Mini-PROTEAN 3 Multi-Casting Chamber From Bio-Rad

SDS-PAGE (Sodium Dodecyl Sulphate-PolyAcylamide Gel Electrophoresis) is a technique for separating proteins according to their size. Many of us have this experience: for the sake of convenience, we got an offer of a starting combo – 5 sets of glass plates, a pair of combs, two clamps, one casting stand for two gels at a time, and one gel releaser. They had served you well, until you got to work with more cells, more treatments, and more samples. The next problem is gel solution leakage that leaves you two gels of different separating gel length – you either accept it or discard it and start over again. When I first learned how to prepare a SDS-PAGE, the demonstrator repeatedly emphasized on how dangerous the acrylamide solution is, and warned us to handle the glass plates with extreme care, since even small cracks on the corners can cause gel solution leakage. From the safety data sheet of acrylamide, he is right. However, to avoid protein residue carry-over between different runs, it’s necessary to wash the glass plates thoroughly after each run, which inevitably speeds up the wearing process.

Now the situation turns into: you have many more samples than two gels can hold, and 5 sets of glass plates which are a bit worn out. I would suggest Bio-Rad’s Mini-PROTEAN 3 Multi-Casting Chamber here. At first sight, you may wonder why some plastic sheets, a few acrylic blocks, a casting chamber, a sealing plate, a tapered luer fitting and a stopcock valve could cost you so much. Well, the cost is for its design. Decide on the number of identical gels you need. Set up sandwiches of plastic separation sheet, spacer glass plate and short glass plate in the casting chamber as the manual instructs. Fill the remaining space with the acrylic blocks or short plates or separation sheets as instructed. Then secure the casting chamber with the sealing plate and tighten the screws. You are now ready to cast 12 identical gels using just a compact space of 10 cm x 10 cm x 16 cm.

Prepare your gel solution as usual. In my experience, for 12 x 0.75 mm gels, I usually prepare ~60 ml of separating gel solution and 24 ml of stacking gel solution. Do not add TEMED and APS until you are about to pour the solution. Attach the stopcock valve and ensure it’s in the ‘close’ position. When you are ready, combine TEMED and APS to the separating gel solution, briefly mix and transfer the solution to the casting chamber with a pipet. Then you will see the beauty of its design – the groove on the bottom of the casting chamber equilibrates gel solution to each gel sandwich. Stop when the gel solution reaches your desired gel height, which can be monitored through the transparent sealing plate. Overlay the separating gel with alcohol and wait for the gel to set. Then remove the overlaying alcohol and rinse with distilled water. For the stacking gel, I would recommend one thing: prepare the stacking gels one at a time – i.e. from the 24 ml solution, take 2 ml and add TEMED + APS, apply to one gel sandwich, insert the comb, and then take another 2 ml solution. If you combine the 24 ml solution to TEMED + APS at once, you need to be really fast to insert 12 combs (sorry, I can’t do that), and you may not have time to check if there are any bubbles trapped.

Since the sets of glass plates are contained inside the chamber, even glasses with a crack at the corner can be used and there will be no leakage of gel solution. After the gels are set, disassemble the casting camber and trim off excessive gel bits from the gel sandwiches. Store them or use them right away. Then roll up your sleeves and do the washings.