Hopkin’s Cole Test- Definition, Principle, Procedure, Result, Uses


Proteins are one of the most important biomolecules in living organisms, as they perform various structural and functional roles. Proteins are composed of amino acids, which are the building blocks of proteins. Amino acids have different chemical properties and structures, which determine the characteristics of the proteins they form. One of the ways to study the properties and functions of proteins is to perform biochemical tests that can detect the presence or absence of specific amino acids or groups in proteins. These tests are based on the principle that different amino acids or groups react differently with certain reagents under specific conditions, resulting in a characteristic color change or precipitate formation.

One such test is the Hopkin’s Cole test, which is a specific test used for the detection of indole ring and thus, tryptophan in proteins. Tryptophan is one of the 20 standard amino acids that are found in proteins. It has a unique structure that contains an indole ring, which is a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. The indole ring is responsible for some of the biological activities of tryptophan, such as its role as a precursor for serotonin and melatonin, which are neurotransmitters involved in mood regulation and sleep cycle.

The Hopkin’s Cole test is also known as the glyoxylic acid test, as the reagent used in the test contains glyoxylic acid. The test was discovered by Frederick Gowland Hopkins and Sydney W. Cole in 1901 as a part of their work on the discovery of tryptophan. The test is one of the color reactions used for the detection of particular amino acids or proteins on the basis of the formation of a specific color. The test detects the indole ring that is found in tryptophan amino acid, which in turn helps in the identification of proteins containing tryptophan.

In this article, we will discuss the definition, history, principle, procedure, result, uses and limitations of Hopkin’s Cole test in detail.