Pauly’s Test- Definition, Principle, Procedure, Result, Uses


Proteins are essential biomolecules that perform various functions in living organisms. Proteins are composed of amino acids, which are the building blocks of proteins. Amino acids have different chemical properties and structures that determine their role and function in proteins. Some amino acids have aromatic groups, such as phenol or imidazole, that can react with certain reagents and produce characteristic colors. These reactions can be used to detect and identify these amino acids in proteins.

One such reaction is Pauly’s test, which is a biochemical test for the detection of tyrosine and histidine in proteins. Tyrosine and histidine are two amino acids that have aromatic groups that can undergo coupling with diazonium salts. Diazonium salts are compounds that have a nitrogen-nitrogen double bond attached to an aromatic ring. They are highly reactive and can form colored complexes with other aromatic compounds.

Pauly’s test is named after the German chemist Hermann Pauly, who discovered the test in 1894. He used sulphanilic acid as the source of diazonium salt and observed that it reacted with tyrosine and histidine to produce red-colored compounds. He also noticed that the color intensity varied depending on the pH of the solution. Pauly’s test is a specific test for proteins containing tyrosine and histidine as the reagent undergoes diazotization with aromatic groups. The reaction is performed under cold conditions as the diazonium compound can only form at low temperatures.

Pauly’s test is a simple and rapid method to detect the presence of tyrosine and histidine in proteins. It can also be used to differentiate between these two amino acids from other amino acids that do not react with diazonium salts. The test can be performed in a test tube using a few reagents and materials. The result of the test is indicated by the appearance or absence of a red-colored solution.

In this article, we will discuss the objectives, principle, procedure, result, uses, and limitations of Pauly’s test in detail. We will also explain the reaction involved in Pauly’s test and how it produces the characteristic color change. We hope that this article will help you understand Pauly’s test better and appreciate its importance in biochemistry.