Question 18.4: Drawing Dipeptides Draw the structure of the dipeptide Ala-G......
Drawing Dipeptides
Draw the structure of the dipeptide Ala-Gly.
ANALYSIS You need the names and structures of the two amino acids. Since ala -nine is named first, it is the amino-terminal and glycine is the carboxyl-terminal. Ala-Gly must have a peptide bond between the —COO^- on alanine and the –NH_3^+ on glycine.
The structures of alanine and glycine, and the structure of the Ala-Gly dipeptide are
\begin{matrix} \underset{\mid\mid}{O}\\ H_3\overset{+}{N} —\underset{\mid}{C}H —C—O^-\\CH_3\\Alanine (Ala)\end{matrix} \begin{matrix} \underset{\mid\mid}{O}\\ H_3\overset{+}{N} —CH_2 —C—O^-\\ \\Glycine (Gly)\end{matrix}
\begin{matrix} \underset{\mid\mid}{O} \boxed{Peptide bond} \underset{\mid\mid}{O}\\ H_3\overset{+}{N} — \underset{\mid}{C}H — C\overset{ \swarrow }{—}NH — CH_2 — C—O^-\\CH_3 \end{matrix}
Ala-Gly