ninhydrin test & biuret test?

Question

what is difference between ninhydrin test and biuret test.?

atleast 5 points

Answer 1

what do u mean by difference?
OK this is what i know

biuret test:
it is an universal test for proteins..all proteins answer this test.

here there is a formation of coloured co ordination complex between the unshared electron pairs of peptide nitrogen ,cupric ions and the oxygen of water.

the procedure involves-3ml of protein+3 drops pf 5% copper sulphate solution+3 or 4 drops pf 1% copper sulphate solution

u get a purple or pink colour as a positive test.

this test is positive when there are 2 or more peptide linkages..histidine is the only amino acid which answers this test


ninihydrin test:

when amino acids are heated with ninihydrin they are quantitatively deaminated and a bluish purple color appears due to formation of ruhemann's purple.

procedure involves addition of 1ml of protein solution with 2 drops of ninihydrin reagent and boil

a bluish purple color is obtained

proline and hydroxy proline give a yellow color

Answer 2

Ninhydrin Test

Answer 3

Biuret Test

Answer 4

Biuret's tests for amount of protein in a sample. Casein is a milk protein and will test positive, ie. violet color, since the reagent binds with peptide bonds. Ninhydrin is used to detect free amino groups, so unless you degrade the casein first, you will get a negative since the protein is bonded covalently (peptide bonds) and has only one free amino group at the N-terminus (disregarding any possible amino groups of the variable chain, ie R-group).

Answer 5

This Site Might Help You.

RE:
ninhydrin test & biuret test?
what is difference between ninhydrin test and biuret test.?

atleast 5 points

Answer 6

Well, Ninhydrin test is used to detect the presence of amino acids (individual amino acids not involved in the peptide bond) and Biuret test is performed to detect the presence of peptide bonds (between amino acids in proteins and smaller peptides).

The reason could be the fact that for Ruhemann's complex to form, amino acids should have free amino group and carboxyl groups.