Millon's reagent is an analytical reagent used to detect the presence of soluble proteins. A few drops of the reagent are added to the test solution, which is then heated gently. A reddish-brown coloration or precipitate indicates the presence of tyrosine residue which occur in nearly all proteins.[1] The test was developed by the French chemist Auguste Nicolas Eugene Millon.
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The reagent is made by dissolving metallic mercury in nitric acid and diluting with water, forming mercuric nitrate (Hg[NO3]2).[2] In the test, the phenol group in the side chain of tyrosine gets nitrated, and that product then complexes with Hg(I) or Hg(II) ions to give a red colored precipitate. Millon's test is not specific for proteins; it also gives a positive test for other compounds containing the phenol functional group. Therefore, the biuret test or the ninhydrin reaction are used along with it to confirm the presence of proteins.
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editReferences
edit- ^ Walsh, Edward O. (1961). An Introduction to Biochemistry. London: The English Universities Press; Hodder & Stoughton. pp. 406–407. OCLC 421450365. Archived from the original on 2022-05-16. Retrieved 2022-05-16.
- ^ "Millon's reagent, for the detection of Tyrosine, Thermo Scientific | Fisher Scientific". www.fishersci.com. Archived from the original on 16 May 2022. Retrieved 16 May 2022.