Simon Fraser University
Engaging the World

Department of Physics

Demonstrations

5B10.XX Gel Electrophoresis

Concepts

Electric fields, diffusion

Overview

When dyes are in a gel in a strong electric field, their component molecules separate based on the electric force they feel and the ease of diffusion through the gel.

As a side note, it's also an interesting illustration of subtractive colour spaces used by inks and dyes.

Details

Equipment

  • [1] Electrophoresis tank
  • [1] Power supply with electrodes
  • [1] Transformer
  • [1] Gel tray with gel
  • [1] Lined transparency sheet
  • [1] Bottle of 1x TAE buffer
  • [1] 20 μL pipettor
  • [1] Box of pipette tips
  • [1] Set of 4 food colourings in Eppendorf tubes
  • [1] Overhead projector
  • [1] Waste beaker
  • [1] Free-standing projector screen
  • [1] Fuse box

Safety Equipment

  • [1] Safety goggles
  • [1] Box of disposable gloves.

Classroom Assembly

  1. Plug the power supply into the transformer.
  2. Use the electrodes to connect the power supply to the electrophoresis tank.
  3. Put the electrophoresis tank on the projector.
  4. Put the fuse box in the tank and focus the projector on the fuse box text. Remove the fuse box.
  5. Place the gel tray in the electrophoresis tank, with the transparency sheet underneath the tray. The wells in the gel should be closer to the negative electrode.
  6. Pour buffer into the tank until the gel is covered.
  7. Set up the projector screen.

Important Notes

  • Electric shock hazard! Do not touch the liquid when the demo is running! We usually run this demo with the electrophoresis tank lid removed. Otherwise, condensation can obscure the demo.

Script

  1. Put on your safety goggles and gloves.
  2. Inject the food colourings into the gel wells, going from left to right, in the order yellow, blue, red, green.
  3. Turn on the transformer and the power supply.
  4. Set the power supply to about 100 V, T = 0, and press run.
  5. Turn off the power supply and transformer when done.

 

Additional Resources

References

  • PIRA 5B10.XX

Disclaimer

  • Don't attempt this at home!

Last revised

  • 2023

Technicals

  • Buffer is TAE (tris, acetic acid, EDTA). Need 1 L of 1X TAE buffer.
  • Tank lid: need to remove electrodes before removing the lid. There are set screws holding the electrodes in place.
  • Gel: made using agarose and buffer. Use Teflon tape on the well mould to make structures 3 segments wide. Make sure the tape is taut to keep it well-wrapped during the gel formation. Use a small flat head screwdriver to push the tape through the prongs. Secure the gel tray in the tray holder and put in the well mould. Mix a 1% solution of agarose to buffer (0.5 g agarose to 50 mL of 1X buffer) in a small Erlenmeyer flask. Microwave until boiling for a couple of seconds. Use an oven mitt to swirl. Repeat until the agarose is fully dissolved and the solution is clear. Pour the agarose solution into the gel tray and let it cool until solid. Remove the tray from the holder, wrap it in plastic wrap, and refrigerate. It should be usable for a couple of days.
  • Cleanup: the buffer can go down the sink, and the gel can go in the garbage.

Related AV

Related demos

 

If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.