*This protocol is applicable to Bio-Rad Mini-PROTEAN® Tetra, Mini-PROTEAN II®, and Mini-PROTEAN® 3 electrophoresis systems.
Figure 1. The rubber gasket in the Bio-Rad electrophoresis unit needs to be flipped before placing the mPAGE™ gel.
Figure 2.Left: Incorrect orientation of Bio-Rad gasket for use with mPAGE™ gels. Right: Correct orientation of Bio-Rad gasket for use with mPAGE™ gels.
There are two buffers that can be used as running buffers for SDS-PAGE gels: MES and MOPS. MES has a lower pKa than MOPS, which enables the gel to run faster. MES buffer gives better separation of proteins at lower molecular weights, while MOPS buffer provides better separation at higher molecular weights (Figure 3).
Figure 3. Selection of MES (left image) vs. MOPS (right image) running buffer for mPAGE™ protein gel electrophoresis, based on protein size and percent acrylamide gel. Protein size for corresponding bands indicated in kDa. Smaller proteins are resolved more efficiently with MES running buffer; larger proteins are resolved more efficiently with MOPS running buffer.
Figure 4. Improper and proper pipette angle for loading samples into mPAGE™ pre-cast gels.