Ninhydrin

Ninhydrin is a chemical used to detect ammonia or primary amines. When reacting with these free amines, a deep blue or purple color is evolved. Ninhydrin is most commonly used to detect fingerprints, as amines left over from peptides and proteins (terminal amines or lysine residues) sloughed off in fingerprints react with ninhydrin.

Related Topics:
Ammonia - Amine - Fingerprint - Terminal amine - Lysine

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Ninhydrin can also be used to monitor deprotection in solid phase peptide synthesis. When the growing peptide chain is deprotected, a ninhydrin test yields blue. If the next peptide residue is coupled then the test is colorless or yellow.

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Ninhydrin is also used in amino acid analysis of proteins: All of the amino acids are hydrolyzed and reacted with ninhydrin; they are then quantified colorimetrically after separation by chromatography.

Related Topics:
Hydrolyzed - Chromatography

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A solution suspected of containing the ammonium ion can be tested by ninhydrin by dotting it onto a solid support (such as silica gel); treatment with ninhydrin should result in a dramatic purple color if the solution contains this species.

Related Topics:
Ammonium - Silica gel

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