Gel Electrophoresis on a Budget to Dye For: A Cost-Friendly Approach to Constructing and Using Electrophoresis Chambers (2010)

[ILLUSTRATION OMITTED] Gel electrophoresis is one of the most important tools used in molecular biology and has facilitated the entire field of genetic engineering by enabling the separation of nucleic acids and proteins. Though found primarily in Advanced Placement (AP) biology, this technique can also provide an engaging way to teach concepts across disciplines, including conductivity and molecular charge in chemistry and simple circuits and Ohm's law in physics. However, commercial electrophoresis kits can cost up to $800 for each setup, which is cost prohibitive for most classroom budgets. Teachers without electrophoresis chambers often have to rely on paper-and-pencil models of the activity (Nunley 1996). Even if classes do have the proper equipment, these special chambers are foreign to most students, who may be less likely to understand how they work as a result. The basic concepts behind gel electrophoresis, however, are simple enough for most high school students to understand. By conducting an electric current through an electrolyte buffer, charged molecules will migrate toward the oppositely charged terminal. When suspended within a polymer matrix, such as an agar gel, the molecules will move at different rates based on their size, mass, and charge. Therefore, an electrophoresis chamber need not be complicated and can be simply constructed using any container that can hold a gel and deliver a current across it. In this activity, students build their own electrophoresis chamber out of simple, inexpensive materials and use this apparatus to separate molecules of colored dyes. With careful shopping and savvy materials reuse, these chambers can be made for under $5 each. To develop these chambers, we evaluated the function of each component in a standard electrophoresis experiment and substituted readily available materials. Others have made simplified versions of gel electrophoresis chambers (Tan et al. 2007), but we sought to reduce the cost as much as possible and replace every component that would be unfamiliar to students. Not only does the low cost of each apparatus provide access to more classrooms, the process of creating and connecting their chambers helps students further their understanding of the principles behind this technique. Figure 1 Materials. Electrophoresis chamber: * small plastic box approximately 8 x 12 cm (e.g., empty micropipette-tip boxes or plastic food-storage containers) * two regular craft sticks * two narrow craft sticks (coffee stirrer type) * scissors * masking tape * two 12 cm pieces of stainless steel wire * two electrical leads with alligator clips * five 9V batteries (super heavy duty type work well) Gel and buffer: * water * baking soda * agar--agar powder (available from health food or Asian grocery stores) or agarose (available from chemical supply companies) * mat knife or razor blade Samples: * water * food coloring * glycerin (available from pharmacies) * needle-tip, disposable pipette * (optional) beaker of water for rinsing tips between samples Building the chamber The physical container for the electrophoresis chamber can be made of anything that will not conduct electricity (i.e., nonmetallic). In the spirit of reuse and as a nod to the high-end equipment we are recreating, we like to use the empty micropipette-tip boxes that are typically discarded after the disposable tips are used. These empty containers can often be obtained from a nearby college, biotechnology firm, or well-stocked AP biology class. The lids and bases, typically around 8 x 12 cm, are the perfect size for a student gel. If these are unavailable, any similarly sized rectangular container, such as a small, plastic food-storage container, can be used. The electric current is supplied via electrodes that can be made out of pieces of stainless steel wire and taped to each end of the box. …