Ninhydrin test is used for ?
Bile salts
Amino acids
Nucleic acid
Lipids
Ans. is 'b' i.e., Amino acids Impoant chemical reactions of amino acids Following are some impoant chemical reactions. A. Reaction used to determine amino acid sequence in polypeptide chain : - Generally, amino terminal (N-terminal) of amino acid is tagged with some reagent. It is split off by hydrolysis and tagged amino acid is identified. The reaction is, then, repeated with new N-terminal of subsequent amino acid and so on. The two reactions are used for identification of amino acid sequence : ? Sanger's reaction : - Uses Sanger's reagent ( 1 -fluoro-2,4-dinitrobenzene) to tag amino terminal. Edman's reaction : - Uses Edman's reagent (phenylisothiocyanate) to tag amino terminal. B. Reaction used to identification of individual or group of amino acids : - These reactions are frequently used for qualitative detection and quantitative measurement of various amino acids. Ninhydrin tese : - All a-amino acids. Xanthophoretic reaction : - Aromatic amino acidse (Tyrosine, tryptophan, phenylalanine). Millan's teste (Millon-Nasse reaction) : - Tyrosinedeg (phenol group of tyrosine). Therefore millon's test is positive in tyrosinosisdeg. Aldehyde test : - Tryptophan (indole ring) Hopkins-tole reaction : - Tryptophan (indole ring) Sakaguch's reaction : - Arginine (guanidinium group of arginine). Sulphur test : - Cysteine (sulphydryl group) Nitroprusside test : - Cysteine (sulphydryl group) Pauly's test : - Histidine (imidazole group) Biuret reaction : - Peptide bond Diazo reaction Q (Pauli's) : - Histidine or tyrosine.