Gel Electrophoresis System

Overview

Gel electrophoresis sorts charged molecules by size. DNA, RNA, and many proteins carry a net charge, so when they sit in a gel and a voltage is applied across it, they migrate toward the opposite electrode; the gel acts as a molecular sieve, so small fragments thread through quickly and large ones lag behind. After a run, the lengths spread out into a ladder of bands. It is the everyday readout of molecular biology, checking a PCR product, sizing a digest, confirming a clone.

The system is two instruments that plug together: a buffer tank that holds the gel and the electrodes, and a high-voltage supply that creates the field. The gel itself is poured fresh for each run, which is why the casting hardware is part of the kit.

How it works

A gel is cast first. Molten agarose is poured into the Casting Set, a UV-transparent tray dammed at the ends, with a Well Comb suspended in it; as the gel sets, the comb's teeth leave a row of sample wells. The set gel, still in its tray, goes onto the Gel Platform inside the Buffer Tank, which is then filled with running buffer until the gel is submerged (hence "submarine" gels).

Each end of the tank carries a Platinum Electrode, a platinum wire chosen because it survives the electrolysis happening at the buffer surface. Samples mixed with a dense loading dye are pipetted into the wells, and the High-Voltage Power Supply is connected. The HV Control Board delivers a regulated voltage, constant voltage is the usual mode, and the molecules begin to march from the negative toward the positive electrode at a rate set by their size and charge. A tracking dye in the loading buffer shows how far the run has progressed.

High voltage sitting in an open salt-water tank is the obvious hazard, so the Safety Lid only completes the circuit through its Lid Interlock when seated, and the supply trips off if it detects no load. Current reaches the tank through the keyed Lead Set, and the operator watches voltage, current, and elapsed time on the supply's display before lifting the gel out to image the separated bands.