Chapter 29: Q37. (page 1192)
What is the predominant form of each of the following amino acids at pH=11? What is the overall charge on the amino acid? (a)valine; (b)proline; (c)glutamic acid; (d)lysine?
Short Answer




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Chapter 29: Q37. (page 1192)
What is the predominant form of each of the following amino acids at pH=11? What is the overall charge on the amino acid? (a)valine; (b)proline; (c)glutamic acid; (d)lysine?




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What is the predominant form of each of the following amino acids at pH=1? What is the overall charge on the amino acid at this pH?(a)threonine ; (b)methionine; (c)aspartic acid; (d)arginine
Another method to form a peptide bond involves a two-step process:
[1] Conversion of a Boc-protected amino acid to a p-nitrophenyl ester.
[2] Reaction of the p-nitrophenyl ester with an amino acid ester.

Why does a p-nitrophenyl ester 鈥渁ctivate鈥 the carboxy group of the first amino acid to amide formation?
Would a p-methoxyphenyl ester perform the same function? Why or why not?

a. Draw the structure of the tripeptide A-A-A, and label the two ionizable functional groups.
b. What is the predominant form of A-A-A at pH=1?
c. The values for the two ionizable functional groups (3.39 and 8.03) differ considerably from the values of alanine (2.35 and 9.87;see table 29.1). Account for the observed differences.
Draw all the steps in the synthesis of each peptide from individual amino acids:
(a)Gly-Ala;
(b) Ile-Ala-Phe
Draw the organic products formed in each reaction.


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