Question

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? A) ala-asp-gly-ala-asp-ala-phe-sor-phe B) ala-asp-gly-ala-phe-ser-ala-phe-b C) ala-phe-asp-gly-ala-asp-ser-phe-ala D) gly-ala-phe-ser-ala-phe-asp-asp-ala

Answer 1

The primary structure of the nonapeptide is gly-ala-phe-ser-ala-phe-asp-asp-ala, determined by the amino acid composition, Sanger's reagent labeling, and partial hydrolysis results.

Step-by-step explanation:

The primary structure of proteins is simply the sequence in which amino acids are connected by peptide bonds. In your question regarding the primary structure of the nonapeptide, we need to determine the correct sequence of amino acids based on the given information. You provided data from a complete hydrolysis, reaction with Sanger's reagent, and results from partial hydrolysis. Sanger's reagent specifically labels the N-terminal amino acid of the peptide, which in this case is alanine. By analyzing the partial hydrolysis results and the amino acid composition of the nonapeptide, we can deduce the sequence. Considering the consistency with the partial fragments and Sanger's reagent labeling, the correct primary structure of the nonapeptide is gly-ala-phe-ser-ala-phe-asp-asp-ala. This takes into account the counts of each amino acid, the N-terminal label, and the partial hydrolysis results, putting the unique amino acid, glycine, at the N-terminus as indicated by the reaction with Sanger's reagent.

Answer 2

Alanine is obtained as the first amino acid, taking into account that the reaction with the Sanger reagent hydrolyzes N- (2,4-dinitrophenyl) alanine. thus with the fragments of the partial hydrolysis they are organized to create a polypetidic chain

ala-asp-gly-ala

gly-ala-phe

phe-be-wing

be-wing-phe-asp

We obtain that the correct sequence of the peptide is "ala-asp-gly-ala-phe-ser-ala-phe-asp"