Biochemical Techniques and Instrumentation

5.3.2.4. Blocking

The membrane used for transfer has the ability to bind protein. As both the detection antibodies and the target are proteins, interactions between the membrane and the antibody used for detection of the target protein must be prevented. Blocking of non-specific binding is achieved by placing the membrane in a dilute solution (3-5%) of protein such as bovine serum albumin (BSA) or non-fat dry milk with a minute percentage of detergent such as Tween 20 or Triton X-100. This protein attaches to the membrane in all places where the target proteins have not attached. Thus, when the antibody is added, it will not attach other than on the binding sites of the specific target protein.