Discontinuous Buffer System (Tris-CAPS) is used in semi-dry blotting systems, where different buffers are used at the anode and cathode. This is possible because in a semi-dry transfer, the buffer reservoirs are the filter paper on either side of the gel, which are independent. A discontinuous buffer system using a Tris-CAPS buffer can greatly increase the efficiency of protein transfer by semi-dry blotting.
In the discontinuous buffer system, methanol is included in the buffer on the membrane (anode) side of the blot assembly and SDS is used on the gel (cathode) side, taking advantage of the positive effects of each buffer component. This buffer system includes Tris-CAPS-Methanol (60 mM Tris, 40 mM CAPS, pH 9.6, plus 15% methanol) for the filter paper (anode side) and Tris-CAPS-SDS (60mM Tris, 40mM CAPS, pH 9.6 plus 0.1% SDS for the gel (cathode side).