Exam 24: Amino Acids, Peptides, and Proteins

A polypeptide was treated with a certain enzyme to yield the following amino acid sequences. What enzyme was used to induce the observed fragmentations? Val-Pro-Phe Leu-Ser-Lys-Glu-Trp Arg-Ile-Ser-Ser-Leu-Tyr

Which of the following amino acids does not contain an aromatic R-group?

Complete hydrolysis of a hexapeptide gives 2 Gly, Leu, Phe, Pro, and Tyr. Reaction of the peptide with phenylisothiocyanate gave the phenylthiohydantoin of Pro. Partial hydrolysis of the peptide gave the following fragments: Phe-Gly-Tyr, Gly-Phe-Gly, Pro-Leu-Gly, Leu-Gly-Phe. What is the structure of the peptide?

Which of the following amino acids are classified as essential amino acids? (More than one answer is possible.)

What is the one letter symbol of the amino acid below?

Provide the structure of the major organic product which results when L-histidine is treated with benzyl chloroformate.

Show the mechanism for the hydrolysis of the following dipeptide?

Provide a reasonable synthesis of Gly-Val from the individual amino acids.

Which amino acid has an indole ring in its side chain?

Which of the following indicators is commonly used to visualize bands of amino acids?

How is the enzyme chymotrypsin used in peptide structure determination?

Draw the Fischer projection of L-glutamic acid at a pH of 12.

Provide a detailed, stepwise mechanism for the Strecker synthesis of racemic alanine from acetaldehyde.

What peptide remains after two sequential Edman degradations of the pentapeptide

How many standard amino acids are there?

Chymotrypsin is an enzyme which cleaves a peptide chain at the carboxyl groups of three aromatic amino acid residues. Name these three.

Draw the Fischer projection of L-valine at a pH of 2.

Show how a monosaccharide such as glucose can attach to a protein structure through the formation of an O-linked glycosidic bond with Ser. (Hint: This structure would be properly called an acetal.)

Which of the standard amino acids is achiral?

The reagent used in the determination of the N-terminal amino acid residue of a peptide is: