NIV 迫 Experimental principle 2. Biuret test: The compound with polypeptide skeleton can react with Cu2+ under basic condition which will form purple complex A"9人° Protein or polypeptide urple complex2. Biuret test ：The compound with polypeptide skeleton can react with Cu2+ under basic condition, which will form purple complex. Protein or polypeptide Purple complex Experimental principle