Fig. 1
Visualizing reactions between two different optically absorbing reagent species using band-collision gel electrophoresis (BCGE). a A gel having two wells per lane is cast and transferred into a transparent horizontal gel electrophoresis chamber filled with a buffer solution at a desired pH. Pt-wires near the ends of the chamber, designated by black (−) and red ( + ), are connected to a power supply (not shown). Each well is loaded with a different reagent species, and the power supply, which generates an electric field E that lies along the x-direction, is turned on at time t = 0. A light box underneath the chamber provides uniform transmission illumination of white visible light, and time-lapse images are captured by an overhead camera with a lens selected to minimize spatial distortion. b Overhead view depicting the center locations x1(t) and x2(t) of propagating bands of reagent species 1 (blue band) and 2 (purple band), respectively, in a lane at time t; both x1 and x2 are referenced relative to the well centered at x = 0. Reagent species 1 and 2 were initially loaded into the wells centered at x = 0 and x = L, respectively. Here, the electrophoretic mobilities of reagent species 1 and 2 have μe,1 > 0 and μe,2 < 0, respectively. c–e Each panel shows the evolution of bands in a single lane containing two wells during BCGE for different μe,1 and μe,2 (see the Methods section): (left) at time t = 0 when E is turned on, (middle) at some time later t < t* before band collision, and (right) full band collision at t = t*, yielding band-collision location x*. c Counter-propagating BCGE: μe,1 > 0 and μe,2 < 0, so band collision always occurs at x* between the wells. d Uni-propagating BCGE: μe,1 = 0 (as shown) or μe,2 = 0, so the band of charged reagent species collides with the stationary band of uncharged reagent species in its well. e Co-propagating BCGE: both μe,1 and μe,2 have the same sign (<0 as shown) but μe,1 ≠μe,2, so band collision occurs at x* outside the region between the wells
