Mini-PROTEAN II Multiscreen Apparatus From Bio-Rad

As illustrated by its name, Bio-Rad Mini-PROTEAN II Multiscreen Apparatus is designed for screening. More specifically, it’s for screening antibodies and sera via Western blot. From its appearance, one can imagine how it works. It consists of a base which can hold two 7 cm x 8 cm membranes, each side has a gasket (which provides a leakproof seal and prevent cross-contamination between samples), and a sample template (each provides twenty 2.5 mm x 5.2 cm x 5 mm channels). First, cast a gel with an IPG well comb. Then resolve the protein marker (in the small well) and your sample (in the large well). Just imagine the same whole set up for your Western blot, except replacing the container for primary antibody incubation with the multiscreen apparatus: after transferring the proteins from the SDS-PAGE to the membrane, block the membrane with non-fat milk or BSA as usual. Then, clamp the membrane between the gasket and the sample template. Note that the four screws must be tightened in a random order so as to secure a leakproof seal. For each channel, prepare 600 ul of antibody. To avoid forming bubbles inside the channel, I usually tilt the whole apparatus a little and pipet the antibody through the lower hole carefully. Then this one is optional: I wrap the holes with saran wrap and put the whole apparatus on a orbital shaker – at least I feel more secure, but it’s up to you. After the primary antibody incubation, tilt the apparatus a little again and suck up the antibody one by one with a pipet before dissembling the apparatus. Now, the membrane will look like a rippled potato chip. That’s a good sign, telling you that there is no inter-channel leakage. Then, continue with subsequent washing steps, secondary antibody incubation, and signal development.

The manufacturer claims that ‘using the Mini-PROTEAN II multiscreen apparatus, you can quickly and efficiently screen up to 40 different antibodies or sera without having to cut the Western blot into individual strips’. Well, it has provided 40 channels in total (2 x 20 channels), but using the IPG well comb the length of the well can at most reach the 17th channel for one membrane (i.e. total = 2 x 17 = 34 samples). Or you may give up the protein marker so as to fully utilize the length of the mini-protein gel.

Your boss may not want to admit it, but all of us know that there could be run-to-run differences between two blots even though the same sample was loaded. Using this apparatus, precise side-by-side comparisons result. This screening approach maximizes the number of antibodies and/or concentrations to be tested while minimizing the amount of each antibody needed. This apparatus is for labs dedicated to developing maximum utility of their antibodies.