Exam 24: Amino Acids, Peptides, and Proteins

The H-bonds formed in the tertiary structure of proteins can be differentiated from those formed in secondary structures. What is the major distinguishing factor?

What is the major end product of the following reaction series?

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

Disulfide linkages can form between:

Provide the single letter code for the following peptide Arg-Phe-Tyr-Cys-Asp-Trp-Gln-Ala-Glu-Glu-His-Lys

What name is given to a protein infectious agent that is thought to promote misfolding and polymerization of normal protein molecules and that is believed to cause Creutzfeldt-Jakob Disease?

Draw structures for the forms of glycine present in basic, neutral, and acidic solutions.

Provide the structure of the major organic product which results when L-phenylalanine is treated with a large excess of PhCH₂OH and gaseous HCl.

The primary structure of a protein refers to:

Which of the following amino acids has its isoelectric point at the lowest pH?

Provide a reasonable synthesis of PhCH₂CH(NH₃⁺)CO₂H from BrCH(CO₂CH₂CH₃)₂.

Before Edman degradation, Fredrick Sanger developed the first method to analyze the N-terminal amino acid of a protein using 2,4-dinitrofluorobenzene in the following reaction. Propose a mechanism for this reaction.

Provide the structure of L-aspartic acid at pH 12.0.

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

Draw the structure of Lys-Phe-Leu at biological pH.

Which amino acid has an amide group in its side chain?

Most naturally occurring amino acids are L-amino acids. Does this mean they are levorotatory? Explain.

Which amino acid has a phenol in its side chain?

Which of the following amino acids has its isoelectric point at the highest pH?

When the structure of a small dipeptide was examined using NMR, it was observed that the carbonyl oxygen atoms in the backbone structure are nearly always trans with respect to the H atoms on the amide nitrogens. Explain this observation and include diagrams.