# 121. Ксантопротеинска реакција

The xanthoproteic reaction is used to detect the presence of proteins that contain aromatic amino acids in their structure (e.g., tyrosine, tryptophan).

To a protein solution, concentrated nitric acid is added, and the test tube is heated. Then, concentrated ammonium hydroxide (or sodium hydroxide) solution is added to the test tube, and the heating is continued. A yellow-orange product is obtained, indicating a positive reaction.

The reaction is based on the nitration of the aromatic ring of the amino acid with concentrated nitric acid, resulting in the formation of nitro compounds with a characteristic yellow color. By adding ammonium hydroxide, the color changes to orange due to the formation of a salt of the tautomeric form of the nitro compound.

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.

- Kind: Short
- Year: 2024
- Runtime: 1 min
- By: Deni Ingilizovski
- Genres: Science
- Archive: [Wikimedia Commons](https://commons.wikimedia.org/wiki/File:121._%D0%9A%D1%81%D0%B0%D0%BD%D1%82%D0%BE%D0%BF%D1%80%D0%BE%D1%82%D0%B5%D0%B8%D0%BD%D1%81%D0%BA%D0%B0_%D1%80%D0%B5%D0%B0%D0%BA%D1%86%D0%B8%D1%98%D0%B0.webm)
- Licence or status: [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0) (as the archive states it)
- Credit: Deni Ingilizovski
- Who can watch: Tweens profiles and older (the archive gives no rating; placed by Invisible Network from its collection and subjects)

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