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1. (6 pts.) Shown below are the Ramachandran plots for three different pairs of

ID: 150133 • Letter: 1

Question

1. (6 pts.) Shown below are the Ramachandran plots for three different pairs of amino acids, X (the first amino acid of the dipeptide) and Y (the second amino acid of the peptide). The first (N-terminal) amino acid in EACH plot is the SAME. Panel A matches the image provided in your textbook and earlier on this exam. Given what you know about amino acids, fill in the blank by identifying the best candidate amino acid for the SECOND amino acid in each dipeptide. To earn full credit, you should write out the full name of the amino acid. Briefly (in 2-3 sentences) explain your reasoning Panel A: X-Y Panel B: X-? Panel C: X-?? (1 pt.) Panel B: X- (2 pts.) Reasoning: (1 pt.) Panel C: X- (2 pts.) Reasoning:

Explanation / Answer

In pannel B the second amino acid of the dipeptide is glycine.

Reasoning: The amino acid in the plot provided occupy 75% area of Ramachandran plot. Only glycine can do this due to absence of any steric hindrance.

In pannel C the second amino acid may be proline.

Reasoning: Due to presence of imino ring the side chain of proline is cyclic that doesn't allow the structure to rotate, hence occupy least area in Ramachandran plot.