<prompt> Which among the following when reacted with diazotized sulfanilic acid under alkaline conditions, a red color is formed?TyrosineArginineHistidineCysteine  <response>: Paulys test: Paulys test is used for detecting the presence of histidine in proteins. When proteins containing histidine react with diazotized sulfanilic acid under alkaline conditions, a red color is formed by a coupling reaction. The same reagent will give an orange colored product with the phenol group of tyrosine TESTREACTION AMINO ACID Biuret Reaction Two peptide linkages Ninhydrin Reaction Alpha- amino acids Xanthoproteic Reaction Benzene ring of aromatic amino acids Millons Reaction Folin-Ciocalteus Test Phenolic group Tyrosine Hopkins-Cole Reaction Indole ring Tryptophan Sakaguchi Reaction Guanidine group Arginine Nitroprusside Reaction Sulfur Test Sulfhydryl groups Cysteine Paulys Test Imidazole ring Histidine Reference: Harpers illustrated biochemistry 30th edition 