General chat about tween-20 as a WB block and wash - (Jan/18/2013 )
I was interested about the specific mechanism by which tween-20 works as a block and wash of western blot membranes, but unfortunately I couldn't find much on it except for one bulletin. This suggested the large size of tween-20 would make it useful for a block but also that it's size is due to it's large hydrophillic head so that doesn't quite make sense. As for it's ability to wash the membrane of antibodies, tween-20 has a low CMC and so may incorporate loosely bound antibodies into mixed micelles, while leaving bigger more strongly bound proteins on the membrane.
I dont know though... any ideas?
It doesn't function as a block at all - this is entirely down to the protein (e.g. milk powder) that you put in the block. The Tween acts largely as a surfactant to ensure that the whole surface of the membrane is coated and stays coated. It also acts as a stringency agent, stopping (mainly) non-specific binding by causing the antibodies to be in a partially denatured state.