Diapositiva 1

Amino Acids

Esguerra, ImarieFernandez, Aldrin

Fajutagana, ClariceGamboa, Lois

Ninhydrin Test

The Ninhydrin Test is a test for amino acids and proteins with a free -NH2group. When such an -NH2group reacts with ninhydrin, a purple-blue complex is formed (Ruhemann's purple) .

Ninhydrin (triketohydrindene hydrate) is an oxidating agentwhich leads to the oxidative deamination of alpha-amino groups. It is very important for the detection and the quantitative analysis of amino acids. Ninhydrin also reacts with primary amines however the formation of carbon dioxide is quite diagnostic for amino acids.When reacting with free amines from the amino acid, blue or purple color is produced. Most of the amino acids are hydrolyzed and reacted with ninhydrin except proline.

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Results

Amino AcidColor ResultsAlanine (Ala)Clear solution (no change)Histidine (His)Clear to Purple solutionAspartic Acid (Asp)Clear solution (no change)Tyrosine (Tyr)Clear solution (no change)

Xanthoproteic Test

Aromatic amino acids, such as Phenylalanine, tyrosine and tryptophan, respond to this test. In the presence of concentrated nitric acid, the aromatic phenyl ring is nitrated to give yellow colored nitro-derivatives. At alkaline pH, the color changes to orange due to the ionization of the phenolic group.

Results

Amino AcidColor ResultsAlanine (Ala)Clear solution (no change)Histidine (His)Clear solution (no change)Aspartic Acid (Asp)Clear solution (no change)Tyrosine (Tyr)Clear to Light Yellow solution