Sakaguchi’s reaction is specific for: (A) Tyrosine, (B) Proline, (C) Arginine, (D) Cysteine
Answer is C. Sakaguchi’s Test for Arginine : Free arginine or arginyl residues in proteins react with alpha-naphthol and alkaline hypobromite to give bright-red color. This is due to the guanidium group.
Reference: Vasudevan 7th  ed, pg 32