Question

Sanger’s reagent is used for the identification of:
A.N-terminal of peptide chain
B.C-terminal of peptide chain
C.Side chain of amino acid
D.Number of amino acid in peptide chain

Answer 1

A reagent is a substance or compound added to a system to cause a chemical reaction, or added to test if a reaction occurs. Sanger's reagent is 1-Fluoro-2,4-dinitrobenzene (commonly called, dinitrofluorobenzene, DNFB or FDNB)

Complete step by step answer:
This process is a type of colorimetric analysis which means that we see a specific color to identify the product.
Sanger’s reagent reacts with the peptide chain and undergoes nucleophilic aromatic substitution (NAS) with the N-terminal amino group of a peptide or protein, resulting in a chemical tag on the terminal amino acid residue.
Then the product is hydrolyzed into individual amino acids, the peptide or protein's terminal amino acid can be identified by the specific wavelength of light absorbed (i.e., colorimetric analysis).
So we see that Sanger’s reagent reacts with the N-terminal of the amino acid.

So, the correct option is A.

Additional information:
A colorimeter is a device that is used in Colorimetry. It refers to a device which helps specific solutions to absorb a particular wavelength of light. The colorimeter is usually used to measure the concentration of a known solute in a given solution with the help of the Beer-Lambert law. There are two types of colorimeters — color densitometers, which measure the density of primary colors, and color photometers, which measure the color reflection and transmission.

Note:
In the molecule of a peptide, the amino acid residue on one end has an amine group on the alpha carbon. This amino acid residue is called the N-terminal of the peptide. The amino acid residue on the other end has a carboxylic acid group on the alpha carbon. This amino acid is called the C-terminal. In the above question we saw the reaction with the N-terminal.