VPB 112: General Veterinary Biochemistry (1+1)

XANTHOPROTEIC TEST

• This is for identifying proteins containing aromatic amino acids.

Principle

• Amino acids with an aromatic ring (tyrosine, tryptophan and phenyl alanine) form yellow nitro derivatives on heating with Conc. HNO₃. The salts of these derivatives are orange in color.

Procedure

• To 1 mL of test solution add 1 mL of Conc. HNO_3.
• A white precipitate formed upon boiling for half a minute turns into a lemon yellow.
• Cool under tap water and add 1 mL of 40% NaOH.The yellow color changes to orange.
• (Repeat the test with 2% phenol solution and compare the result).

Experiment	Observation	Inference

Experiment	Observation	Inference

Experiment	Observation	Inference