18. Complete hydrolysis of a nonapeptide gave 3 ala, 2 phe, 2 asp, gly, and ser.

Question

18. Complete hydrolysis of a nonapeptide gave 3 ala, 2 phe, 2 asp, gly, and ser. Reaction of the nonapeptide with Sanger's reagent (1-fluoro-2,4-dinitrobenzene) followed by hydrolysis gave N-(2,4-dinitrophenyl) alanine. Partial hydrolysis of the nonapeptide gave the following fragments: gly-ala-phe ala-asp-gly-ala phe-ser-ala ser-ala-phe-asp ?? Which one of the following is the nonapeptide's pripary structure? ) ala-asp-gly-ala-asp-ala-phe-sor-phe C (ala-asp-gly-ala-phe-ser-ala-phe-b B) ala-phe-asp-gly-ala-asp-ser-phe-ala D) gly-ala-phe-ser-ala-phe-asp-asp-ala

Explanation / Answer

Since reaction with Sanger's reagent followed by hydrolysis gave N-(2,4-dinitrophenyl) alanine, the first amino acid has to be alanine. From the fragments obtained from partial hydrolysis, we can arrange the fragments to get the nine amino acid long peptide chain.

ala-asp-gly-ala

gly-ala-phe

phe-ser-ala

ser-ala-phe-asp

So the correct sequence of peptide is "ala-asp-gly-ala-phe-ser-ala-phe-asp"

Kindly rate if this was helpfu.

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