A certain polypeptide is shown by acid hydrolysis to contain only three amino acids: serine (Ser), alanine (Ala), and methionine (Met) with mole fractions of 1/2, 1/4, and 1/4, respectively. Enzymatic hydrolysis yields the following fragments: Ser-Ala; Ser-Met; Ala-Ser. Deduce the primary structure

Question

A certain polypeptide is shown by acid hydrolysis to contain only three amino acids: serine (Ser), alanine (Ala), and methionine (Met) with mole fractions of [latex]\frac{1}{2}, \frac{1}{4}[/latex], and [latex]\frac{ 1}{4}[/latex], respectively. Enzymatic hydrolysis yields the following fragments: Ser-Ala; Ser-Met; Ala-Ser. Deduce the primary structure of the polypeptide.

Accepted Answer

STRATEGY AND SOLUTION

Align the fragments vertically so that they overlap one another

Ser-Ala ¦ Ala-Ser ¦ Ser-Met
There are four amino acid units: Ser – Ala – Ser – Met
Since there are two serine units, one alanine unit, and one methionine unit, their mole fractions are
[latex]\frac{2}{4} = \frac{1}{2}[/latex] for serine [latex]\frac{1}{4}[/latex] for alanine [latex]\frac{1}{4}[/latex] for methionine

Question 23.10: A certain polypeptide is shown by acid hydrolysis to contain...

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