We currently use Bio-Rad’s Mini-Protean III and Mini Trans-blot cell for running protein gels and for Western blotting. These two products can be purchased together and are designed to share the same components. The Mini-Protean III Cell is vastly improved from previous protein gel systems made by Bio-Rad. Almost everything needed (except chemicals, buffers and a power supply) to cast and run a protein gel is included. With the addition of the Mini Trans-blot, you have everything needed (except buffers and membranes) to transfer proteins to nitrocellulose for Western blotting.
I used to have considerable problems with gels leaking during casting with the older Bio-Rad systems that used the black spacers to separate the short and tall glass plates. In this system, the spacers are part of the taller plate (called the spacer plate) so only the two pieces of glass are needed to form the gel sandwich. The two pieces of glass are then inserted into a casting frame that rests on the benchtop. This frame ensures the glass plates are even and tightly secured before they are placed in the casting stand where the gel will be poured. I find it best to let everything rest on the bench and while pushing down evenly on the top of the glass pieces with your fingers, snap the green casting frame shut with your thumbs. The casting stand then secures the frame and plates against a rubber gasket in order to create a seal so that the gel solution will not leak during casting. Once everything is assembled, the gel is ready to be poured as usual. To level the separating portion of the gel before it polymerizes, we insert a syringe filled with water between the two glass plates to drip water on top of the gel solution – this works extremely well. Using this improved design, I seldom have a gel leak while being poured, which is something I couldn’t say for the previous system.
The running apparatus has been improved from previous models as well, so you don’t get buffer leaking from the interior chamber into the exterior reservoir. This ensures the gels run properly and that they do not stop prematurely. If the buffer in the outside compartment is not high enough and the apparatus leaks, the buffer in the inside chamber can drain below the shorter piece of glass and stop the gel from running. Of course, if the gel apparatus has not been assembled correctly and the buffer does leak, you can always fill the outside compartment with buffer to the same level as the inside compartment. This will prevent the buffer from the inside compartment from draining too low.
After the gel is finished running, setting up the transfer is fast and easy. The Mini Trans-blot includes everything but the nitrocellulose membrane needed to setup the transfer. The transfer cassette is placed with the black side down and the transfer is assembled using the provided filter pads and filter paper in the following order: filter pad, filter paper, gel, membrane, filter paper, filter pad. If you run out of the filter paper pieces that come with the Trans-blot system, you can just cut up pieces of Whatman filter paper and these work just fine. Once the gel is finished running, it takes less than 15-20 minutes to set up the transfer apparatus.
There are no major disadvantages with these two products which are integrated very nicely. In time, however, some of the pieces give out and can be expensive to replace. We have had the hinges on the transfer cassettes break after a decent amount of use and in the past, we have had to purchase a whole new transfer cassette as we were told they don’t sell just the hinge. After speaking to the local sales representative, he told me you can indeed buy just the hinge, you just need to know the catalog number. I have not confirmed this myself as we have not had one break since then. When the next one breaks, I guess we will find out. The shorter glass plates also break after some use, but this is expected. Besides these little concerns, we are very happy with Bio-Rad’s Mini-Protean III Gel System with the integrated Mini Trans-blot cell for Western blotting.