Since the amino acid … (The commas between the amino acids indicate the sequence is unknown or unspecified.) Exercise 25-23* The following are acyl derivatives known to react with amines to give \(\ce{N}\)-acylated amines: Arrange these reagents in expected order of reactivity with the free amino group of a carboxyl-protected peptide, \(\ce{H_2N}-\)peptide\(\ce{-X}\), where \(\ce{X}\) is the carboxyl-protecting group. The degree of cross-linking determines the pore size of the gel. (At this point you should be able to deduce the sequence of five amino acids at the \(\ce{C}\)-terminus of eledoisin.) Exercise 25-2 Which of the amino acids in Table 25-1 are acidic amino acids and which basic amino acids? Exercise 25-4 Use Equations 25-1 and 25-2 to show that the isoelectric point of glycine is the average of the two p\(K_a\) values for the acid dissociation of glycine. c. Why do chiral azlactones derived from amino acids such as \(L\)-phenylalanine racemize easily on heating in ethanoic acid in the presence of ethanoate ion? b. Exercise 25-17 What problems might be encountered in using the 2,4-dinitrofluorobenzene method for determination of end groups on Gly-Lys-Ala? Exercise 25-7 Sketch the NMR spectrum showing the splitting pattern and chemical shifts you would anticipate for alanine dissolved in an excess of \(\ce{D_2O}\). The peptide is a powerful hypotensive agent. Assume that any side-chain functions in the peptide are suitably protected, but do not assume that the amino acids will couple with the peptide without suitable protection of their functional groups. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Explain. The racemic amino acid is first converted to a benzamide derivative to remove the basic character of the amino group. Write equations for the equilibria involved and assign p\(K_a\) values to each. Draw the structure of the azlactone derived from \(L\)-phenylalanine and ethanoic anhydride. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. The least basic amino nitrogen? Which of the hydrogens in this azlactone would you expect to be the most acidic? Deduce a possible structure from the following information: (1) Complete hydrolysis gives equal amounts of ammonia, Ala, Asp, Glu, Gly, Ile, Leu, Lys, Met, Phe, Pro, and Ser. What is the yield of the desired polypeptide isomer? First, 3-oxobutanoic acid labeled with \(\ce{^{18}O}\) at the ketone group and decarboxylated in ordinary water in the presence of the enzyme gives 2-propanone containing no \(\ce{^{18}O}\). Write equations, specifying the conditions as closely as possible, for reactions whereby a glucose unit of one polysaccharide chain could be linked to the glucose of another chain through an epichlorohydrin molecule. b. Would you expect ammonia or methanamine to give the blue color? (Consider exchanging \(\ce{Cl^-}\) for \(\ce{^-OH}\).). 25.E: Amino Acids, Peptides, and Proteins (Exercises), [ "article:topic", "dialyzed", "Exercises", "showtoc:no" ], 24.E: Organonitrogen Compounds II: Amides, Nitriles, & Nitro Compounds (Exercises), 26.E: More on Aromatic Compounds (Exercises). b. aspartic acid Specify the reagents required to accomplish each step. c. Show how the resonance method could be used to predict whether cytosine or 2-hydroxypyrimidine would have the greater tendency to be more stable in the lactam rather than the lactim form. Would you expect the reaction of 1-bromoglucose tetraethanoate with 2,4-diethoxypyrimidine to yield significant amounts of 6-ethoxy-1-(tetraethanoyl-\(D\)-glucosyl)-2-pyrimidone? Watch the recordings here on Youtube! Urea, the diamide of … Indicate the reaction mechanisms involved. Draw its full covalent structure. Exercise 25-34 Write equations for the mechanistic steps involved in hydrolysis of adenine deoxyribonucleoside to deoxyribose and adenine. Ion exchange with resin\(\ce{-S} \overset{\ominus}{\ce{O_3}} \overset{\oplus}{\ce{Na}}\) replaces \(\ce{Mg^{2+}}\) with \(\ce{Na^+}\), and with resin\(\ce{-SO_3H}\), \(\ce{Na^+}\) is replaced by \(\ce{H^+}\), thereby producing a dilute \(\ce{HCl}\) solution. The five sharp resonances marked at about \(110 \: \text{ppm}\) with * arise from tryptophan carbons marked with * in \(22\): a. Exercise 25-6 Indicate the approximate positions of \(\ce{C=O}\) and \(\ce{N-H}\) absorptions you would expect in the infrared spectra of (a) \(\overset{\ominus}{\ce{Cl}} \ce{H_3} \overset{\oplus}{\ce{N}} \ce{CH_2CO_2H}\) and (b) \(\ce{H_2NCH_2C} \overset{\ominus}{\ce{O_2}} \overset{\oplus}{\ce{Na}}\). Exercise 25-15 Suggest a synthetic route to proline from hexanedioic acid (adipic acid) that involves the transformations \(\ce{-CO_2H}- \rightarrow \ce{-NH_2}\), and \(\ce{-CH_2CO_2H}\) to \(\ce{-CHBrCO_2H}\). The equations for the acid-base equilibria of lysine in Section 25-2 show possible involvement of three forms of the monocation and three forms of the neutral acid. Explain. Exercise 25-27* A resin known as Sephadex that is useful in gel filtration is prepared from a polysaccharide that is cross-linked into a three-dimensional matrix with "epichlorohydrin", . Acid chlorides react with ammonia to give amides, also by an addition-elimination path, and these are reduced to amines by LiAlH 4. (At this point, you can deduce two possible sequences for Q.) The 6th example is a specialized procedure for bonding an amino group to a 3º-alkyl group (none of the previous methods accomplishes this).

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