro-Arg-Leu-Val-Met-Lys-Val-Glu-Gly-Arg-Pro-Val-Gly-Ala-Gly-Leu-Trp a. After a polypeptide is treated with maleic anhydride, why does trypsin no longer cleave it on the C-side of lysine? b. How many fragments are obtained from the polypeptide? c. In what order would the fragments be eluted from an anion-exchange column using a buffer of pH = 5?

Problem 61P Treatment of a polypeptide with 2-mercaptoethanol yields two polypeptides with the following primary structures: Val-Met-Tyr-Ala-Cys-Ser-Phe-Ala-Glu-SerSer-Cys-Phe-Lys-Cys-Trp-Lys-Tyr-Cys-Phe-Arg-Cys-Ser Treatment of the original intact polypeptide with chymotrypsin yields the following peptides: 1. Ala, Glu, Ser 3. Tyr, Val, Met 5. Ser, Phe, 2 Cys, Lys, Ala, Trp 2. 2 Phe, 2 Cys, Ser 4. Arg, Ser, Cys 6. Tyr, Lys Determine the positions of the disulfide bridges in the original polypeptide.

Problem 62P Show how aspartame can be synthesized using DCC.

\(\alpha\)-Amino acids can be prepared by treating an aldehyde with ammonia/trace acid, followed by hydrogen cyanide, followed by acid-catalyzed hydrolysis. a. Draw the structures of the two intermediates formed in this reaction. b. What amino acid is formed when the aldehyde that is used is 3-methylbutanal? c. What aldehyde would be needed to prepare isoleucine?

Problem 64P Reaction of a polypeptide with carboxypeptidase A releases Met. The polypeptide undergoes partial hydrolysis to give the following peptides. What is the sequence of the polypeptide? a. Ser, Lys, Trp b. Gly, His, Ala c. Glu, Val, Ser d. Leu, Glu, Ser e. Met, Ala, Gly f. Ser, Lys, Val g. Glu, His h. Leu, Lys, Trp i. Lys, Ser j. Glu, His, Val k. Trp, Leu, Glu l. 1. Ala, Met

a. How many different octapeptides can be made from the 20 naturally occurring amino acids? b. How many different proteins containing 100 amino acids can be made from the 20 naturally occurring amino acids?

Problem 66P Glycine has pKa values of 2.3 and 9.6. Would you expect the pKa values of glycylglycine to be higher or lower than these values?

A mixture of \(15\) amino acids gave the fingerprint shown here (see Problem \(54\) ). Identify the spots. ( Hint 1: Pro reacts with ninhydrin to produce a yellow color; Phe and Tyr produce a green color. Hint 2: Count the number of spots before you start.) Equation Transcription: Text Transcription: 15 54

Write the mechanism for the reaction of an amino acid with di-tert-butyl dicarbonate.

Dithiothreitol reacts with disuli de bridges in the same way that \(2\)-mercaptoethanol does. With dithiothreitol, however, the equilibrium lies much more to the right. Explain. Equation Transcription: Text Transcription: 2

Show how valine can be prepared by a. a Hell–Volhard–Zelinski reaction. b. a Strecker synthesis. c. a reductive amination. d. a N-phthalimidomalonic ester synthesis. e. an acetamidomalonic ester synthesis.

Problem 71P A chemist wanted to test his hypothesis that the disulfide bridges that form in many proteins do so after the minimum energy conformation of the protein has been achieved. He treated a sample of an enzyme that contained four disulfide bridges, with 2-mercaptoethanol and then added urea to denature the enzyme. He slowly removed these reagents so that the enzyme could re-fold and re-form he disulfide bridges. The enzyme he recovered had 80% of its original activity. What would be the percent activity in the recovered enzyme if disulfide bridge formation were entirely random rather than determined by the tertiary structure? Does this experiment support his hypothesis?

Propose a mechanism for the rearrangement of the thiazoline obtained from the reaction of Edman’s reagent with a peptide to a PTH-amino acid ( page \(1083\) ). ( Hint : Thioesters are susceptible to hydrolysis.) Equation Transcription: Text Transcription: 1083

A normal polypeptide and a mutant of the polypeptide were hydrolyzed by an endopeptidase under the same conditions. The normal and mutant polypeptide differ by one amino acid. The fingerprints of the peptides obtained from the two polypeptides are shown here. What kind of amino acid substitution occurred as a result of the mutation? (That is, is the substituted amino acid more or less polar than the original amino acid? Is its pI lower or higher?) ( Hint : Photocopy the i ngerprints, cut them out, and overlay them.)

Problem 74P Determine the amino acid sequence of a polypeptide from the following data: a. Complete hydrolysis of the peptide yields the following amino acids: Ala, Arg, Gly, 2 Lys, Met, Phe, Pro, 2 Ser, Tyr, Val. b. Treatment with Edman’s reagent gives PTH-Val. c. Carboxypeptidase A releases Ala. d. Treatment with cyanogen bromide yields the following two peptides: 1. Ala, 2 Lys, Phe, Pro, Ser, Tyr 2. Arg, Gly, Met, Ser, Val e. Treatment with trypsin yields the following three peptides: 1. Gly, Lys, Met, Tyr 2. Ala, Lys, Phe, Pro, Ser 3. Arg, Ser, Val f. Treatment with chymotrypsin yields the following three peptides: 1. 2 Lys, Phe, Pro 2. Arg, Gly, Met, Ser, Tyr, Val 3. Ala, Ser