Band-collision gel electrophoresis (BCGE) for visualizing molecular and colloidal interactions

Electrophoretic mobility shift assays (EMSAs) are widely used to study binding interactions between different molecular species loaded into a single well within an electrophoresis gel. However, shift assays can explore only a subset of reaction possibilities that would otherwise be accessible if separate bands of reagent species were instead collisionally reacted. We fabricate a gel with two or more wells within a single lane and load these wells with different reagent species. By applying an electric field, we produce collisional reactions between propagating pulse-like bands of these species and record the images optically. We observe cases where bands pass through one another undisturbed, while in other cases, we observe complexing and precipitation, indicating strong attractive interactions. This band-collision gel electrophoresis (BCGE) approach is generalizable to a variety of reaction types, such as acid-base, ligand exchange, and redox, as well as to colloidal species in passivated large-pore gels.