proteins test

• to test for proteins you use a biuret test
• • if protein is present, the colour changes from light blue to lilac
  • you may find reagents separately as Biuret A (sodium hydroxide) and Biuret B (copper sulphate)
  • you add Biuret A first then add Biuret B
  • colour is formed by a complex between the nitrogen atoms in a peptide chain and Cu 2+ ions, which is why this test actually tests for presence of peptide bonds