biuret test

The biuret test is a chemical test for proteins and polypeptides.

The biuret test is a chemical test used for detecting the presence of peptide bonds.

Not all biuret tests require the biuret reagent.

The method combines the reactions of copper ions with the peptide bonds under alkaline conditions (the Biuret test) with the oxidation of aromatic protein residues.

Two major types of the biuret test are commonly applied in modern colorimetric analysis of peptides: the Bicinchoninic Acid (BCA) assay and the Modified Lowry assay.

The BCA protein assay increases the sensitivity of the biuret test by a factor of around 100, and gives the important benefit of compatibility with samples that contain up to 5% surfactants.

Millon's test is not specific for proteins (it actually detects phenolic compounds), and so must be confirmed by other tests for proteins such as the biuret test and the ninhydrin reaction.