English: Biuret reaction is used to confirm the presence of a peptide bond, hence it can be used for detecting peptides and proteins, as well as all other compounds containing at least two peptide groups. The name of the reaction originates from the compound biuret with the chemical formula HN(CONH2)2, obtained by condensation of two urea molecules. This compound gives a positive Biuret reaction. However, it is not used in the reaction itself.

To a protein solution, a solution of CuSO4 and NaOH are added. A violet color, which is a sign of a positive Biuret reaction, is obtained. The reaction that occurs is, in fact, the formation of a complex of copper with the protein. Thus, one of the possible mechanisms of the reaction includes coordination of copper with the –NH groups of the peptide bond through the lone electron pair from the nitrogen atom.

The experiment was performed by Prof. PhD Miha Bukleski. The planning of the experiment also included the Prof. Emeritus PhD Vladimir Petruševski, Prof. PhD Marina Stojanovska and the student Mihail Trajkov, Department of Chemistry, FNSM, Ss. Cyril and Methodius University, Skopje, Macedonia.