Blocking
The membrane has the ability to bind to proteins in this case both the target and
antibodies are proteins and so there could be some unwanted binding.
Blocking of non-specific binding is achieved by placing the membrane in a dilute
solution of protein – typically Bovine serum albumin (BSA) with a minute percentage
of detergent such as tween 20.
The protein in the dilute solution attaches to the membrane in all places where the
target proteins have not attached. Thus, when the antibody is added, there is no room on
the membrane for it to attach other than on the binding sites of the specific target
protein.