#ninhydrin

Chemicals which are used to detect fingerprints.

1.) Ninhydrin is most commonly used to detect fingerprints, as the terminal amines of lysine residues in peptides and proteins sloughed off in fingerprints react with ninhydrin. It is a white solid which is soluble in ethanol and acetone at room temperature.

2.) Zinc Chloride is also used by forensic laboratories for enhanced finger print detection.

3.) 1,8-Diazafluoren-9-one, also known as DFO, is a chemical that is used to find fingerprints on porous surfaces. It makes fingerprints glow when they are lit by blue-green light. DFO reacts with amino acids present in the fingerprint to form highly fluorescent derivatives.

4.) Nonpolar Ninhydrin is used to detect fingerprints because it reacts with amino acids from the proteins in skin cells transferred to the surface by the individual leaving the fingerprint.

5.) 1,2-Indanedione is the result of the search for a low cost substitute for DFO. Like DFO and ninhydrin, LV508 reacts to amino acid residues on porous surfaces, but it rarely produces visible prints. Developed prints do produce strong fluorescence when exposed to comparable alternate light source illumination.

6.) 5-Methylthioninhydrin (5-MTN) is a reagent for fingerprints that combines the favorable characteristics of ninhydrin (strong color) and those of DFO and 1,2-IND (strong fluorescence). 5-MTN-developed fingerprints have a stronger color than those developed with regular ninhydrin. 

7.) 2-Isononylninhydrin (INON, Thermanin) is used to detect fingerprints.

In solid phase peptide synthesis Kaiser Test is a quite important thing when you need to detect free N terminus at the end of your amino acid chain. The chain is linked via its C-terminus to the solid support, with the N-terminus extending off it. When that nitrogen is deprotected, a ninhydrin test yields blue. Amino-acid residues are attached with their N-terminus protected, so if the next residue has been successfully coupled onto the chain, the test gives a colorless or yellow result.

The only problem is when the ninhydrin solution accidentally goes through your gloves, gets on your skin and reacts with your amino acids, mainly with free N terminal of lysine (first pics) and turns your skin purple.