Ninhydrin



Ninhydrin
IUPAC name Triketohydrindene hydrate
Identifiers
CAS number 485-47-2
Properties
Molecular formula C9H6O4
Molar mass 178.15 g/mol
Density 0.862 g/cm³
Melting point

250 °C

Hazards
R-phrases R22, R36, R37, R38
S-phrases S36
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Ninhydrin (triketohydrindene hydrate) is a chemical used to detect lysine residues) sloughed off in fingerprints react with ninhydrin.[1]

Uses

Ninhydrin can also be used to monitor deprotection in solid phase peptide synthesis (Kaiser Test).[2] 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.

Ninhydrin is also used in amino acid analysis of proteins: Most of the amino acids are chromatography.

A solution suspected of containing the amines, carbamates and also, after vigorous heating, amides.

Mechanism to generate the ninhydrin chromophore

Note that in order to generate the ninhydrin chromophore, the amine is condensed with a molecule of ninhydrin to give a Schiff base. Thus only ammonia and primary amines can proceed past this step. At this step, there must also be an alpha proton (H* in the diagram) for Schiff base transfer, so an amine adjacent to a tertiary carbon cannot be detected by the ninhydrin test. The reaction of ninhydrin with secondary amines gives an iminium salt, which is also coloured, and this is generally yellow-orange in color. for further information see: http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch27/ch27-3-3.html

See also

References

  1. ^ http://www.bergen.org/EST/Year5/fingerprint.htm
  2. ^ E. Kaiser, R. L. Colescott, C. D. Bossinger, P. I. Cook, Analytical Biochemistry 34 595 (1970)
 
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