A simple minigel system is recommended, one that takes 3"h x 4"w plates (lantern slides). Major suppliers are not the best source, in fact, apparatus can be easily "homemade." Idea Scientific has them for around $200. Our source is Custom Crafting, (713) 561-0471 (Sam Lee), who supplies them for about $120, and also makes the well former and spacer sets. The minigel system consists of a bottom chamber with anode, a top chamber with slot for the gel cassette, and a top with cathode that fits into the upper chamber. Cassettes are clipped in place with binder clips and the slot sealed with 2% agarose. The chamber should be designed so that it cannot be connected to power with the lid off.
For greater safety, many labs use pre-cast gels. Commercially available gel systems may be preferable, although they can be expensive.
The input side of a vacuum pump should be connected to the arm of a 500 ml sidearm flask. Cut ends off of two suitable automatic pipettor tips or use suitable hard plastic tubing to make two connectors that can be shoved through a two-hole stopper that fits into the flask (#7). Connect two pieces of flexible tubing to the connectors and make a similar connection at the other end of the tubing, to a one-hole stopper that fits a 125 ml erlenmeyer flask (#5). The 500 ml flask should be secured to a ringstand clamp to avoid disaster.
To use, turn on the pump and place
each #5 stopper into a 125 ml flask.
Both flasks may contain acrylamide,
or one may be used simply as a "dummy"
flask to maintain vacuum. De-gas for
a suitable amount of time (5 min. is
usually enough), then pop off the stopper
before turning off the pump, to avoid
drawing oil-saturated air into the 125
For a photographic negative a stand-mounted SLR camera with macro lens and green filter is recommended. Recommended film is Kodak Technical Pan (B & W), specially designed for high resolution scientific applications. A gel is placed on a light box and a series of photographs taken to determine proper exposure (bracketing). An aperture setting of f8 or f11 with 1/2 second exposure time usually is appropriate.
Develop 8 minutes with a 1:80 dilution of Kodak HC-110 developer with occasional agitation. Rinse 3x with tap water, fix 5 minutes with occasional agitation, 1:7 dilution of Kodak fixer (as indicated in the flyer). Rinse 20 minutes, dip in PhotofloŞ solution before hanging to air dry. Print 4 x 5" copies, 1 of each gel per student.
To save printing costs and time use a digital camera to photograph gels. Advantages: saves development and printing time, saves costs of paper, images can be in color, printed images can be enlarged. Disadvantages: takes up computer space, there is some loss of resolution. Gels can also be scanned directly between two pieces of acetate, using a flatbed reflective scanner.
Power supplies must be capable of at least a 150 volt output, and a minimum of 100 mA (0.1A), 150 mA or more preferred, since one gel may draw 60 to 70 mA initially. Many supplies have a current limit of 0.1 A, and these make it difficult to run several gels quickly, since adding gels in parallel increases the required current output. The power supply should be fitted with at least two sets of outputs, preferably three or four. Alternatively, cables can be "piggy backed," but this might violate safety codes.
Cables should be 1 red, 1 black, male bannana connector for connection to the power supply and a female connector for hooking to the gel apparatus (or male/female connector at the other end for "piggyback" connections).